This manual is for C-INTERCAL version 0.29. It does not replace the old groff manual, nor is it designed to be read in conjunction with it; instead, it serves a different purpose, of providing information useful to users of C-INTERCAL (unlike the other manual, it is not derived from the original INTERCAL-72 manual).
Copyright © 2007 Alex Smith.
Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation; with no Invariant Sections, with no Front-Cover Texts, and with no Back-Cover Texts. A copy of the license is included in the section entitled “GNU Free Documentation License.”
This is the Revamped Instruction Manual for C-INTERCAL (this version is distributed with C-INTERCAL version 0.29). It is divided into four parts.
The first part is about the C-INTERCAL compiler ick, and how to use it. It covers installing the compiler, using the compiler, what error and warning messages are produced by the compiler, and some information on how to use the debugger.
The second part is about the core INTERCAL language, invented in 1972, and some other commands since then which don't feel like they're extensions. (This is a pretty arbitrary distinction, but people who write the documentation are entitled to arbitrary distinctions. The manual's licensed under a license that lets you change it (see Copying), so if you disagree you can move the commands from section to section yourself.) Mostly only commands that are implemented in C-INTERCAL are covered here (if you're interested in the other commands implemented in other compilers, read CLC-INTERCAL's documentation). However, a comprehensive guide to portability of these commands between C-INTERCAL and other INTERCAL compilers is given.
The third part covers the INTERCAL extensions and dialects that are implemented by C-INTERCAL, such as TriINTERCAL and Threaded INTERCAL. Again, extensions and dialects not implemented have been mostly left out.
The final part contains appendices (which were known as `tonsils' in the original INTERCAL manual), such as character sets used by INTERCAL, programs other than ick in the C-INTERCAL distribution, information on how to read and update the list of optimizer idioms used by the compiler, and the copyright.
The C-INTERCAL distribution is distributed in source code form; this means that before using it, you first have to compile it. Don't worry: if you have the right software, it's not at all difficult. Most Linux-based and UNIX-based computers are likely to have the software needed already; the software needed to compile source-distributed packages is also readily available for free for other operating systems. The following instructions will help you install the distribution in a method appropriate for your system.
(If you happen to be using Debian or Ubuntu, you can also obtain and install binaries with the command ‘sudo apt-get install intercal’, making the rest of this chapter redundant. If you do this, use Debian's bug tracker to report bugs, rather than reporting them directly to the maintainers.)
C-INTERCAL distributions have been stored in many different places over time; it can sometimes be hard to make sure that you are finding the most recent version. In order to make sure that you have the most recent version, the easiest way is to look at the alt.lang.intercal newsgroup; all releases of the C-INTERCAL compiler ought to be announced there. (If you are interested in what other INTERCAL compilers are available, it may also be worth looking there.) If you don't have access to a newsreader, your newsreader doesn't cover that newsgroup, or the distance between releases has been too large for your news server to keep the message, it's likely that you can find the announcement in an archive on the World Wide Web; at the time of writing (2007), the archives of the newsgroup are stored by Google Groups, and a search for ‘alt.lang.intercal’ there should tell you where to find a copy.
If you're looking for the latest version, note that the number after the dot represents the major version number; you want to maximise this in favour of the number before the dot, which is the bugfix level within a major version. (Major versions are released as version 0.whatever; if a new version comes out that fixes bugs but adds no new features, nowadays its number will be of the form 1.whatever, with the same major number. This has not always been the case, though.)
C-INTERCAL is distributed in compressed pax format; for instance, you may find it as a ‘.pax.lzma’ file if you have the unlzma decompression program (this is advised, as it's the smallest); ‘.pax.bz2’ is larger and ‘.pax.gz’ is larger still. Most computers can decompress files in this format, even if they don't realise it, because pax is forwards-compatible with tar; try renaming the extension from ‘.pax’ to ‘.tar’ after decompressing to see if you have a progam that can decompress it. (If you're wondering why such an apparently non-standard format is being used, this is is actually a case where C-INTERCAL is being perfectly nonstandard by conforming to the standards; tar is no longer specified by POSIX, and pax is its replacement. It's just that pax never really caught on.)
It doesn't matter where you extract the distribution file to: it's best if you don't put it anywhere special. If you aren't an administrator, you should extract the file to somewhere in your home directory (Linux or UNIX-like systems) or to your My Documents directory (recent versions of Windows; if you're using an older version, then you are an administrator, or at least have the same privileges, and can extract it anywhere). Some commands that you might use to extract it:
unlzma ick-0-29.pax.lzma
tar xvf ick-0-29.pax
or
bunzip2 ick-0-29.pax.bz2
tar xvf ick-0-29.pax
or
gunzip ick-0-29.pax.gz
tar xvf ick-0-29.pax
On most UNIX-based and Linux-based systems, tar will be available to unpack the
installation files once they've been uncompressed with
gunzip. (I've heard that
some BSD systems have pax
itself to decompress the files, although have not been able to
verify this; some Linux distributions also have pax in their package managers. Both tar and
pax should work fine, though.) gunzip is also likely to be available (and
bunzip2 and
unlzma are less likely,
but use those versions if you have them to save on your bandwidth);
if it isn't, you will need to download a copy from the Internet.
tar xzvf ick-0-29.pax.gz
or
tar xqvf ick-0-29.pax.bz2
If you are using the GNU version of tar (which is very likely on Linux), you
can combine the two steps into one as shown here, except when using
the lzma-compressed version.
djtar -x ick-0-29.pax.gz
On a DOS system, you will have to install DJGPP anyway to be able
to compile the distribution, and once you've done that you will be
able to use DJGPP's decompressing and unpacking utility to extract
the files needed to install the distribution. (You will need to
type this at the command line; on Windows 95 and later, try
choosing Run... from the start menu then typing cmd (or command if that fails) in the dialog box
that opens to get a command prompt, which you can exit by typing
exit. After typing any
command at a command line, press <RET> to tell the shell to
execute that command.)
Whatever method you use, you should end up with a directory created called ick-0.29; this is your main installation directory where all the processing done by the installation will be carried out. You will need to have that directory as the current directory during install (at the command prompt in all the operating systems I know, you can set the current directory by typing cd ick-0.29).
There are scripts included in the distribution to automate the process of installing, in various ways. The simplest method of installing is to use the following routine:
mkdir build
cd build
../configure
to build in a subdirectory of the distribution called “build”). You also specify where you want the files to be installed at this stage; the default of ‘/usr/local’ is good for many people, but you may want to install elsewhere (in particular, if you want to test out C-INTERCAL without installing it, create a new directory somewhere you own and specify that as the place to install it, so the install will actually just copy the files into the right structure for use instead of installing them). To specify a location, give the option --prefix=location to configure; for instance, configure --prefix=/usr would install in /usr.
On all systems, it's worth just trying this to see if it works. This requires a lot of software on your computer to work, but all of it is standard on Linux and UNIX systems. The first command is a shell-script which will analyse your system and set settings accordingly; it will explain what it's doing and what settings it detected, and create several files in the installation directory to record its results. (This is a configure script produced by the GNU autoconf (configure); its autoconf source code is available in the file configure.ac.) The second command actually compiles the source code to produce binaries; this takes the longest of any of the steps. You will see all the commands that it's running as it runs them. The third command will copy the files it's compiled to appropriate shared locations on your system so that anyone on the system can just use ick.
There may be various factors that prevent this simple installation method working. On a system not based on UNIX or Linux, you may find that you don't have some of the software required to run this (for instance, you may be missing the shell sh, and don't have the shell bash which can emulate it, and so can't run sh config.sh that depends on one of those shells being available) and so this method won't work for you. In such cases, one solution may be to install all the software required; the GNU project has a version of all the commands required, for instance, and there may be ports available for your operating system. However, the only software absolutely required is a C compiler (C-INTERCAL was designed to work with gcc and is tested mostly with that compiler, but in theory it should work with other C compilers too, and this is tested on occasion) and the associated software needed to compile C files to object files and executables, combine object files into libraries, etc.
Another possibility that might stop this process working is if your version of the relevant software is incompatible with the GNU versions that were used for testing. For instance, I have come across proprietary versions of lex that need directives in the source file to say in advance how much memory the lexer-generator needs to allocate. In such cases, pay attention to the error messages you're getting; normally they will suggest trivial modifications to the source files that will cause the compilation to work again.
Some Linux and UNIX systems (notably Debian and Ubuntu) don't have the required files for compilation installed by default. To install them, just download and install the required packages: for Ubuntu at the time of writing, they are ‘binutils’, ‘cpp’, ‘gcc’, ‘libc6-dev’, ‘make’ to compile C-INTERCAL, and if you want to modify it, you may also need ‘autoconf’, ‘automake’, ‘bison’, and ‘flex’. For debugging help, you may also want ‘gdb’, and to recompile the documentation, you may need ‘groff’, ‘tetex-bin’, ‘texinfo’, and ‘tidy’. Of course, if INTERCAL ever (the author of this sentence was going to write something like “becomes popular, someone will probably package up a compiler for Debian or Ubuntu anyway”, but at that point on a whim did an Ubuntu package search for 'intercal' and actually came up with two results, which look suspiciously like C-INTERCAL and CLC-INTERCAL, later confirming this. The author was vaguely aware that there was a CLC-INTERCAL package floating around, but was unaware of the C-INTERCAL package, and as a result was too surprised to finish the sentence.)
If you're trying to do something unusual, you probably want to set some of the settings yourself rather than letting the compilation process guess everything. In this case, use configure --help to view the options that you can set on configure; there's a wide range of settings that you can set available there, and one of them may be what you want.
It may happen that you decide to uninstall C-INTERCAL after installing it; this may be useful if you want to test the installation system, or change the location you install programs, or for some reason you don't want it on your computer. It's worth uninstalling just before you install a new version of C-INTERCAL because this will save some disk space; you cannot install two versions of C-INTERCAL at once (at least, not in the same directory; but you can change the –prefix of one of the installations to get two versions at once).
If you installed C-INTERCAL using make install, you can uninstall it by using make uninstall from the installation directory, assuming that it still exists. If you can't use that method for some reason, you can uninstall it by deleting the files ick and convickt where your computer installs binaries (with an extension like ‘.exe’ added if that's usual for binaries on your operating system), libick.a, libickmt.a, libickec.a, and libyuk.a where your computer installs libraries, and the subdirectories ick-0.29 in the places where your computer installs data files and include files, and their contents.
You can go further than uninstalling. Running make clean will delete any files created by compilation; make distclean will delete those files, and also any files created by configuring. It's probably a wise idea to uninstall before doing a distclean, though, as otherwise information needed to uninstall will be deleted, as that information is generated by configure.
If you can't get C-INTERCAL to install at all, or something goes wrong when you're using it, reporting a bug is probably a good idea. (This is still important even if you figure out how to fix it, and the information isn't in the manual, because the fix can be added to the source code if possible, or at least to the manual, to benefit future users.) For general help, you may want to post to the alt.lang.intercal news group; to report a bug or submit a patch, email the person who released the most recent C-INTERCAL version (which you can determine by looking at that newsgroup).
If you do find a bug (either the compiler not behaving in the way you'd expect, or if you find a way to cause E778 (see E778) without modifying the source code), it helps a lot if you can submit a bug report explaining what causes it. If you're not sure, say that; it helps if you give examples of input, command line options, etc. that cause the bug. There are several debug options (see Debug Options) that you can use to help pin down a bug if you're interested in trying to solve the problem yourself; looking at the output C code can also help pin down a bug if the compiler gets that far.
Information that should be given in a bug report is what you expect to happen, what actually happens, what input and command line options you gave to the compiler, what operating system you're using, any ideas you might have as to what the problem is, and any appropriate debug traces (for instance, -H (see -H) output if you think the bug is in the optimizer). Core dumps aren't portable between systems, so don't send those; however, if you're getting an internal error and can dump core with -U (see -U), it helps if you can load a debugger (such as gdb) on the core dump, use the debugger to produce a backtrace, and send that backtrace.
If you figure out how to solve the bug yourself, and want to submit the patches to help other users (this also carries the advantage that your patches will then be maintained along with the rest of the distribution, and that you won't have to reapply them every time you upgrade to a newer version of C-INTERCAL), you must first agree to license your code under the same license as the code that surrounds it (normally, that's the GNU General Public License, but if you submit a patch to a file with a different license, like this manual (yes, documentation patches are useful too), you must agree to that license). You will be credited for the patch in the source code unless you specifically ask not to be or you don't give your name (in both these cases, you must license the code to the public domain so that it can be incorporated without the attribution requirement). Preferably, patches should be submitted in the format created by the command diff -u; this command is likely to be available on UNIX and Linux systems and versions are also available for DOS and Windows (including a DJGPP port of the GNU version). If you can't manage that, just submit your new code with enough lines of old code around it to show where it's meant to go, and a description of approximately where in the file it was. Patches should be submitted by email to the person who most recently released a version of C-INTERCAL.
If you have a suggestion for a new feature, it makes sense to first discuss it on the alt.lang.intercal news group; other INTERCAL compiler maintainers may also want to implement that feature. If you have developed code to implement that feature in C-INTERCAL, you can submit it the same way that you would submit a patch for a bug.
Due to the licensing conditions of C-INTERCAL, you are allowed to release your own version or distribution if you want to. In such cases, it's recommended that you follow the following guidelines:
All operations on INTERCAL source code available in C-INTERCAL are currently carried out by the compiler ick.
The syntax is
ick -options inputfile
(Options can be given preceded by separate hyphens, or all in a row after one hyphen, or a mixture; they're all single characters.) By default, this compiles one INTERCAL program given as the input file directly to an executable without doing anything fancy; usually you will want to give options, which are described below.
The following command-line options to ick affect what dialect of the INTERCAL language is compiled by the compiler; you may need to set one or more of these options if your input is not the default C-INTERCAL but instead some other language like INTERCAL-72 or CLC-INTERCAL, or just because you like certainty or like being different with respect to your output. Note that there is no command-line option corresponding to TriINTERCAL (or the base 4-7 versions); instead, the numeric base to use is determined by looking at the filename extension (‘.i’ for base 2, the default, or ‘.3i’ to ‘.7i’ for the base 3-7 versions.)
# in your
program, not things like line numbers; you want Forte for that.) This option
also allows you to write arbitary expressions on the left of an
assignment statement if you wish.
? to be interpreted with Princeton
rather than Atari meanings.
Sometimes things will go wrong with your program, or with the way ick was installed. There may even be unknown bugs in ick itself (if you find one of these, please report it). The following options are used to debug the whole system on various levels.
WRITE IN instructions will often show up as
taking a long time due to their need to wait for input.
These options allow you to control how far to compile (all the way to an executable, or only to C, etc.), and where the output will be created. Note that the output options may change depending on the other options selected; for instance, many of the debug options will prevent the code being compiled all the way to an executable.
This option also places verbose comments in the output C file.
There are various command line options that can be used to tell ick whether and in what ways to optimize code.
ABSTAINED from and refrain from
generating code to check the abstention status of those commands.
Some options just can't be classified.
Once the compiler runs and produces an output executable, that executable itself will accept a range of options that control the way it runs. None of these options have to be used; a default value will be assumed if they aren't.
Various environment variables can be set to affect the operation of ick.
| Variable |
Meaning
|
|---|---|
|
ICKINCLUDEDIR
ICKLIBDIR ICKSYSDIR ICKCSKELDIR |
These four environment variables suggest locations in which
ick should look to find
various files that it needs: the skeleton file, system library, C
header files and libraries that it needs, constant-output
optimiser, and the GNU General Public License (which the debugger
needs to be able to display on demand for legal reasons).
|
| CC |
The name of a C compiler to use (defaults to gcc, which is the only
compiler with which C-INTERCAL has been tested
recently). This option has no effect on DJGPP, where gcc is always
used.
|
|
ICKTEMP
TMPDIR TEMP TMP |
On DJGPP, ick creates
temporary files to pass options to gcc as a method of getting
around the limit on the length of a command line that can sometimes
affect DOS programs. These four environment variables are tried (in
this order) to determine a location for the temporary file; if none
of them are set, the current directory is used.
|
Things may go wrong, either during the compilation or the execution of your program. Note that some things that would be compile-time errors in many other languages – such as syntax errors – are in fact run-time errors in INTERCAL.
Errors and warnings appear as an error code starting with
‘ICL’, followed by a
three digit number, followed by ‘I’ for an error or ‘W’ for a warning. However, they will be
notated here as ‘E000’, etc., to save space and because
consistency was never a strong point of INTERCAL.
This is followed by a text description of the error, and a hint as to
the location of the error. This is not the line on which the error
occurred, but rather the line on which the next command to be executed
is. To add to the fun, the calculation of the next command to be
executed is done at compile-time rather than runtime, so it may be
completely wrong due to things like abstention on COME
FROMs or computed COME FROMs. The moral of this
story is that, if you really want to know where the error is, use a
debugger. Note also that if the error happens at compile-time, there is
no guarantee that the line number given makes any sense at all. Some
errors don't give next line numbers, mostly those for which it doesn't
make logical sense, such as E633 (see E633). After
this is a suggestion to correct (or reconsider) the source code and to
resubnit it. (This typo has been carefully preserved for over a
decade.)
This is a list of the error messages that might be produced during the compilation or execution of an INTERCAL program.
ABSTAINed syntax
error, for instance, would not be executed; this is one of the
mechanisms available for writing comments.) The text of the error
message is simply the statement that couldn't be decoded.
DO YOU EXPECT ME TO FIGURE THIS OUT?
This error occurs when there is an attempt to use a constant with a
value outside the onespot range; it's a compile-time error.
PROGRAMMER IS INSUFFICIENTLY POLITE
The balance between various statement identifiers is important. If
less than approximately one fifth of the statement identifiers used
are the polite versions containing PLEASE, that causes
this error at compile time.
PROGRAMMER IS OVERLY POLITE
Of course, the same problem can happen in the other direction; this
error is caused at compile time if over about one third of the
statement identifiers are the polite form.
COMMUNIST PLOT DETECTED, COMPILER IS SUICIDING
This error happens when you give the -t option (see -t)
but you use a language construct that wasn't available in
INTERCAL-72. If this happens, then either there's a
mistake in the program that prevents it being
INTERCAL-72 or you shouldn't be compiling it as
INTERCAL-72 in the first place.
PROGRAM HAS DISAPPEARED INTO THE BLACK LAGOON
There is a hard limit of 80 NEXTs at a time; this is to discourage
excessive use of NEXTING
for things like recursion. (Recursive programs are entirely legal;
you simply have to figure out how to do it with computed
COME FROM instead. (For
the record, it is possible. (Using lots of nested brackets when
talking about recursion is great (yay!).))) Another problem with
writing the source code that can cause this error is a failure to
properly FORGET the entry
on the NEXT stack created
when trying to simulate a goto.
SAYING 'ABRACADABRA' WITHOUT A MAGIC WAND WON'T DO YOU ANY GOODYour program asked to include the system library (by specifying a line number from 1000 to 1999 inclusive without including a line with that number), but due to installation problems the compiler couldn't find the system library to include. You could try using the -u (see -u) option to see where the compiler's looking; that may give you an idea of where you need to copy the system library so that the compilation will work. This error happens at compile time and doesn't give a next command line number.
PROGRAM HAS GOTTEN LOST
This error happens at compile time when the compiler can't figure
out where a NEXT command is actually aiming (normally
due to a typo in either the line label given or the line label on
the line aimed for). The logic behind this error means that the
next line to be executed is unknown (after all, that's the whole
point of the error) and is therefore not given. The
-e command-line option
(see -e) makes this error into a run-time
error, because it allows NEXT commands to dynamically
change targets at runtime, as well as line labels to dynamically
change values, and thus the error is impossible to detect at
compile time.
I WASN'T PLANNING TO GO THERE ANYWAY
This error happens at compile time when an ABSTAIN or
REINSTATE references a non-existent target line. This
generally happens for much the same reasons as E129 (see E129).
YOU MUST LIKE THIS LABEL A LOT!
At present, it's impossible to have more than one line with the
same line number. That would make NEXT act too much
like COME FROM in reverse to be interesting. This
error happens at compile time. (For inconsistency, it is
possible to have multiple lines with the same number as long as at
most one of them is in an INTERCAL program (the
others have to be in programs in other languages included via the
external calls system).)
SO! 65535 LABELS AREN'T ENOUGH FOR YOU?
Legal values for line labels are 1 to 65535 (with values from 1000
to 1999 reserved if you want to use the system library, and 1600 to
1699 reserved if you're using other expansion libraries). This
error comes up if you use nonpositive or twospot values for a line
label.
NOTHING VENTURED, NOTHING GAINED
You used a variable that isn't actually in your program. Failing
that (which would be quite impressive and is probably impossible,
at least in the present version of C-INTERCAL), you
specified an illegal number for a variable (legal numbers are
positive and onespot). This error happens at compile time, at least
for illegal variable numbers.
BUMMER, DUDE!
In INTERCAL, you're allowed to
STASH as much as you like; this makes the language
Turing-complete and allows for unlimited recursion when combined
with computed COME FROM in the right way.
Unfortunately, real computers aren't so idealised; if you manage to
write a program so memory-intensive that the computer runs out of
memory to store stashes, it causes this error at runtime. To fix
this error, you either have to simplify the program or upgrade your
computer's memory, and even then that will only help to some
extent.
ERROR HANDLER PRINTED SNIDE REMARK
Arrays have to be large enough to hold at least one element; you
tried to dimension an array which isn't large enough to hold any
data. This error happens at run time.
VARIABLES MAY NOT BE STORED IN WEST HYPERSPACE
This error happens at run time when the subscripts given to an
array are inconsistent with the way the array was dimensioned,
either because there were the wrong number of subscripts or because
a subscript was too large to fit in the array. It can also happen
when a multidimensional array is given to a command, such as
WRITE IN, that expects it to be monodimensional.
I'VE FORGOTTEN WHAT I WAS ABOUT TO SAY
This run-time error message is caused by the compiler running out
of memory whilst trying to do I/O; at present, it can only happen
during CLC-INTERCAL-style I/O.
THAT'S TOO HARD FOR MY TINY BRAIN
Some commands simply aren't available in PIC-INTERCAL.
I mean, PICs generally have less than a kilobyte
of memory; you're not going to be able to use some of the more
confusing language features with that sort of resource limitation.
The solution is to replace the affected command, or to not give the
-P option (see -P) if you didn't mean to compile as
PIC-INTERCAL in the first place.
DON'T BYTE OFF MORE THAN YOU CAN CHEW
This error happens when there is an attempt to store a twospot
value in a onespot variable. The actual size of the value is what
matters when counting its spots; so you can store the output of a
mingle in a onespot variable if it happens to be less than or equal
to 65535, for instance. (This is not necessarily the case in
versions of INTERCAL other than
C-INTERCAL, though, so you have to be careful with
portability when doing this.)
YOU CAN ONLY DISTORT THE LAWS OF MATHEMATICS SO FAR
Reverse assignments are not always mathematically possible. Also, sometimes they require changing the value of a constant; this is only legal if you specifically specified that it was legal by using the -v option. In the case of an impossible reverse assignment (including a situation in which operand overloading causes a reverse assignment to happen), this error happens at runtime.
This error can also come up when a scalar variable is overloaded to
an array (which doesn't make sense, but could happen if someone
exploited bugs in the CREATE statement (see CREATE)), and an attempt is made to read or assign to
that variable. (Subscripting a scalar variable is a syntax error,
so there is no use for doing such an overload anyway.)
THAT MUCH QUOTATION AMOUNTS TO PLAGIARISM
There is a limit of 256 on the number of nested spark/ears groups
allowed. If you somehow manage to exceed that limit, that will
cause this error. Try breaking the expression up into smaller
expressions. (The limit is trivial to increase by changing
SENESTMAX in ick.h; if you ever actually come across a
program that hits the limit but wasn't designed to, just email the
maintainer to request a higher limit.)
YOU CAN'T HAVE EVERYTHING, WHERE WOULD YOU PUT IT?
Your program references so many variables that the compiler
couldn't cope. This error is unlikely to ever happen; if it does,
try reducing the number of variables you use by combining some into
arrays. This is a compile-time error.
THAT'S TOO COMPLEX FOR ME TO GRASP
This is another compile-time error that's unlikely to ever happen;
this one signifies the compiler itself running out of memory trying
to compile your program. The only solutions to this are to simplify
your program, or to make more memory available to the compiler.
I'M ALL OUT OF CHOICES!
Your program asked that a choicepoint be backtracked to or removed,
but there aren't any choicepoints at the moment. This runtime error
usually indicates a logic mistake in your program. In backtracking
programs translated from other backtracking languages, this
indicates that the program has failed.
PROGRAM REJECTED FOR MENTAL HEALTH REASONS
Your program used a construct that only makes sense when
multithreading or backtracking (WHILE,
MAYBE, GO BACK, or GO
AHEAD), but you didn't specify the -m option (see -m).
If you meant to write a multithreaded or backtracking program, just
give that option; if you didn't, be careful what words you use in
comments! This error happens at compile-time.
THROW STICK BEFORE RETRIEVING!
In order to RETRIEVE a variable, it has to be
STASHed first; if it isn't, then this error happens at
runtime.
IT CAME FROM BEYOND SPACE
A COME FROM aiming at a line label — as opposed
to a computed COME FROM, which is allowed to be
pointing at a nonexistent line — must point to a valid line
label. The same applies to NEXT FROM. This error
happens at compile time if a nonexistent line label is found in one
of these contexts.
YOU WANT MAYBE WE SHOULD IMPLEMENT 64-BIT VARIABLES?
This error is like E275 (see E275), but applies
when an attempt is made at runtime to store a threespot value (or
even a fourspot or morespot value) in a twospot variable, or a
threespot or greater value is produced as an intermediate during a
calculation (for instance by a mingle operation). No values above
twospot are allowed at any point during an
INTERCAL program; if you want to process higher
numbers, you have to figure out a different way of storing them.
BETTER LATE THAN NEVEROops! The compiler just noticed that it had a buffer overflow. (Normally programs catch buffer overflows before they happen; C-INTERCAL catches them just afterwards instead.) This only happens on systems which don't have a modern C standard library. Try using shorter or fewer filenames on the command line, to reduce the risk of such an overflow.
FLOW DIAGRAM IS EXCESSIVELY CONNECTED
Aiming two COME FROMs at the same line only makes
sense in a multithreaded program. In a non-multithread program,
doing that will cause this error at compile time (if neither
COME FROM is computed) or at run time (if the command
that has just finished running is simultaneously the target of two
or more COME FROMs). This either indicates an error in
your program or that you've forgotten to use the -m option (see -m)
if you are actually trying to split the program into two threads.
I DO NOT COMPUTE
The program asked for input, but for some reason it wasn't
available. (This is a runtime error, obviously.) The error may
happen because the input is being piped in from a command or file
which has reached end-of-file, or because the user typed
<CTRL>-<D> (UNIX/Linux) or
<CTRL>-<Z> (DOS/Windows) while the program
was trying to WRITE IN some data.
WHAT BASE AND/OR LANGUAGE INCLUDES string?
When reading spelt-out-digit input, the input didn't seem to be a
valid digit in English, Sanskrit, Basque, Tagalog, Classical
Nahuatl, Georgian, Kwakiutl, Volapük, or Latin. This seems to have
languages covered pretty well; what on earth were you using, or did
you just make a spelling mistake?
ERROR TYPE 621 ENCOUNTERED
The compiler encountered error E621 (see E621).
This happens at runtime when the program requests that no entries
are removed from the NEXT stack (which is possible),
but that the last entry removed should be jumped to (which given
the circumstances isn't, because no entries were removed).
THE NEXT STACK RUPTURES. ALL DIE. OH, THE EMBARRASSMENT!
When an attempt is made to RESUME past the end of the
NEXT stack, the program ends; however, this cause the
program to end in a manner other than via GIVE UP or
DON'T TRY AGAIN, so an error message must be printed,
and this is that error message.
PROGRAM FELL OFF THE EDGE
You can't just let execution run off the end of the program. At
least, that is, if it doesn't end with TRY AGAIN. An
attempt to do that causes this error at runtime. Note that if your
program references the system library, then it counts as being
appended to your program and so the program will run into the first
line of the system library rather than cause this error. As it
happens, the first line of the system library is a syntax error, so
doing this will cause E000 (see E000) with the
error text ‘PLEASE KNOCK BEFORE
ENTERING’. There isn't a next statement to be
executed with E633, so the next statement won't be given in the
error message.
HOW DARE YOU INSULT ME!
The PIN command doesn't make much sense for anything
bigger than a PIC; using it in a
non-PIC program causes this error at
compile-time. Try using the normal input and output mechanisms
instead. This error may also be a clue that you are trying to
compile a PIC-INTERCAL program without giving the
-P option (see -P).
COMPILER HAS INDIGESTION
There isn't a limit on the length of an input program other than
your computer's memory; if your computer does run out of memory
during compilation, it causes this error. This error can also be
caused if too many input files are specified on the command line;
if you suspect this is the problem, split the compilation into
separate compilations if you can, or otherwise you may be able to
concatenate together your input files into larger but fewer files.
Yet another potential cause of this error is if a line in an input
program is too long; sensible line-wrapping techniques are
encouraged.
RANDOM COMPILER BUG
No compiler is perfect; sometimes errors just happen at random. In
this case, the random error is E774. If you don't like the idea
that your program may be shot down by a random compiler bug, or you
are doing something important, you can use the -b option (see -b)
to prevent this bug happening. (You may wonder why this bug is in
there at all if it's so easily prevented. The answer is that such a
bug was present in the original INTERCAL-72 compiler,
which also had an option to turn the bug off. It's also a reward
for people who actually read the manual.)
A SOURCE IS A SOURCE, OF COURSE, OF COURSE
You specified a file to compile on the command line, but the
compiler couldn't find or couldn't open it. This is almost
certainly because you made a typo specifying the file.
UNEXPLAINED COMPILER BUG
This should never come up, either at compile time or at run time.
It could come up at either when an internal check by the compiler
or the runtime libraries realises that something has gone badly
wrong; mistakes happen, and in such cases the mistake will have
been detected. (If this happens at compile time you can use the
-U option (see -U) to cause the compiler to send an abort
signal – which normally causes a core dump – when the
error happens, to help debug what's causing it.) More often, this
error comes up when the operating system has noticed something
impossible, like an attempt to free allocated memory twice or to
write to a null pointer, and tells the compiler an error has
occured, in which case the same response of putting up this error
happens. The point is that in all cases this error indicates a bug
in the compiler (even if it happens at run time); in such cases, it
would be very helpful if you figure out what caused it and send a
bug report (see Reporting Bugs).
ARE ONE-CHARACTER COMMANDS TOO SHORT FOR YOU?
This is a debug-time error caused when you give too much input to
the debugger when all it wanted was to know what you wanted to do
next.
PROGRAM IS TOO BADLY BROKEN TO RUN
There's a limit to how many breakpoints you can have in a program;
you've broken the limit and therefore broken the debugger. This is
a debug-time error.
I HAVE NO FILE AND I MUST SCREAMThe output file couldn't be written, maybe because the disk is full or because there's already a read-only file with the same name. This is a compile-time error.
HELLO? CAN ANYONE GIVE ME A HAND HERE?This error occurs at compile-time if a file type was requested for which the required libraries are unavailable. (Support for Funge does not ship with the compiler; instead, you need to generate the library yourself from the cfunge sources. For more information, see Creating the Funge-98 Library.)
YOU HAVE TOO MUCH ROPE TO HANG YOURSELF
There is no limit on the number of threads or choicepoints that you
can have in a multithreaded or backtracking program (in a program
that isn't multithreaded or backtracking, these are obviously
limited to 1 and 0 respectively). However, your computer may not be
able to cope; if it runs out of memory in the multithreader, it
will cause this error at runtime.
FLAG ETIQUETTE FAILURE BAD SCOUT NO BISCUIT
This error occurs at runtime if an INTERCAL program was passed an
unknown option flag.
I GAVE UP LONG AGO
TRY AGAIN has to be the last command in a program, if
it's there at all; you can't even follow it by comments, not even
if you know in advance that they won't be REINSTATEd.
This error happens at compile time if a command is found after a
TRY AGAIN.
NOCTURNAL EMISSION, PLEASE LAUNDER SHEETS IMMEDIATELY
This error should never happen, and if it dies indicates a compiler
bug. It means the emitter function in the code degenerator has
encountered an unknown opcode. Please send a copy of the program
that triggered it to the INTERCAL maintainers.
DO YOU REALLY EXPECT ME TO HAVE IMPLEMENTED THAT?
Some parts of the code haven't been written yet. There ought to be
no way to cause those to actually run; however, if you do somehow
find a way to cause them to run, they will cause this error at
compile time.
ILLEGAL POSSESSION OF A CONTROLLED UNARY OPERATOR
Some operators (such as whirlpool (@) and sharkfin
(^)) only make sense in TriINTERCAL
programs, and some have a minimum base in which they make sense.
This error happens at compile-time if you try to use an operator
that conflicts with the base you're in (such as using
TriINTERCAL operators in an
INTERCAL program in the default base 2).
EXCUSE ME, YOU MUST HAVE ME CONFUSED WITH SOME OTHER COMPILER
This error occurs just before compile-time if a file is encountered
on the command line that C-INTERCAL doesn't recognise. (If this
error occurs due to a ‘.a’, ‘.b98’, ‘.c’, or ‘.c99’, then you forgot to enable the
external calls system using -e (see -e).)
NO SKELETON IN MY CLOSET, WOE IS ME!
The skeleton file ick-wrap.c or pickwrap.c is needed to be able to compile INTERCAL to C. If the compiler can't find it, it will give this error message. This indicates a problem with the way the compiler has been installed; try using the -u option (see -u) to find out where it's looking (you may be able to place a copy of the skeleton file in one of those places).
This is a list of the warnings stored in the warning database. Warnings only come up when the -l option (see -l) is given; even then, some of the warnings are not currently implemented and therefore will never come up.
DON'T TYPE THAT SO HASTILY
The positional precedence rules for unary operators are somewhat
complicated, and it's easy to make a mistake. This warning is meant
to detect such mistakes, but is not currently implemented.
THAT WAS MEANT TO BE A JOKE
If an INTERCAL expression has been translated
from another language such as C, the optimiser is generally capable
of translating it back into something similar to the original, at
least in base 2. When after optimisation there are still
INTERCAL operators left in an expression, then
this warning is produced. (Therefore, it's likely to come up quite
a lot if optimisation isn't used!) The system library produces some
of these warnings (you can tell if a warning has come up in the
system library because you'll get a line number after the end of
your program).
THAT RELIES ON THE NEW WORLD ORDER
This warning comes up whenever the compiler recognises that you've
added some code that didn't exist in INTERCAL-72. This
allows you to check whether your code is valid
INTERCAL-72 (although -t (see -t) is more
useful for that); it also warns you that code might not be portable
(because INTERCAL-72 is implemented by most
INTERCAL compilers, but more recent language
features may not be).
SYSLIB IS OPTIMIZED FOR OBUSCATION
There is an idiom used in the system library that does a
right-shift by selecting alternate bits from a twospot number and
then mingling them the other way round. A rightshift can much more
easily be done with a single rightshift, so this is a silly way to
do it, and this warning warns that this idiom was used. However,
the present optimizer is incapable of recognising whether this
problem exists or not, so the warning is not currently implemented.
YOU CAN'T EXPECT ME TO CHECK BACK THAT FAR
It's an error to assign a twospot value (a value over 65535) to a
onespot variable, or to use it as an argument to a mingle. If the
optimizer can't guarantee at compile time that there won't be an
overflow, it issues this warning. (Note that this doesn't
necessarily mean there's a problem — for instance, the system
library generates some of these warnings — only that the
optimiser couldn't work out for sure that there wasn't a problem.)
WARNING HANDLER PRINTED SNIDE REMARK
Your code looks like it's trying to assign 0 to an array, giving it
no dimension; this is an error. This warning is produced at compile
time if it looks like a line in your code will cause this error,
but it isn't necessarily an error because that line of code might
never be executed.
FROM A CONTRADICTION, ANYTHING FOLLOWS
It's sometimes impossible to reverse an assignment (a reverse
assignment can happen if the -v option (see -v)
is used and an expression is placed on the left of an assignment,
or in operand overloading); if the compiler detects that a reversal
failure is inevitable, it will cause this warning. Note that this
doesn't always cause an error, because the relevant code might
never be executed.
THE DOCUMENTOR IS NOT ALWAYS RIGHT
There is no way to get this warning to come up; it isn't even
written anywhere in C-INTERCAL's source code, is not
implemented by anything, and there are no circumstances in which it
is even meant to come up. It is therefore not at all obvious why it
is documented.
KEEP LOOKING AT THE TOP BIT
C-INTERCAL uses a slightly different typing mechanism
to some other INTERCAL compilers; types are
calculated at compile time rather than run time. This only makes a
difference in some cases involving unary operators. It's impossible
to detect at compile time for certain whether such a case has come
up or not, but if the compiler or optimizer thinks that such a case
might have come up, it will issue this warning.
WARNING TYPE 622 ENCOUNTERED
Your code looks like it's trying to resume by 0; this is an error. This warning is produced at compile time if it looks like a line in your code will cause this error, but it isn't necessarily an error because that line of code might never be executed.
The C-INTERCAL distribution contains a runtime debugger called `yuk'. Unlike most other debuggers, it is stored as object code rather than as an executable, and it is compiled into the code rather than operating on it. To debug code, add -y (see -y) to the command line of ick when invoking it; that tells it to compile the debugger into the code and then execute the resulting combination. (The resulting hybrid debugger/input executable is deleted afterwards; this is to prevent it being run by mistake, and to prevent spreading the debugger's licence onto the code it was compiled with.)
yuk can also be used as a profiler using the -p option (see -p); this produces a file yuk.out containing information on how much time was spent running each command in your program, and does not prompt for debugger commands.
Note that some command line arguments are incompatible with the debugger, such as -m and -f. In particular, this means that multithreaded programs and programs that use backtracking cannot be debugged using this method; the +printflow option (see +printflow) to a compiled program may or may not be useful for debugging multithreaded programs.
When the debugger starts, it will print a copyright message and a message on how to access online help; then you can enter commands to run/debug the program. The debugger will show a command prompt, ‘yuk007 ’, to let you know you can input a command.
Here are the commands available.
Commands are single characters followed by newlines, or followed by a
line number (in decimal) and a newline or a variable name (a
., ,, : or ;
followed by a number in decimal; note that some commands only allow
onespot and twospot variables as arguments).
| Command |
Description
|
|---|---|
| aLINE |
All non-abstained commands on line LINE become abstained
from once.
|
| bLINE |
A breakpoint is set on line LINE. The breakpoint causes
execution with ‘c’ to stop when it is reached.
|
| c |
The program is run until it ends (which also ends the debugger) or
a breakpoint is reached.
|
| dLINE |
Any breakpoint that may be on line LINE is removed.
|
| eLINE |
An explanation of the main expression in each command on line
LINE is printed to the screen. The explanation is in the
same format as the format produced by -h (see -h) and
shows what the optimiser optimised the expression to (or the
original expression if the optimiser wasn't used).
|
| fLINE |
Removes the effect of the ‘m’ command on line LINE.
|
| gLINE |
Causes the current command to be the first command on
LINE (if not on that line already) or the next command
on LINE, as if that line was NEXTed to and
then that NEXT stack item was forgotten.
|
| h |
Lists 10 lines either side of the current line; if there aren't 10
lines to one or the other side of the current line, instead more
lines will be shown on the other side to compensate, if available.
|
| iVAR |
Causes variable VAR to become IGNOREd,
making it read-only.
|
| jVAR |
Causes variable VAR to become REMEMBERed,
making it no longer read-only.
|
| k |
Continues executing commands until the NEXT stack is the same size or smaller than
it was before. In other words, if the current command is not a
NEXT and doesn't have a
NEXT FROM aiming at it,
one command is executed; but if a NEXT does happen, execution will continue
until that NEXT returns
or is forgotten. A breakpoint or the end of the program also end
this.
|
| lLINE |
Lists 10 lines of source code either side of line LINE,
the same way as with ‘h’, but using a line stated in the
command rather than the current line.
|
| mLINE |
Produces a message onscreen every time a command on line
LINE is executed, but without interrupting the program.
|
| n |
Show the NEXT stack on
the screen.
|
| o |
Continue executing commands until the NEXT stack is smaller than it was before.
If you are using NEXTs
like procedures, then this effectively means that the procedure
will run until it returns. A breakpoint or the end of the program
also end this.
|
| p |
Displays the value of all onespot and twospot variables.
|
| q |
Aborts the current program and exits the debugger.
|
| rLINE |
Reinstates once all abstained commands on line LINE.
|
| s |
Executes one command.
|
| t |
Continues execution until the end of the program or a breakpoint:
each command that executes is displayed while this command is
running.
|
| uLINE |
Continues execution of the program until just before a command on
line LINE is run (or a breakpoint or the end of the
program).
|
| vVAR |
Adds a `view' on variable VAR (which must be onespot or
twospot), causing its value to be displayed on the screen whenever
a command is printed on screen (for instance, because the command
has just been stepped past, or due to the ‘m’ or ‘t’ commands).
|
| w |
Displays the current line and current command onscreen.
|
| xVAR |
Removes any view and any action that may be associated with it on
variable VAR (which must be onespot or twospot).
|
| yVAR |
Adds a view on variable VAR; also causes a break, as if
a breakpoint was reached, whenever the value of that variable
changes.
|
| zVAR |
Adds a view on variable VAR; also causes a break, as if
a breakpoint was reached, whenever that variable's value becomes 0.
|
| VAR |
A onespot or twospot variable written by itself prints out the
value of that variable.
|
| <VAR |
WRITEs IN a new value for
variable VAR. Note that input must be in the normal
‘ONE TWO THREE’
format; input in any other format will cause error E579 (see
E579) and as that is a fatal error, the
debugger and program it's debugging will end.
|
| * |
Displays the license conditions under which ick is distributed.
|
| ? |
Displays a summary of what each command does.
(‘@’ does the
same thing.)
|
While the code is executing (for instance, during a ‘c’, ‘k’, ‘o’, ‘t’ or ‘u’ command), it's possible to interrupt it with <CTRL>-<C> (on UNIX/Linux) or <CTRL>-<BREAK> (on Windows/DOS); this will cause the current command to finish running and the debugger prompt to come back up.
INTERCAL programs consist of a list of statements. Execution of a program starts with its first statement; generally speaking each statement runs after the previous statement, although many situations can change this.
Whitespace is generally insignificant in INTERCAL programs; it cannot be added in the middle of a keyword (unless the keyword contains whitespace itself) or inside a decimal number, but it can be added more or less anywhere else, and it can be removed from anywhere in the program as well.
An INTERCAL statement consists of an optional line
label, a statement identifier, an optional execution chance, the
statement itself (see Statements), and
optionally ONCE or AGAIN.
The history of INTERCAL is plagued with multiple syntaxes and character sets. The result has settled down with two versions of the syntax; the original Princeton syntax, and the Atari syntax (which is more suited to the operating systems of today).
| INTERCAL-72 | C-INTERCAL | CLC-INTERCAL |
J-INTERCAL
|
|---|---|---|---|
| some versions | version 0.18+ | all versions |
no
|
The original INTERCAL-72 compiler was the Princeton compiler, which introduced what has become known as the Princeton syntax for INTERCAL; this is the syntax used in the original manual, for instance, and can be considered to be the `original' or `official' INTERCAL syntax. It is notable for containing various characters not found in some character sets; for instance, it writes the operator for mingle as a cent sign (known as `change'). The other operator that often causes problems is the bookworm operator ‘V’, backspace, ‘-’, which is used for exclusive-or; the backspace can cause problems on some systems (which was probably the original intention). This syntax is also the default syntax in the CLC-INTERCAL compiler, which is the de facto standard for expanding the Princeton syntax to modern INTERCAL features that are not found in INTERCAL-72; however, it does not appear to have been used as the default syntax in any other compilers. Nowadays, there are other ways to write the required characters than using backspace; for instance, the cent sign appears in Latin-1 and UTF-8, and there are various characters that approximate bookworms (for instance, CLC-INTERCAL uses the Latin-1 yen symbol for this, which just to make things confusing, refers to a mingle in modern Atari syntax).
| INTERCAL-72 | C-INTERCAL | CLC-INTERCAL |
J-INTERCAL
|
|---|---|---|---|
| some versions | yes | version 0.05+ |
yes
|
The other main syntax is the Atari syntax, so called because it was originally used by the “Atari implementation” of INTERCAL-72. It is not clear why the implementation was given this name, because the authors of the implementation are not known; it is not clear whether it has any connection with Atari other than running on an Atari computer, for instance. The syntax was designed to work better on ASCII-based systems, by avoiding the change character (although it can still be written as ‘c’, backspace, ‘/’, which the Atari compiler documentation claims that the Princeton compiler supported) in favour of a `big money' character (‘$’), and using the `what' (‘?’) as an alternative character for exclusive-or. This is the syntax that C-INTERCAL and J-INTERCAL have always used, and is the one most commonly used for communicating INTERCAL programs on Usenet and other similar fora (where ASCII is one of the most reliable-to-send character sets). It is also the syntax used for examples in this manual, for much the same reason. The Atari syntax for constructs more modern than INTERCAL-72 is normally taken to be that used by the C-INTERCAL compiler, because it is the only Atari-syntax-based compiler that contains non-INTERCAL-72 constructs that actually need their own notation.
| INTERCAL-72 | C-INTERCAL | CLC-INTERCAL |
J-INTERCAL
|
|---|---|---|---|
| yes | all versions | all versions |
all versions
|
The first part of an INTERCAL statement is a line label that specifies what its line number is. This is optional; it's allowed to have a statement without a line number, although that prevents other commands referring to it by number. Line numbers must be constants, and unique within the program. However, they do not have to be in order; unlike some other languages with line numbers, a line with a higher number can come earlier in the program than a line with a lower number, and the numbers don't affect the order in which commands are executed.
A line label is a integer expressed in decimal within a wax/wane pair
(( and )). For instance, this is a valid line
label:
(1000)
Note that line numbers from 1000 to 1999 are used by the system library, so using them within your own programs may produce unexpected errors if the system library is included. Apart from this, line numbers from 1 to 65535 are allowed.
It has become reasonably customary for people writing INTERCAL libraries to pick a range of 1000 line numbers (for instance, 3000 to 3999) and stick to that range for all line numbers used in the program (apart from when calling the system library), so if you want to write an INTERCAL library, it may be a good idea to look at the existing libraries (in the pit/lib directory in the C-INTERCAL distribution) and choose a range of numbers that nobody else has used. If you aren't writing a library, it may be a good idea to avoid such number ranges (that is, use only line numbers below 1000 or very high numbers that are unlikely to be used by libraries in the future), so that you can easily add libraries to your program without renumbering in the future.
| INTERCAL-72 | C-INTERCAL | CLC-INTERCAL |
J-INTERCAL
|
|---|---|---|---|
| yes | all versions | all versions |
all versions
|
After the line label (if a statement has one) comes the statement identifier, which marks where the statement starts. Either the label or the statement identifier, whichever one comes first, marks where the preceding statement finishes.
The main
statement identifier is DO. It also has two synonyms,
PLEASE and PLEASE DO; these synonyms are the
'polite' forms of statement identifiers. Although the three identifiers
have the same meaning, using either polite or non-polite identifiers
too much can cause an error; the correct proportion is approximately 3
non-polite identifiers for every polite identifier used. None of these
identifiers actually does anything else apart from marking where the
statement starts; they leave the statements in the default `reinstated'
state.
Adding
NOT or N'T to the end of any of these
identifiers, to create a statement identifier such as DO
NOT or PLEASE DON'T, also creates a valid statement
identifier. These differ in meanings from the previous set of
identifiers, though; they cause the statement they precede to not be
executed by default; that is, the command will be skipped during
execution (this is known as the `abstained' state). This applies even
if the command in question is in fact a syntax error, thus causing this
to be a useful method of writing comments. One common idiom is to write
code like this:
PLEASE NOTE: This is a comment.
The statement identifier (PLEASE NOT) is the only part of
this statement that is valid INTERCAL; however,
because the statement identifier is in the negated form that contains
NOT, the syntax error won't be executed, and therefore
this is a valid statement. (In INTERCAL, syntax
errors happen at runtime, so a program containing a statement like
DOUBT THIS WILL WORK will still compile, and will not end
due to the syntax error unless that statement is actually executed. See
E000.)
The ABSTAIN and REINSTATE statements can
override the NOT or otherwise on a statement identifier;
see ABSTAIN.
In backtracking programs, MAYBE is also a valid statement
identifier; see MAYBE. It comes before the other
keywords in the statement identifier, and an implicit DO
is added if there wasn't one already in the statement identifier (so
MAYBE, MAYBE DO, MAYBE DON'T,
MAYBE PLEASE, and so on are all valid statement
identifiers).
| INTERCAL-72 | C-INTERCAL | CLC-INTERCAL |
J-INTERCAL
|
|---|---|---|---|
| yes | all versions | version 0.02+ |
all versions
|
It's possible to specify that a command should be run only a certain
proportion of the time, at random. This is a rarely used feature of
INTERCAL, although it is the only way to introduce
randomness into a program. (The C-INTERCAL compiler
approximates this with pseudorandomness.) An execution chance
specification comes immediately after the statement identifier, but
before the rest of the statement, and consists of a double-oh-seven
(%) followed by an integer from 1 to 99 inclusive, written
in decimal; this gives the percentage chance of the statement running.
The execution chance only acts to prevent a statement running when it
otherwise would have run; it cannot cause a statement that would
otherwise not have run to run. For instance, the statement DO %40
WRITE OUT #1 has a 40% chance of writing out
‘I’, but the
statement DON'T %40 WRITE OUT #1 has no chance of writing
out I or anything else, because the N'T
prevents it running and the double-oh-seven cannot override that.
| INTERCAL-72 | C-INTERCAL | CLC-INTERCAL |
J-INTERCAL
|
|---|---|---|---|
| no | version 0.25+ | no |
no
|
The last part of a statement is an optional ONCE or
AGAIN. ONCE specifies that the statement is
self-abstaining or self-reinstating (this will be explained below);
AGAIN specifies that the statement should behave like it
has already self-reinstated or self-abstained. Whether the behaviour is
self-abstention or self-reinstatement depends on whether the statement
was initially abstained or not; a ONCE on an initially
reinstated statement or AGAIN on an initially abstained
statement indicates a self-abstention, and a ONCE on an
initially abstained statement or AGAIN on an initially
reinstated statement indicates a self-reinstatement.
The first time a self-abstaining statement is encountered, it is
executed as normal, but the statement is then abstained from and
therefore will not run in future. Likewise, the first time
self-reinstating statement is encountered, it is not executed (as is
normal for an abstained statement), but then becomes reinstated and
will run in future. In each of these cases, the ONCE
effectively changes to an AGAIN; the ONCE
only happens once, as might be expected.
REINSTATING a currently abstained self-abstaining
statement or ABSTAINING (that is, with the
ABSTAIN or REINSTATE commands) a currently
reinstated self-reinstating statement causes the AGAIN on
the statement to change back into a ONCE, so the statement
will again self-abstain or self-reinstate. Likewise,
REINSTATING a currently abstained self-reinstating
statement or ABSTAINING a currently reinstated
self-abstaining statement causes its ONCE to turn into an
AGAIN.
Historical note: ONCE was devised by Malcom Ryan as a
method of allowing synchronisation between threads in a multithreaded
program (ONCE is atomic with the statement it modifies,
that is, there is no chance that threads will change between the
statement and the ONCE). AGAIN was added to
Malcom Ryan's Threaded Intercal standard on the suggestion of Kyle
Dean, as a method of adding extra flexibility (and to allow the
ONCEs to happen multiple times, which is needed to
implement some multithreaded algorithms).
Many INTERCAL statements take expressions as arguments. Expressions are made up out of operands and operators between them. Note that there is no operator precedence in INTERCAL; different compilers resolve ambiguities different ways, and some versions of some compilers (including the original INTERCAL-72 compiler) will cause error messages on compiling or executing an ambiguous expression, so it's safest to fully group each expression.
| INTERCAL-72 | C-INTERCAL | CLC-INTERCAL |
J-INTERCAL
|
|---|---|---|---|
| yes | all versions | all versions |
all versions
|
The basic operands in INTERCAL are constants and variables. These together make up what in other languages are known as `lvalues', that is, operands to which values can be assigned. (Constants can also be lvalues in INTERCAL, but by default C-INTERCAL turns this off because it carries an efficiency penalty and can be confusing; this can be turned on with the -v option (see -v).)
Constants can have any integer value from 0 to 65535 inclusive; higher
values (up to 4294967295) can be generated in programs, but cannot be
specified literally as constants. (The usual way to work around this
limitation is to interleave two constants together; see Mingle.) A constant is written as a mesh (#)
followed by a number in decimal. At the start of the program, all
constants have the same value as the number that identifies them; for
instance, #100 has 100 as its value, and it's strongly
advised not to change the value of a constant during the execution of a
program.
There are four types of variable: 16-bit and 32-bit unsigned integers,
and arrays of 16-bit and 32-bit unsigned integers. These are
represented with a spot, twospot, tail, and hybrid (.,
:, ,, and ;) respectively. For
this reason, integers within the range 0 to 65535 inclusive are known
as `onespot numbers', and integers within the range 0 to 4294967295
inclusive are known as `twospot numbers'; variables with those ranges
are known as onespot and twospot variables. (Note that arrays did not
work in C-INTERCAL before version 0.7.)
Variables are represented with a character representing their data
type, followed by an integer from 1 to 65535 inclusive, written in
decimal. Non-array variables don't need to be declared before they are
used; they automatically exist in any program that uses them. For
instance, .1 and .001 are the same variable,
onespot number 1. Array variables need to be dimensioned before they
are used, by assigning dimensions to them; see Calculate.
Because there are no operator precedences in INTERCAL, there are various solutions to specifying what precedences actually are.
') or rabbit-ears ("), the
same way as wax/wane pairs (parentheses) are used in other
programming languages. INTERCAL-72 and earlier
C-INTERCAL versions demanded that expressions were
grouped fully like this, and this practice is still recommended
because it leads to portable programs and is easier to understand.
Whether sparks or rabbit-ears (often called just `ears' for short)
are used normally doesn't matter, and programmers can use one or the
other for clarity or for aesthetic appeal. (One common technique is
to use just sparks at the outermost level of grouping, just ears at
the next level, just sparks at the next level, and so on; but
expressions like ''#1~#2'~"#3~#4"'~#5 are completely
unambiguous, at least to the compiler.)
There are, however, some complicated situations involving array subscripting where it is necessary to use sparks and ears at alternate levels, if you want to write a portable program. This limitation is in C-INTERCAL to simplify the parsing process; INTERCAL-72 has the same limitation, probably for the same reason. Compare these two statements:
DO .1 <- ,3SUB",2SUB.1".2
DO .1 <- ,3SUB",2SUB.1".2~.3"".4
The problem is that in the first statement, the ears close a group, and in the second statement, the ears open a group, and it's impossible to tell the difference without unlimited lookahead in the expression. Therefore, in similar situations (to be precise, in situations where a group is opened inside an array subscript), it's necessary to use the other grouping character to the one that opened the current group if you want a portable program.
One final comment about sparks and rabbit-ears; if the next
character in the program is a spot, as often happens because
onespot variables are common choices for operands, a spark and the
following spot can be combined into a wow (!).
Unfortunately, none of the character sets that
C-INTERCAL accepts as input (UTF-8, Latin-1, and
ASCII-7) contain the rabbit character, although the Hollerith input
format that CLC-INTERCAL can use does.
.1~.2~.3 is
equivalent to .1~'.2~.3'. C-INTERCAL
versions 0.26 and later also right-associate binary operators so as
to produce the same results as CLC-INTERCAL rules in
this situation, but as nobody has yet tried to work out what the
other implications of CLC-INTERCAL rules are they are
not emulated in C-INTERCAL, except possibly by chance.
& to
the variable :1, write :&1, and to
portably apply it to the expression '.1~.2', write
'&.1~.2'.) CLC-INTERCAL, and versions
of C-INTERCAL from 0.26 onwards, allow the `prefix'
position of a unary operator, which is just before whatever it
applies to (as in &:1). This leads to ambiguities as
to whether an operator is prefix or infix. The portable solution is,
of course, to use only infix operators and fully group everything,
but when writing for recent versions of C-INTERCAL, it's
possible to rely on its grouping rule, which is: unary operators are
interpreted as infix where possible, but at most one infix operator
is allowed to apply to each variable, constant, or group, and infix
operators can't apply to anything else. So for instance, the
C-INTERCAL '&&&.1~.2' is
equivalent to the portable '&"&.&1"~.2' (or
the more readable version of this,
"&'"&.&1"~.2'", which is also portable). If
these rules are counter-intuitive to you, remember that this is
INTERCAL we're talking about; note also that this
rule is unique to C-INTERCAL, at least at the time of
writing, and in particular CLC-INTERCAL is likely to
interpret this expression differently.
Operators are used to operate on operands, to produce more complicated expressions that actually calculate something rather than just fetch information from memory. There are two types of operators, unary and binary operators, which operate on one and two arguments respectively. Binary operators are always written between their two operands; to portably write a unary operator, it should be in the `infix' position, one character after the start of its operand; see Prefix and infix unary operators for the full details of how to write unary operators portably, and how else you can use them if you aren't aiming for portability. This section only describes INTERCAL-72 operators; many INTERCAL extensions add their own operators.
| INTERCAL-72 | C-INTERCAL | CLC-INTERCAL |
J-INTERCAL
|
|---|---|---|---|
| yes | all versions | all versions |
all versions
|
Mingle, or interleave, is one of the two binary operators in INTERCAL-72. However, different INTERCAL compilers represent it in different ways, so it is impossible to write a mingle in a program completely portably, because it differs between Princeton and Atari syntax, and worse, the sequence of character codes needed to represent it in each syntax has varied from compiler to compiler.
The original INTERCAL-72 compiler (the Princeton compiler)
used the 'change' (cent) character for a mingle, represented as
c, backspace, /. (By the way, this is still
the most portable way to write a mingle; both C-INTERCAL
and CLC-INTERCAL accept it, at least if a lowercase
c is used, the Atari compiler accepted it, and its
documentation claimed that the Princeton compiler also accepted it;
CLC-INTERCAL also accepts a capital C before
the backspace and /, and allows | rather than
/.) The Atari compiler, another INTERCAL-72
compiler, used a 'big money' character ($) as the mingle
character; this character is also the only one accepted for mingle by
the J-INTERCAL compiler. C-INTERCAL
originally also used the $ character for mingle, and this
character is the one most commonly seen in existing
C-INTERCAL programs, and most often used when giving
examples of INTERCAL on Usenet, because it exists in
the ASCII-7 character set, and because it doesn't contain control
characters. From version 0.18 of C-INTERCAL onwards,
various other units of currency (change, quid, and zlotnik if Latin-1
is used as the input, and euro if Latin-9 is used as the input) are
accepted; from version 0.20 onwards, in addition to the Latin-1
characters, all the currency symbols in Unicode are accepted if UTF-8
is used as the input format. CLC-INTERCAL has always used
the change character (either the Latin-1 version or the version that
contains a backspace) for mingle. In this manual, mingle will be
represented as $, but it's important to bear in mind that
this character is not the most portable choice.
The mingle operator should be applied to two operands or expressions. To be portable, the operands must both be onespot expressions, that is expressions which have a 16-bit result; C-INTERCAL relaxes this rule slightly and only requires that the result be in the onespot range. (This is because the data type of a select operator's value is meant to be determined at runtime; C-INTERCAL determines all data types at compile time, so has to guess a 32-bit result for a select with a 32-bit type as its right operand even when the result might actually turn out to be of a 16-bit type, and so this behaviour prevents an error when a select operation returns a value with a 16-bit data type and is used as an argument to a mingle.) The result is a 32-bit value (that is, it is of a 32-bit data type, even if its value fits into the onespot range), which consists of bits alternated from the two arguments; to be precise, its most significant bit is the most significant bit of its first argument, its second most significant bit is the most significant bit of its second argument, its third most significant bit is the second most significant bit of its first argument, and so on until its least significant bit, which is the least significant bit of its second argument.
One of the most common uses of interleaving is to create a constant
with a value greater than 65535; for instance, 65536 is
#0$#256. It is also commonly used in expressions that need
to produce 32-bit results; except in some simple cases, this is usually
coded by calculating separately the odd-numbered and even-numbered bits
of the result, and mingling them together at the end. It is also used
in expressions that need to left-shift values or perform similar
value-increasing operations, as none of the other operators can easily
do this; and mingle results are commonly used as the argument to unary
binary logic operators, because this causes them to behave more like
the binary logic operators found in some other languages.
| INTERCAL-72 | C-INTERCAL | CLC-INTERCAL |
J-INTERCAL
|
|---|---|---|---|
| yes | all versions | all versions |
all versions
|
The select operator is one of the two binary operators in
INTERCAL-72; unlike mingle, every known implementation of
INTERCAL ever has used the sqiggle character
(~) as the representation of the select operator, meaning
that writing it portably is easy.
The select operator takes two arguments, which can be of either
datatype (that is, 16- or 32-bit). It returns a value made by selecting
certain bits of its first operand indicated by the second operand, and
right-justifying them. What it does is that it ignores all the bits of
the first operand where the second operand has a 0 as the corresponding
bit, that is, deletes them from a copy of the operand's value; the bits
that are left are squashed together towards the least-significant end
of the number, and the result is filled with 0s to make it up to 16 or
32 bits. (In INTERCAL-72 the minimum multiple of 16 bits
possible that the result fits into is chosen, although if :1 has the
value 131061 (in hex, 1FFFF) the expression #21~:1
produces a 32-bit result because 17 bits were selected, even though
many of the leading bits were zeros; in C-INTERCAL the
data type of the result is the same as of the right operand of the
select, so that it can be determined at compile time, and so using a
unary binary logic operator on the result of select when the right
operand has a 32-bit type is nonportable and not recommended.) As an
example, #21~:1 produces 21 as its result if :1 has the
value 131061, 10 as its result if :1 has the value 30 (1E in hex; the
least significant bit of 21 is removed because it corresponds to a 0 in
:1), and 7 as its result if :1 has the value 21 (because three bits in
21 are set, and those three bits from 21 are therefore selected by 21).
Select is used for right-shifts, to select every second bit from a number (either to produce what will eventually become an argument to mingle, or to interpret the result of a unary binary logic operator, or occasionally both), to test if a number is zero or not (by selecting it from itself and selecting 1 from the result), in some cases as a limited version of bitwise-and (that only works if the right operand is 1 less than a power of 2), and for many other purposes.
| INTERCAL-72 | C-INTERCAL | CLC-INTERCAL |
J-INTERCAL
|
|---|---|---|---|
| yes | all versions | all versions |
all versions
|
There are three unary operators in INTERCAL-72, each of
which carries out a binary logic operation on adjacent bits of the
number. The operators are and, or, and exclusive or; and and or are
represented by an ampersand (&) and book
(V) respectively, and exclusive or has the same notational
problems as mingle, as it differs between Princeton and Atari syntax.
It was represented by a bookworm, written V, backspace,
-, in the Princeton INTERCAL-72
implementation, and this is still the most portable way to write it
(C-INTERCAL and CLC-INTERCAL accept it). The
Atari implementation of INTERCAL-72 wrote it with a what
(?), and this is the representation originally used by
C-INTERCAL (and still accepted), the only representation
accepted by J-INTERCAL, the one most commonly used on
Usenet, and the one used in this manual (although again, it's worth
pointing out that this isn't portable). CLC-INTERCAL
approximates a bookworm with the yen character, which being a currency
character is one of the possible representations for mingle in
C-INTERCAL; C-INTERCAL uses the rather
confusing method of interpreting a yen character as exclusive-or if
input in Latin-1 but as mingle if input in UTF-8. (This usually does
the right thing, because CLC-INTERCAL doesn't support
UTF-8.) In the same way, CLC-INTERCAL has a
C-INTERCAL compatibility option to allow the use of
? for exclusive-or.
The operators take each pair of consecutive bits in their arguments
(that is, the least significant with the second least significant, the
second least significant with the third least significant, the third
least significant with the fourth least significant, and so on, with
the pair consisting of the most significant and least significant being
used to calculate the most significant bit of the result), and perform
an appropriate logic operation on them; and sets a bit of the result if
and only if both bits in the pair were set, or sets each bit
corresponding to each pair where either bit was set, and exclusive or
sets if and only if the bits in the pair had different values (that is,
one was set, but not both). So for instance, #&26 is
16 (26 is 1A in hexadecimal or 11010 in binary); #V26 is
31 (11111 in binary), and #?26 is 23 (10111 in binary).
The most commonly seen use for these operators is to carry out bitwise ands, ors, and exclusive ors between two different 16-bit expressions, by mingling them together, applying a unary binary logic operator, and selecting every second bit of the result; such code often results due to people thinking in terms of some other language when writing INTERCAL, but is still often useful. (Historically, the first idiom added to the optimizer, apart from constant folding, was the mingle/unary/select sequence.) There are more imaginative uses; one impressive example is the exclusive or in the test for greater-than from the original INTERCAL-72 system library:
DO :5 <- "'?":1~'#65535$#0'"$":2~'#65535$#0'"'
~'#0$#65535'"$"'?":1~'#0$#65535'"$":2~'#0$
#65535'"'~'#0$#65535'"
DO .5 <- '?"'&"':2~:5'~'"'?"'?":5~:5"~"#65535~
#65535"'~'#65535$#0'"$#32768'~'#0$#65535'"
$"'?":5~:5"~"#65535$#65535"'~'#0$#65535'"'
"$"':5~:5'~#1"'~#1"$#2'~#3
The first statement works out the value of :1 bitwise exclusive or :2; the second statement then works out whether the most significant set bit in :5 (that is, the most significant bit that differs between :1 and :2) corresponds to a set bit in :2 or not. In case that's a bit too confusing to read, here's the corresponding optimizer idiom (in OIL):
((_1~:2)~((?32(:2~:2))^#2147483648))->(_1>(:2^_1))
(Here, the ^ refers to a bitwise exclusive or, an operation found in OIL but not in INTERCAL, which is why the INTERCAL version is so much longer.) The INTERCAL version also has some extra code to check for equality and to produce 1 or 2 as the output rather than 0 or 1.
| INTERCAL-72 | C-INTERCAL | CLC-INTERCAL |
J-INTERCAL
|
|---|---|---|---|
| yes | version 0.7+ | all versions |
all versions
|
In order to access the elements of an array, either to read or write
the array, it is necessary to use the array subscript operator
SUB. Note that an array element is not a variable, so it
is not accepted as an acceptable argument to statements like
IGNORE; however, it can be assigned to.
The syntax for an array element is the array, followed by the keyword
SUB, followed by an expression for the element number in
the array. In the case of a multidimensional array, more than one
expression is given after the keyword SUB to give the
location of the element in each of the array's dimensions. The first
element in an array or array dimension is numbered 1.
For instance, this is a legal (but not particularly useful) INTERCAL program with no syntax errors that shows some of the syntaxes possible with array subscripting:
PLEASE ,1 <- #2 DO .1 <- #2 DO ,1 SUB .1 <- #1 DO ,1 SUB #1 <- ,1 SUB #2 PLEASE ;1 <- #2 BY #2 DO ;1 SUB #1 #2 <- ,1 SUB ,1 SUB .1 DO READ OUT ;1SUB#1.1 DO GIVE UP
Grouping can get complicated when nested array subscripting is used, particularly with multiple subscripts. It is the programmer's job to write an unambiguous statement, and also obey the extra grouping rules that apply to array subscripts; see Grouping Rules.
There is a wide range of statements available to INTERCAL programs; some identifiably belong to a particular variant or dialect (such as Backtracking INTERCAL), but others can be considered to be part of the 'core language'. The statements listed here are those that the C-INTERCAL compiler will accept with no compiler switches to turn on particular dialect options. Note that many statements have slightly different effects in different implementations of INTERCAL; known incompatibilities are listed here, but it's important to check your program on multiple compilers when attempting to write a portable program.
| INTERCAL-72 | C-INTERCAL | CLC-INTERCAL |
J-INTERCAL
|
|---|---|---|---|
| yes | version 0.15+ | all versions |
all versions
|
One of the more commonly-used commands in INTERCAL is the syntax error. A properly-written syntax error looks nothing like any known INTERCAL command; a syntax error that looks vaguely like a command but isn't may confuse C-INTERCAL before version 0.28, and possibly other compilers, into bailing out at compile time in some situations (this is known as a `serious syntax error'), and so is not portable. For other syntax errors, though, the semantics are easily explained: there is a run-time error whenever the syntax error is actually executed, and the line containing the syntax error is used as the error message.
One purpose of this is to allow your programs to produce their own custom errors at run time; however, it's very important to make sure that they start and end in the right place, by manipulating where statement identifiers appear. Here's a correct example from the system library:
DOUBLE OR SINGLE PRECISION ARITHMETIC OVERFLOW
This is a valid INTERCAL command, that produces an
error when run (note the DO at the start). An even more
common use is to produce an initially abstained syntax error by using
an appropriate statement identifier, for instance
PLEASE NOTE THAT THIS IS A COMMENT
This would produce an error if reinstated somehow, but assuming that
this isn't done, this is a line of code that does nothing, which is
therefore equivalent to a comment in other programming languages. (The
initial abstention is achieved with the statement identifier
PLEASE NOT; the extra E causes the command to
be a syntax error, and this particular construction is idiomatic.)
Referring to the set of all syntax errors in a program (or the set of
all commands of any other given type) is achieved with a special
keyword known as a `gerund'; gerund support for syntax errors is
resonably recent, and only exists in CLC-INTERCAL (version
1.-94.-3 and later, with COMMENT, COMMENTS,
or COMMENTING), and C-INTERCAL
(COMMENT in version 0.26 and later, and also
COMMENTS and COMMENTING in version 0.27 and
later). Therefore, it is not portable to refer to the set of all syntax
errors by gerund; using a line label is a more portable way to refer to
an individual syntax-error command.
| INTERCAL-72 | C-INTERCAL | CLC-INTERCAL |
J-INTERCAL
|
|---|---|---|---|
| yes | all versions | all versions |
all versions
|
At present, the only INTERCAL command that contains
no keywords (apart from the statement identifier and possibly
ONCE or AGAIN) is what is known as the
`calculate' command. It is used to assign values to variables, array
elements, and arrays; assigning a value to an array changes the number
of elements that that array can hold, and causes the values of all
elements previously in that array to be lost. The syntax of a calculate
command is as follows:
DO .1 <- ':2~:3'~#55
That is, the command is written as a variable or array element, then
the <- operator (known as an `angle-worm' and
pronounced `gets'), then an expression to assign to it. In the special
case when an array is being dimensioned by assigning a value to it, the
expression can contain the keyword BY to cause the array
to become multidimensional; so for a 3 by 4 by 5 array, it would be
possible to write
DO ,1 <- #3 BY #4 BY #5
The calculate command always evaluates the expression, even if for some reason the assignment can't be done (for instance, if the variable being assigned to is read-only); this is important if the expression has side-effects (for instance, giving an overflow error). If the variable does happen to be read-only, there is not an error; the expression being assigned to it is just evaluated, with the resulting value being discarded.
The gerund to refer to calculations is CALCULATING;
however, if you are planning to use this, note that a bug in older
versions of C-INTERCAL means that assignments to arrays
are not affected by this gerund before version 0.27.
CLC-INTERCAL from 1.-94.-4 onwards, and
C-INTERCAL from 0.26 onwards, allow arbitrary expressions
on the left hand side of an assignment (C-INTERCAL only if
the -v option is used); for more information on how such
`reverse assignments' work, see Operand
Overloading.
| INTERCAL-72 | C-INTERCAL | CLC-INTERCAL |
J-INTERCAL
|
|---|---|---|---|
| yes | all versions | see text |
all versions
|
The only flow-control commands in INTERCAL-72 were
NEXT, RESUME, and FORGET;
together these manipulate a stack of locations in the program known as
the `NEXT stack'. Although all INTERCAL compilers
have implemented these, from CLC-INTERCAL version 0.05
onwards CLC-INTERCAL has considered them obsolete, and
therefore a special command-line switch needs to be used to enable
them. (They are still the most portable flow-control commands currently
available, though, precisely because INTERCAL-72
implements nothing else.) Note that there is a strict limit of 80
locations on the NEXT stack, enforced by all known
INTERCAL compilers; this helps to enforce good
programming style, by discouraging NEXT-stack leaks (which are
otherwise quite easy to write).
Here are examples to show the syntax of these three statements:
DO (1000) NEXT DO FORGET '.1~.1'~#1 DO RESUME .5
The NEXT command takes a line label as its argument
(unlike most other INTERCAL commands, it comes after
its argument rather than before); both FORGET and
RESUME take expressions. (CLC-INTERCAL from
version 0.05 onwards also allows an expression in NEXT,
rather than a label, to give a computed NEXT, but this
behaviour was not implemented in other compilers, and is deprecated in
CLC-INTERCAL along with noncomputed NEXT; if
computed NEXT is ever implemented in
C-INTERCAL, it will likely likewise be deprecated upon
introduction). (Update: it was implemented in C-INTERCAL
version 0.28, but only as part of the external calls system, so it
cannot be used in ordinary programs; a sample expansion library gives
in-program access to a limited form of computed NEXT, but
should probably not be used.) Running a NEXT causes the
program control to transfer to the command whose line label is
referenced, and also saves the location in the program immediately
after the NEXT command on the top of the NEXT stack.
In order to remove items from the NEXT stack, to prevent
it filling up (which is what happens with a naive attempt to use the
NEXT command as an equivalent to what some other languages
call GOTO), it is possible to use the FORGET or
RESUME commands. They each remove a number of items from
the NEXT stack equal to their argument; RESUME also
transfers control flow to the last location removed from the
NEXT stack this way. Trying to remove no items, or more
items than there are in the stack, does not cause an error when
FORGET is used (no items or all the items are removed
respectively); however, both of these cases are errors in a
RESUME statement.
Traditionally, boolean values in INTERCAL programs
have been stored using #1 and #2 as the two logic levels. This is
because the easiest way to implement an if-like construct in
INTERCAL-72 is by NEXTING, then
NEXTING again, then RESUMING either by 1 or 2
according to an expression, and then if the expression evaluated to 1
FORGETTING the remaining NEXT stack entry. By the way, the
previous sentence also explained what the appropriate gerunds are for
NEXT, RESUME, and FORGET.
| INTERCAL-72 | C-INTERCAL | CLC-INTERCAL |
J-INTERCAL
|
|---|---|---|---|
| yes | all versions | all versions |
all versions
|
The NEXT stack is not the only stack available in an
INTERCAL program; each variable used in the program
also has its own stack, which holds values of the same type as the
variable. The STASH command pushes a variable's value onto
that variable's stack; RETRIEVE can be used in the same
way to pop the top element of a variable's stack to replace that
variable's value. The syntax is the same as most other
INTERCAL commands, with the word STASH
or RETRIEVE followed by the variable or variables to stash
or retrieve:
DO STASH .1 + ;2 DO RETRIEVE ,3
Note that it is possible to stash or retrieve multiple variables at
once, by listing their names separated by intersections
(+); it's even possible to stash or retrieve a variable
twice in the same statement.
It is not entirely clear how RETRIEVE interacts with
IGNORE in historical INTERCAL-72 compilers;
the three modern INTERCAL compilers all use
different rules for the interaction (and the C-INTERCAL
maintainers recommend that if anyone decides to write their own
compiler, they choose yet another different rule so that looking at the
interaction (the so-called `ignorret test') can be used as a method of
determining which compiler is running):
RETRIEVE simply allows a change to its value despite the
read-only status.
The appropriate gerunds for STASH and
RETRIEVE are STASHING and
RETRIEVING respectively.
| INTERCAL-72 | C-INTERCAL | CLC-INTERCAL |
J-INTERCAL
|
|---|---|---|---|
| yes | all versions | all versions |
all versions
|
Variables in INTERCAL can be either read-write or
read-only. At the start of a program, all variables are read-write, but
this status can be changed dynamically during execution of a program
using the IGNORE and REMEMBER statements
(whose gerunds are IGNORING and REMEMBERING
respectively). The syntax is the same as for STASH and
RETRIEVE: the command's name followed by an
intersection-separated list of variables. For instance:
DO IGNORE .4 DO REMEMBER ,4 + ;5
Using the IGNORE statement sets a variable to be read-only
(or does nothing if it's read-only already); REMEMBER sets
it to be read-write. Any attempt to assign to a read-only variable
silently fails. One place that this is used is in the system library;
instead of not assigning to a variable in certain control flow paths,
it instead sets it to be read-only so that subsequent assignments don't
change its value (and sets it to be read-write at the end, which
succeeds even if it was never set read-only in the first place); the
advantage of this is that it doesn't need to remember what flow path
it's on except in the variable's ignorance status.
The interaction between IGNORE and RETRIEVE
was never defined very clearly, and is in fact different in
C-INTERCAL, CLC-INTERCAL and
J-INTERCAL; for more details, see RETRIEVE.
| INTERCAL-72 | C-INTERCAL | CLC-INTERCAL |
J-INTERCAL
|
|---|---|---|---|
| yes | all versions | all versions |
all versions
|
The statement identifier of a statement determines whether it's in an
abstained or reinstated state at the start of a program; these states
determine whether the statement runs at all when it's encountered. It
is, however, possible to change this state dynamically during a
program's execution, and the statements to do this are rather
appropriately named ABSTAIN and REINSTATE.
There are two forms of each, one which takes a single line label (which
must be constant in most compilers, but can instead be an expression in
recent CLC-INTERCAL versions), and one which takes an
intersection-delimited list of gerunds. They look like this:
DO ABSTAIN FROM ABSTAINING + REINSTATING DO ABSTAIN FROM (10) DO REINSTATE CALCULATING DO REINSTATE (22)
(This also illustrates the gerunds used for these commands; note that
ABSTAINING from REINSTATING is generally a
bad idea!) The line referenced, or every command represented by any
gerund referenced, are reinstated or abstained as appropriate
(effectively changing the DO to DON'T (or PLEASE to PLEASE DON'T,
etc.), or vice versa). Using these forms of ABSTAIN and/or
REINSTATE won't abstain from a command that's already
abstained, or reinstate a command that's already reinstated.
There is a strange set of restrictions on ABSTAIN and
REINSTATE that has existed since INTERCAL-72;
historically such restrictions have not always been implemented, or
have not been implemented properly. They together define an unusual
interaction of ABSTAIN and GIVE UP (note, for
instance, that there isn't a gerund for GIVE UP). The
wording used in the INTERCAL-72 manual is:
[...] the statement DO ABSTAIN FROM GIVING UP is not accepted, even though DON'T GIVE UP is. [...] DO REINSTATE GIVING UP is invalid, and attempting to REINSTATE a GIVE UP statement by line label will have no effect. Note that this insures that DON'T GIVE UP will always be a "do-nothing" statement.
This restriction was not implemented at all in the only
CLC-INTERCAL version before 0.02 (i.e. version 0.01), or
in C-INTERCAL versions before 1.26. The restriction was
implemented in C-INTERCAL version 1.26 and
CLC-INTERCAL versions 0.02 and later as “GIVE
UP cannot be REINSTATED or ABSTAINED
FROM”; however, this is not strictly the same as the
definition used by INTERCAL-72 (C-INTERCAL
still uses this definition in CLC-INTERCAL compatibility
mode). The J-INTERCAL implementation of this restriction
is to make REINSTATING or ABSTAINING from a
line label that refers to a GIVE UP statement a
compile-time error, but this does not fit the INTERCAL-72
definition either. The definition adopted with version 0.27 and later
of C-INTERCAL, which is hopefully correct, is to allow
abstaining from a GIVE UP statement by line number but to
rule out the other three cases (reinstating by line number silently
fails, reinstating or abstaining by gerund is impossible because there
is no gerund).
As well as CLC-INTERCAL's extension to abstain/reinstate
by computed line number, there is also (since version 0.25) a
C-INTERCAL-specific extension to ABSTAIN,
also known as `computed abstain', but with a different syntax and
different semantics. It's written like an ordinary
ABSTAIN, but with an expression between the words
ABSTAIN and FROM, for instance:
DO ABSTAIN #1 FROM (1000) DO ABSTAIN .2 FROM WRITING IN
Unlike non-computed ABSTAIN, this form allows a command to
be abstained from even if it's already been abstained from; so if the
first example command is run and line (1000) is already abstained, it
becomes `double-abstained'. The number of times the statement is
abstained from is equal to the number of times it was already abstained
from, plus the expression (whereas with non-computed abstain, it ends
up abstained once if it wasn't abstained at all, and otherwise stays at
the same abstention status). Reinstating a statement always de-abstains
it exactly once; so double-abstaining from a statement, for instance,
means it needs to be reinstated twice before it will actually execute.
There are many uses for ABSTAIN (both the computed and
non-computed versions) and REINSTATE, especially when
interacting with ONCE and AGAIN (see ONCE and AGAIN); the computed version, in
particular, is a major part of a particular concise way to write
conditionals and certain kinds of loops. They also play an important
role in multithreaded programs.
The READ OUT and WRITE
IN commands are the output and input commands in
INTERCAL; they allow communication between the
program and its user. There was a numeric I/O mechanism implemented in
INTERCAL-72, and it (or trivial variants) have been
likewise implemented in all more modern variants. However, it had some
obvious deficiences (such as not being able to read its own output)
which meant that other methods of I/O were implemented in
C-INTERCAL and CLC-INTERCAL.
The syntax of READ OUT and WRITE IN is the
same in all cases: the name of the command followed by an
intersection-separated list of items; the form of each item, the
compiler you are using, and its command line arguments together
determine what sort of I/O is used, which can be different for
different elements in the list.
| INTERCAL-72 | C-INTERCAL | CLC-INTERCAL |
J-INTERCAL
|
|---|---|---|---|
| yes | all versions | see text |
all versions
|
INTERCAL-72 had its own versions of I/O commands; these
commands are available in all modern INTERCAL
compilers as well (but CLC-INTERCAL implements output
slightly differently). To distinguish INTERCAL-72 input
and output from the other more modern types of I/O, the READ
OUT and WRITE IN commands must take one of the
following values: a onespot or twospot variable, a single element of a
tail or hybrid array, or (in the case of READ OUT) a
constant, meaning that these are some examples of the possible forms:
READ OUT .1 READ OUT ;2 SUB .3:4 READ OUT #3 WRITE IN :4 WRITE IN ,5 SUB #6
The statements do what you would expect; READ OUT outputs
its argument to the user, and WRITE IN inputs a number
from the user and assigns it to the variable or array element
referenced. (If the variable, or the array that contains the array
element, happens to be read-only, the input or output still happens but
in the case of WRITE IN silently skips the assignment,
instead throwing away the input.) The formats used for input and output
are, however, different from each other and from the formats used by
most mainstream languages.
Input is achieved by writing a number in decimal, one digit at a time,
with each digit written out as a word; so to input the number 12345, a
user would have to type ONE TWO THREE FOUR FIVE as input
(if they were using English, the most portable choice of language). In
INTERCAL-72 only English is accepted as a language, but
other compilers accept other languages in addition.
C-INTERCAL from version 0.10 onwards accepts English,
Sanskrit, Basque, Tagalog, Classical Nahuatl, Georgian, and Kwakiutl;
also Volapük from version 0.11 onwards, and Latin from version 0.20
onwards. J-INTERCAL accepts the same languages, except
with Esperanto instead of Latin; from version 0.05 of
CLC-INTERCAL onwards, the same list of languages as
C-INTERCAL is supported (apart from Latin, which was added
in version 1.-94.-8), plus Scottish Gaelic.
The format that output can be read in is a modified form of Roman numerals, known as `butchered' Roman numerals. INTERCAL-72, C-INTERCAL and J-INTERCAL do this the same way; CLC-INTERCAL is somewhat different. The characters ‘I’, ‘V’, ‘X’, ‘L’, ‘C’, ‘D’, and ‘M’ mean 1, 5, 10, 50, 100, 500 and 1000 respectively, placing a lower-valued letter after a higher-valued letter adds them, and placing a lower-valued letter before a higher-valued letter subtracts it from the value; so ‘XI’ is 11 and ‘IX’ is 9, for instance. In INTERCAL-72, C-INTERCAL, and J-INTERCAL, a bar over a numeral multiplies its value by 1000, and writing a letter in lowercase multiplies its value by 1000000; however, CLC-INTERCAL uses lowercase to represent multiplication by 1000 and for multiplication by 1000000 writes a backslash before the relevant numeral.
| INTERCAL-72 | C-INTERCAL | CLC-INTERCAL |
J-INTERCAL
|
|---|---|---|---|
| no | version 0.07+ | version 0.05+ |
no
|
C-INTERCAL's method of character-based (rather than
numeric) input and output is known as the Turing Tape method; it is a
binary (character-set-agnostic) input/output mechanism. To specify that
C-INTERCAL-style I/O is being used, an array must be used
as the argument to READ OUT or WRITE IN; as
the syntax is the same as for CLC-INTERCAL's I/O,
command-line arguments and the capabilities of the version of the
compiler being used serve to distinguish the two mechanisms.
The character-based input writes as many characters into a tail or
hybrid array as will fit, one character in each element. The number
that's written into the array is not the character code, though, but
the difference between the character code and the previous character
code, modulo 256. (To be precise, the code is the new character minus
the previous character, or 256 minus (the previous character minus the
new character) if the previous character had a higher character code;
the 'previous character' is the previous character from the input, not
the previous character written into the array.) End-of-file causes 256
to be written into the array. The concept is that of a circular tape
containing all the characters, where the program measures how many
spaces it needs to move along the tape to reach the next character. The
'previous character' starts at 0, but is preserved throughout the
entire program, even from one WRITE IN to the next.
Character-based output uses a similar model, but conceptually the output device moves on the inside of the tape, rather than on the outside. Therefore, the character is that is actually output is the bit-reversal of the difference between the last character output before it was bit-reversed and the number found in the array (subtracting in that order, and adding 256 if the result is negative). (Rather than trying to parse the previous sentence, you may find it easier to look either at the source code to the compiler if you have it (the relevant part is binout in src/cesspool.c) or at some example C-INTERCAL programs that do text-based I/O.)
| INTERCAL-72 | C-INTERCAL | CLC-INTERCAL |
J-INTERCAL
|
|---|---|---|---|
| no | see text | all versions |
no
|
There are also two CLC-INTERCAL-specific I/O mechanisms. These are Baudot-based text I/O (which is also implemented from C-INTERCAL version 0.27 onwards), and CLC-INTERCAL generalised binary I/O (not implemented in C-INTERCAL).
Baudot text-based I/O is specified by using a tail array as an argument
to WRITE IN or READ OUT. (A tail array can
also be used to specify C-INTERCAL-style Turing Tape I/O.
In order to determine which is used: both C-INTERCAL and
CLC-INTERCAL use their own sort of I/O unless a
command-line argument instructs them to use the other.) In the case of
WRITE IN, one line of input is requested from the user
(C-INTERCAL requires this to be input in Latin-1, and will
then automatically convert it; CLC-INTERCAL gives the
option of various character sets for this input as command-line
options); the final newline is removed from this line, then it is
converted to extended Baudot and stored in the tail array specified
(causing an error if the array is too small). Because Baudot is only a
5-bit character set, each element is padded to 16 bits;
CLC-INTERCAL pads with zeros, C-INTERCAL pads
with random bits. Trying to input at end-of-file will act as if the
input were a blank line. READ OUT is the reverse; it
interprets the array as extended Baudot and converts it to an
appropriate character set (Latin-1 for C-INTERCAL, or
whatever was specified on the command line for
CLC-INTERCAL), which is output to the user, followed by a
newline. Note that the Baudot is often longer than the corresponding
character in other character sets due to the need to insert shift
codes; for information on the extended Baudot character set, Character Sets.
Generalised binary I/O is specified using a hybrid array as an argument
to WRITE IN or READ OUT. Input works by
reading in a number of bytes equal to the length of the array (without
trying to interpret them or translating them to a different character
set), prepending a byte with 172 to the start, padding each byte to 16
bits with random data, then replacing each pair of consecutive bytes
(that is, the first and second, the second and third, the third and
fourth, and so on) with (the first element selected from the second
element) mingled with (the complement of the first element selected
from the complement of the second element). Output is the exact
opposite of this process. End-of-file reads a 0, which is padded with
0s rather than random data; if a non-end-of-file 0 comes in from the
data, its padding will contain at least one 1. Any
all-bits-0-even-the-padding being read out will be skipped.
| INTERCAL-72 | C-INTERCAL | CLC-INTERCAL |
J-INTERCAL
|
|---|---|---|---|
| yes | all versions | all versions |
all versions
|
The GIVE UP command causes the program to end (or, in a
multithreaded program, causes the current thread to end). It is written
simply as GIVE UP. There is not much else to say about it,
except to mention that it is the only way to end the program without an
error unless the last line of the program is TRY AGAIN,
and that it has an unusual interaction with ABSTAIN; for
details of this, see ABSTAIN. (Going past the
last command in the program is an error.)
There is no gerund for GIVE UP; in particular,
GIVING UP is a syntax error.
| INTERCAL-72 | C-INTERCAL | CLC-INTERCAL |
J-INTERCAL
|
|---|---|---|---|
| no | version 0.25+ | no |
no
|
The TRY AGAIN command is a very simple command with many
limitations; its effect is to place the entire program in a loop. If it
exists, it must be the very last command in the program (it cannot even
be followed by syntax errors), and it causes execution of the program
to go back to the first command. If the TRY AGAIN command
is abstained or for some other reason doesn't execute when reached, it
exits the program without the error that would usually be caused by
going past the last line of code.
The gerund for TRY AGAIN is TRYING AGAIN.
| INTERCAL-72 | C-INTERCAL | CLC-INTERCAL |
J-INTERCAL
|
|---|---|---|---|
| no | see text | see text |
see text
|
The COME FROM statement (incidentally also invented in
1972, but not in connection with INTERCAL) is the
main control-flow command in CLC-INTERCAL (which
deprecates NEXT), and one of two main control flow
structures in other modern INTERCAL compilers. It
takes either a label or an expression as its argument; these forms are
noncomputed COME FROM and computed COME FROM.
Noncomputed COME FROM was implemented in version 0.5 of
C-INTERCAL, but did not conform to modern-day semantics
until version 0.7; it is available in every version of
CLC-INTERCAL and J-INTERCAL. Computed
COME FROM support is available in every version of
CLC-INTERCAL and in C-INTERCAL from version
0.25 onwards, but not in J-INTERCAL; the variant
NEXT FROM of COME FROM is available from
CLC-INTERCAL version 1.-94.-8 and C-INTERCAL
version 0.26 (both computed and noncomputed). C-INTERCAL
and CLC-INTERCAL also have a from-gerund form of
COME FROM and NEXT FROM, which was also
implemented from CLC-INTERCAL version 1.-94.-8 and
C-INTERCAL version 0.26.
The basic rule of COME FROM is that if a COME
FROM statement references another statement, whenever that
statement is reached, control flow will be transferred to the
COME FROM after that statement finishes executing.
(NEXT FROM is identical except that in addition to the
COME FROM behaviour, the location immediately after the
statement that was nexted from is saved on the NEXT stack, in much the
same way as if the statement being nexted from was itself a
NEXT.)
Here are examples of noncomputed, computed, and from-gerund COME
FROM:
DO COME FROM (10) DO COME FROM #2$'.1~#1' DO COME FROM COMING FROM
(The last example is an infinite loop. If it said DO NEXT FROM
NEXTING FROM, it would not be an infinite loop because the NEXT
stack would overflow and cause an error. This also establishes the
gerunds used for COME FROM and NEXT FROM.)
There are some things to be careful with involving COME
FROM and NEXT FROM. First, if the statement come
from or nexted from happens to be a NEXT, the
NEXT doesn't count as 'finishing executing' until the NEXT
stack entry created by the NEXT is RESUMEd
to. In particular, this means that if FORGET is used to
remove the entry, or a RESUME with a large argument
resumes a lower entry, the COME FROM doesn't steal
execution at all.
Second, you may be wondering what happens if two COME
FROMs or NEXT FROMs aim at the same line. In a
non-multithreaded program (whether a program is multithreaded or not is
determined by a compiler option for those compilers that support it),
this is an error; but it is only an error if the statement that they
both point to finishes running, and both COME FROMs or
NEXT FROMs try to execute as a result (they might not if,
for instance, one is abstained or has a double-oh-seven causing it not
to run some of the time). If both COME FROMs or NEXT
FROMs are noncomputed, however, a compiler can (but does not
have to) give a compile time error if two COME FROMs or
NEXT FROMs share a label, and so that situation should be
avoided in portable code. (If it is wanted, one solution that works for
C-INTERCAL and CLC-INTERCAL is to use
computed COME FROMs or NEXT FROMs with a
constant expression.)
| INTERCAL-72 | C-INTERCAL | CLC-INTERCAL |
J-INTERCAL
|
|---|---|---|---|
| yes | all versions | no |
all versions
|
INTERCAL has a system library, called ‘syslib’ (versions for bases other than 2 will have a numeric suffix on the name). It is included automatically at the end of your program by the compiler whenever your program refers to a line from (1000) to (1999) without defining any line in that range in the program. (Although it is not added automatically by the compiler in CLC-INTERCAL, it is trivial to concatenate a copy onto the end of the program; copies of the system library are available from many sources on the Internet, including a version in the example code that comes with C-INTERCAL.)
The intention of the system library is to provide a range of useful
capabilities, like multiplication, that can otherwise be hard to write
in INTERCAL. System library routines are used by
NEXTING to their line number (see NEXT), where they will make changes to certain variables
depending on certain other variables (depending on which routine is
called), and RESUME back to the original program. As the
system library is itself written in INTERCAL, there
are some restrictions that need to be obeyed for calls to it to be
guaranteed to work; none of the variables it uses (.1 to
.6 and :1 to :5) should be
read-only or overloaded (although the value of any variables that
aren't mentioned in the routine's description will be preserved by the
routine), and none of the lines in it should have their abstention
status changed by lines outside it (this can happen with blatant
infractions like DO ABSTAIN FROM (1500) or more subtle
problems like gerund-abstention) or have COME FROMs or
NEXT FROMs aiming at them.
The system library is currently available in all bases from 2 to 7 (see TriINTERCAL), but not every command is available in every base, and C-INTERCAL is the only one of the three compilers listed above that has the system library to ship with a version in bases other than 2. (This table was originally based on the INTERCAL-72 manual, but has had extra information added for bases other than 2.) Here, “overflow checked” means that #1 is assigned to .4 if there is not an overflow, and #2 is assigned to .4 if there is; “overflow captured” means that if there is overflow, the digit that overflowed is stored in the variable referenced. In all cases, division by 0 returns 0.
| Line | Description |
Bases
|
|---|---|---|
| (1000) | .3 <- .1 plus .2, error exit on overflow |
2, 3, 4, 5, 6, 7
|
| (1009) | .3 <- .1 plus .2, overflow checked |
2, 3, 4, 5, 6, 7
|
| (1010) | .3 <- .1 minus .2, no action on overflow |
2, 3, 4, 5, 6, 7
|
| (1020) | .1 <- .1 plus #1, no action on overflow |
2, 3, 4, 5, 6, 7
|
| (1030) | .3 <- .1 times .2, error exit on overflow |
2, 3, 4, 5, 6, 7
|
| (1039) | .3 <- .1 times .2, overflow checked |
2, 3, 4, 5, 6, 7
|
| (1040) | .3 <- .1 divided by .2 |
2, 3, 4, 5, 6, 7
|
| (1050) | .2 <- :1 divided by .1, error exit on overflow |
2, 3, 4, 5, 6, 7
|
| (1200) | .2 <- .1 times #2, overflow captured in .3 |
4, 6
|
| (1210) | .2 <- .1 divided by #2, one digit after the quartic or sextic point stored in .3 |
4, 6
|
| (1500) | :3 <- :1 plus :2, error exit on overflow |
2, 3, 4, 5, 6, 7
|
| (1509) | :3 <- :1 plus :2, overflow checked |
2, 3, 4, 5, 6, 7
|
| (1510) | :3 <- :1 minus :2, no action on overflow |
2, 3, 4, 5, 6, 7
|
| (1520) | :1 <- .1 concatenated with .2 |
2, 3, 4, 5, 6, 7
|
| (1530) | :1 <- .1 times .2 |
2, 3, 4, 5, 6, 7
|
| (1540) | :3 <- :1 times :2, error exit on overflow |
2, 3, 4, 5, 6, 7
|
| (1549) | :3 <- :1 times :2, overflow checked |
2, 3, 4, 5, 6, 7
|
| (1550) | :3 <- :1 divided by :2 |
2, 3, 4, 5, 6, 7
|
| (1700) | :2 <- :1 times #2, overflow captured in .1 |
4, 6
|
| (1710) | :2 <- :1 divided by #2, one digit after the quartic or sextic point stored in .1 |
4, 6
|
| (1720) | :2 <- :1 times the least significant digit of .1, overflow captured in .2 |
5, 7
|
| (1900) | .1 <- uniform random number from #0 to #65535 |
2, 3, 4, 5, 6, 7
|
| (1910) | .2 <- normal random number from #0 to .1, with standard deviation .1 divided by #12 |
2, 3, 4, 5, 6, 7
|
If you happen to be using base 2, and are either using the external call system (see External Calls) or are willing to use it, it is possible to use a version of the system library written in C for speed, rather than the default version (which is written in INTERCAL). To do this, use the command line options -eE (before the INTERCAL file), and syslibc (at the end of the command line).
| INTERCAL-72 | C-INTERCAL | CLC-INTERCAL |
J-INTERCAL
|
|---|---|---|---|
| no | version 0.7+ | version 1.-94.-8+ |
no
|
One extension to INTERCAL that is implemented by both C-INTERCAL and CLC-INTERCAL is known as TriINTERCAL, and extends INTERCAL to bases other than binary. Unlike ordinary INTERCAL programs, which have the extension ‘.i’, TriINTERCAL programs in bases from 3 to 7 (the only allowed bases) have extensions from ‘.3i’ to ‘.7i’ respectively.
The change of numeric base only affects expressions, and in particular the behaviour of operators, and the range of variables. (The onespot and twospot ranges become the highest number of trits or other digits in the base required that fit inside the binary ranges, so for instance, the maximum value of a onespot variable in ternary is 59048, or 3 to the power 10 minus 1.) Interleave/mingle is the simplest to explain; it alternates digits just as it alternated bits in binary. The other operators all change, as follows:
? and ^). (In Princeton
syntax, these are the bookworm or yen sign, and a spike
(|).) The two operators do the same thing in binary, but
differ in higher bases. (Nevertheless, it is an error to use a sharkfin
in binary, because it is a so-called `controlled unary operator', as
are the rest of the new operators defined in this section, which has a
lower limit on which base it is allowed in.) Instead of doing the
exclusive-or operation, the bits being combined are either subtracted
or added; if the result is out of range for the base being used, the
base is added or subtracted from the result until it is in range. (For
the subtraction, the bit that was less significant is subtracted from
the bit that was more significant in any given pair of bits, except for
the subtraction between the most and least significant bits, where the
most significant bit is subtracted from the least.)
The way to think of it is this: in base 2, an AND gives the result
0 if either argument is a 0, and otherwise a 1, and likewise, an OR
gives the result 1 if either argument is a 1, and otherwise a 0;
they could be said to favour 0 over 1 and 1 over 0 respectively. In
base 3, AND favours 0 over 2 over 1, OR favours 2 over 1 over 0,
and BUT favours 1 over 0 over 2. (The symbol for BUT is
@ (a `whirlpool', which is another name for the BUT
operation) in Atari syntax, and ? in Princeton
syntax.) The pattern continues: in base 4, AND favours 0 over 3
over 2 over 1, BUT favours 1 over 0 over 3 over 2, 2BUT (written
2@ or 2?) favours 2 over 1 over 0 over 3,
and OR favours 3 over 2 over 1 over 0. (This can be extended to
higher bases following the same pattern, introducing operators
3@ or 3?, etc., to favour 3, etc., when
neither AND (which always favours 0) nor OR (which favours the
highest digit in the base) are available.) All the whirlpool
operators are controlled unary operators, which are only legal when
both the base contains the favoured digit, and they aren't
redundant to AND nor OR.
Note that the base doesn't affect anything other than variable ranges and expressions; in particular, it doesn't affect the bit-reversal used by Turing Tape I/O. (The tape still has characters written on it in binary, even though the program uses a different base.)
The multithreading and
backtracking extensions to INTERCAL were originally
invented by Malcom Ryan, who implemented COME FROM-based
multithreading as a modified version of C-INTERCAL, known
as Threaded INTERCAL, but did not implement
backtracking. (The same functionality is implemented in
C-INTERCAL today, but with different code. Most likely,
this means that the original code was better.) He also invented the
original version of Backtracking INTERCAL, but did
not implement it; the only known implementation is the
C-INTERCAL one. A different version of multithreading,
using WHILE, was implemented as part of
CLC-INTERCAL (like all extensions first available in
CLC-INTERCAL, it is most likely due to Claudio Calvelli)
and then added to C-INTERCAL, although its implications
were not noticed for some time afterwards.
So nowadays, three freely-mixable threading-like extensions to INTERCAL exist, all of which are implemented in C-INTERCAL. (A fourth, Quantum INTERCAL, is implemented in CLC-INTERCAL but not C-INTERCAL, and so will not be discussed further here.) If you're wondering about the description of backtracking as a threading-like extension, it's implemented with much of the same code as multithreading in C-INTERCAL, because the INTERCAL version can be seen as roughly equivalent to multithreading where the threads run one after another rather than simultaneously. (This conceptualisation is probably more confusing than useful, though, and is also not strictly correct. The same could probably be said about INTERCAL as a whole, for that matter.)
| INTERCAL-72 | C-INTERCAL | CLC-INTERCAL |
J-INTERCAL
|
|---|---|---|---|
| no | version 0.25+ | version 0.05+ |
no
|
The original multithreading implementation worked by giving a new
meaning to what was previously an error condition. If in a
multithreaded program (a program is marked as multithreaded using
options to a compiler) two or more COME FROMs or
NEXT FROMs (or a mixture of the these) attempt to steal
control simultaneously, the original thread splits into multiple
threads, one for each of the commands trying to take control, and a
different command gains control of the program in each case.
From then on, all the threads run simultaneously. The only thing shared
between threads (apart from the environment in which they run) is the
abstained/reinstated status of each command; everything else is
separate. This means, for instance, that it's possible to change the
value of a variable in one thread, and it will not affect the
corresponding variable in other threads created this way. Likewise,
there is a separate NEXT stack in each thread; if both a COME
FROM and a NEXT FROM aim at the same line, for
instance, the NEXT FROM thread will end up with a NEXT
stack entry that isn't in the COME FROM thread, created by
the NEXT FROM itself. This is known as unwoven thread
creation; none of the threads created this way are `woven' with any of
the other threads created this way. (Whether threads are woven depends
on how they were created.) If the thread being split was itself woven
with other threads, exactly one of the resulting threads after the
split is woven with the threads that the original thread was woven to,
but the rest will not be woven to anything. (If that seems a somewhat
unusual rule: well, this is INTERCAL.)
In C-INTERCAL, there are other guarantees that can be made
about unwoven threads (that is, threads not woven to any other thread).
In particular, they can all be guaranteed to run at approximately the
same speed; to be more precise, the number of commands that have been
given the chance to execute in any given thread will not differ by more
than 2 from the number of commands that have been given the chance to
execute in any other thread that was created at the same time.
(However, COME FROMs and NEXT FROMs can make
this relationship less precise; it is unspecified (in the technical
sense that means the compiler can choose any option it likes and change
its mind on a whim without telling anyone) whether a COME
FROM or NEXT FROM aiming at the current command
counts towards the command total or not, thus causing the relationship
to become weaker the more of them have the chance to execute. In
versions of C-INTERCAL from 0.27 onwards, there is a third
guarantee; that if a COME FROM comes from itself, it will
actually give other threads at least some chance to run, at some speed,
by counting itself as a command every now and then; previously this
requirement didn't exist, meaning that a COME FROM could
block all threads if it aimed for itself due to the speed restrictions
and the fact that COME FROMs need not count towards the
total command count.) Also, all commands, including any
ONCE or AGAIN attached to the command, are
atomic; this means that it's impossible for another thread to conflict
with what the command is doing. (In a departure from the usual
INTERCAL status quo, these guarantees are somewhat
better than in most other languages that implement threading,
amusingly continuing to leave INTERCAL with the
status of being unlike any other mainstream language.)
The only way to communicate between unwoven threads is by changing the
abstention status of commands; this always affects all threads in the
program, whether woven or not. (The combination of ABSTAIN
and ONCE is one way to communicate atomically, due to the
atomic nature of ONCE.)
If there are at least two threads, the GIVE UP command
ends the current thread, rather than the current program.
| INTERCAL-72 | C-INTERCAL | CLC-INTERCAL |
J-INTERCAL
|
|---|---|---|---|
| no | version 0.27+ | version 0.05+ |
no
|
The WHILE command (which is not strictly speaking a
command, but more a sort of metacommand that joins commands) is a
second method of achieving multithreading. (In
CLC-INTERCAL, there are at least two other meanings for
WHILE, but only the one implemented in
C-INTERCAL is discussed here.) The syntax is somewhat
unusual, and consists of two commands separated by the
WHILE keyword, but sharing the statement identifier,
execution chance, and any ONCE/AGAIN keyword
that may be present. For instance:
(1) DO COME FROM ".2~.2"~#1 WHILE :1 <-
"'?.1$.2'~'"':1/.1$.2'~#0"$#65535'"$
"'"'&.1$.2'~'#0$#65535'"$#0'~#32767$#1"
(OK, maybe that's an unnecessarily complicated example, and maybe it
shouldn't have included the / operator which is part of
another INTERCAL extension (see Operand Overloading). Still, I thought that
maybe you'd want to see how addition can be implemented in
INTERCAL.)
A WHILE command starts two threads (the original thread
that ran that command and a new one), one of which runs the command to
the left of the WHILE and one of which runs the command to
the right. Any line number applies to the left-hand command, not the
WHILE as a whole, which is a metalanguage construct. NEXTING
FROM, ABSTAINING FROM or similar behaviour with
respect to the WHILE itself is impossible, although it's
certainly possible to abstain from either of its operands (and
abstaining from the left operand has much the same effect as abstaining
from the WHILE itself; the right-hand thread deliberately
takes a bit of time to get started just so that this behaviour
happens). The right-command thread starts just before the left command
is run (so NEXTING, etc., directly to the left command
will not start that loop in the first place); if that command finishes
(which may be almost immediately for something like a calculate
command, or take a long time for something like NEXT),
that thread loops and reruns that command as long as the left command
has not finished; COMING FROM that command, or a
NEXT/NEXT FROM from/aiming at that command,
doesn't count as finishing that command until it is
RESUMEd back to (if possible; if it's come from, that
command can never end and the right-hand loop will continue forever, or
until it GIVEs UP or the loop ends due to the
command ending later in another thread). A WHILE command
itself exists across all threads of a multithreaded program in a way;
for each left-hand command that ends (in any thread), the next time a
right-hand command of the same WHILE ends it will cause
the thread it's looping in to end, regardless of whether that thread
corresponds to the thread in which the left-hand command ended. (As
well as a right-hand command ending, there's also the possibility that
it never got started; there is a delay before the right-hand command
runs during which a left-hand command ending can prevent the right-hand
thread starting in the first place; this counts as the same sort of
event as terminating a right-hand loop, and can substitute for it
anywhere a right-hand command ending is mentioned.) There is one
exception, in that if two or more left-hand commands end in a space of
time in which no right-hand commands for that WHILE ends,
they together only cause one right-hand command to end. (What, did you
expect the logical and orthogonal behaviour?)
The two threads produced by a WHILE (the original thread
and a new copy of it) have more in common than ordinary
INTERCAL threads created by COME FROM;
ordinary threads share only ABSTAIN/REINSTATE
information, whereas the WHILE-produced threads count as
`woven' threads which also share variables and stashes. (They still
have separate instruction pointers, separate instruction pointer
stacks, such as the NEXT stack, and separate choicepoint lists.
Overloading information is shared, though.) Being woven is a
relationship between two or more threads, rather than an attribute of a
thread, although a thread can be referred to as being unwoven if it is
not woven to any other thread.
Ordinary multithreading cannot create woven threads. When threads are
created by multiple COME FROMs from an original thread,
which was woven with at least one other thread, one of the resulting
threads counts as the `original' thread and remains woven; the rest are
`new' threads which initially start out with the same data as the
original, but are not woven with anything. Backtracking in a thread
(see Backtracking) causes it to unweave
with any threads it may be woven with at the time (so the data in the
thread that backtracks is set back to the data it, and the threads it
was woven with at the time, had at the time of the MAYBE,
but the other threads continue with the same data as before). The only
way to cause three or more threads to become woven is with a new
WHILE inside one of the threads that is already woven,
which causes all the new threads to be woven together (the weaving
relationship is transitive).
| INTERCAL-72 | C-INTERCAL | CLC-INTERCAL |
J-INTERCAL
|
|---|---|---|---|
| no | version 0.25+ | no |
no
|
A somewhat unusual threading construct that's available is
backtracking. In case you haven't come across it before (the concept
exists in other languages but is implemented differently and usually in
a less general way), the basic idea is that instead of executing or not
executing a command, you can MAYBE execute a command. This
causes the command to be executed, but also creates a dormant thread in
which the command wasn't executed; at any time later, the program can
either decide that it liked the consequences of the command and
GO AHEAD and get rid of the dormant thread, or decide that
it didn't like the consquences of the command and GO BACK
to the dormant thread, discarding the current one. The dormant thread
is more commonly called a `choicepoint', that is, a point at which a
choice was made but a different choice can still be made, and is
generally not thought of as a thread at all by most programmers. (In
case you're wondering: dormant threads are always unwoven.)
To create a choicepoint,
the statement identifier MAYBE is used, rather than the
more usual DO or PLEASE. (Combination
statement identifiers are still allowed, but must be in the order
MAYBE PLEASE DO NOT with optionally some parts omitted, or
different versions of NOT used, or both.) Here's an
example:
MAYBE DON'T GIVE UP
When a command whose statement identifer contains MAYBE is
reached, it is executed or not executed as normal, but in addition a
choicepoint is created containing the program as it is at that time.
Only ABSTAIN and REINSTATE, which always
affect all threads in a program (even choicepoints), can alter the
values stored in the choicepoint; so in this way, a choicepoint is also
somewhat similar to the concept of a continuation in other languages.
The choicepoint is placed on a choicepoint stack, which is maintained
separately for each thread in much the same way that stashes and the
NEXT stack are.
The choicepoint does not
actually do anything immediately, but if the program doesn't like the
look of where it's ended up, or it decides to change its mind, or just
wants to try all the possibilities, it can call the GO
BACK command (which has no arguments, and is just the statement
identifier, optional execution chance, GO BACK, and
optional ONCE or AGAIN). This causes the
current thread to unweave from all other threads and then replace
itself with the thread created by the choicepoint on top of the
choicepoint stack. The difference is that this time, the abstention or
reinstatement status of the command that was modified with
MAYBE is temporarily reversed for determining whether it
runs or not (this reversal only lasts immediately after the GO
BACK, and does not affect uses of the command in other threads
or later in the same thread), so unless it has been
ABSTAINed or REINSTATEd in the meantime it
will run if and only if it wasn't run the first time. The choicepoint
stack's top entry is replaced by a `stale' choicepoint that definitely
isn't a thread; attempting to GO BACK to a stale
choicepoint instead causes the stale choicepoint to be deleted and the
program to continue executing. (This is what gives
INTERCAL's backtracking greater flexibility in some
ways than some other languages; to get backtracking without the stale
choicepoints having an effect, simply run COME FROM the
GO BACK as the previous statement.)
Note that, though, when a thread splits into separate threads (whether
woven or unwoven), the choicepoint stack doesn't split completely, but
remains joined at the old top of stack. The two choicepoint stacks can
add and remove items independently, but an attempt to GO
BACK to before the current thread split off from any other
threads that are still running instead causes the current thread to
end, although it will GO BACK as normal if all other
threads that split off from it or that it split off from since the top
choicepoint of the stack was created have ended since. This means that
it's possible to backtrack past a thread splitting and get the effect
of the thread unsplitting, as long as both resulting threads backtrack;
this is another way in which INTERCAL's backtracking
is more flexible than that of some other languages.
If, on the other hand, a
program decides that it likes where it is and doesn't need to GO
BACK, or it wants to GO BACK to a choicepoint lower
down the stack while skipping some of the ones nearer the top of the
stack, it can run the GO AHEAD command, which removes the
top choicepoint on the stack, whether it's a genuine choicepoint or
just a stale one.
Both GO AHEAD and GO BACK cause errors if an
attempt is made to use them when the choicepoint stack is empty.
| INTERCAL-72 | C-INTERCAL | CLC-INTERCAL |
J-INTERCAL
|
|---|---|---|---|
| no | version 0.26+ | version 0.05+ |
no
|
(Operand overloading in C-INTERCAL is nowhere near as advanced as it is in CLC-INTERCAL. This chapter only explains the partial implementation used by C-INTERCAL; for a full implementation, see CLC-INTERCAL and its documentation.)
Operand overloading is a method of using a onespot or twospot variable as a substitute for an expression. When a variable is overloaded to an expression (which could be another variable, or something more complex), any uses of that variable cause the expression to be substituted instead.
At the beginning of the program, all variables stand for themselves; so
.1 really does mean .1, for instance. The
meaning of a variable can be overloaded using the slat operator
(/), which is the same in both Princeton and Atari syntax:
it is a binary operator whose left argument must be a onespot or
twospot variable and whose right argument can be any expression. The
slat operator returns the true value of its left argument, but as a
side effect, changes the meaning of its left argument to be its right
argument. Here is an example:
DO .1 <- .2/'.3~.4'
The example causes .2's true value to be assigned to
.1 (unless of course .1 is read-only), but
also causes .2 from then on to actually mean
'.3~.4', except when it's the left operand of a slat
operator. So for instance, DO .1 <- .2 would actually
assign '.3~.4' to .1. Somewhat confusingly,
this also works in the other direction; DO .2 <- .1
would assign .1 to '.3~.4', which would have
the effect of changing the values of .3 and
.4 so that '.3~.4' had the correct value, or
throw an error if it couldn't manage this. (The general rule in this
case is that any variable or constant in the expression that overloads
the variable is at risk of being changed; this is known as a `reverse
assignment'. Code like DO .1 <- .1/#1 is entirely
capable of changing the value of #1, although to protect
new INTERCAL users C-INTERCAL will
refuse to carry out operations that change the value of constants
unless a command-line switch (see -v) is used
to give it permission. In C-INTERCAL, changing the value
of a constant only changes meshes with that value, but in
CLC-INTERCAL it can also change non-mesh uses of that
constant, so doing so is not portable anyway.)
When multiple overloading rules are in effect, they are all applied;
overloading .1 to '.2~.3' and .2
to '.3$.4' will cause .1 to refer to
''.3$.4'~.3'. However, this expansion stops if this would
cause a loop; to be precise, overloading is not expanded if the
expansion is nested within the same expansion at a higher level (so
.1/.2 and .2/.1 together cause
.1 to expand to .2, which expands to
.1, which cannot expand any further). In
C-INTERCAL, the expression on the right hand side of a
slat is not evaluated and not expanded by operand overloading.
STASHING a variable causes its overloading information to
be stashed too; RETRIEVING it causes its overload rule to
also be retrieved from the stash (or any overload rule on the variable
to be removed if there wasn't one when the variable was stashed).
Overloading a onespot variable to a twospot variable or vice versa is possible, but the results are unlikely to be predictable, especially if a onespot variable is used to handle a twospot value. Possible outcomes include truncating the value down to the right bitwidth, throwing an error if a value outside the onespot range is used, and even temporarily handling the entire twospot value as long as it doesn't end up eventually being assigned a value greater than twospot.
Note that reverse assignments can cause unpredictable behaviour if an
attempt is made to reverse-assign the same variable twice in the same
expression. In particular, sequences of commands like DO .1 <-
.2/'.3$.3' DO .2 <- #6 are liable to succeed assigning
garbage to .3 rather than failing as they ought to do, and
likewise any situation where a variable is reverse-assigned twice in
the same expression may assign garbage to it. This behaviour is seen as
unsatisfactory, though, and plans exist to improve it for future
versions.
| INTERCAL-72 | C-INTERCAL | CLC-INTERCAL |
J-INTERCAL
|
|---|---|---|---|
| no | version 0.26+ | no |
no
|
PIC-INTERCAL is a simplified version of INTERCAL designed especially for embedded systems, designed to minimise code and data usage by INTERCAL programs so that they can fit on devices whose memory is measured in bytes rather than megabytes. (It is named after the first microcontroller for which code was successfully generated, and which influenced the choices of commands, the PIC16F628 manufactured by Microchip, and is most likely to be portable to other microcontrollers in the same range.) C-INTERCAL only compilers as far as C code when producing PIC-INTERCAL; it is up to the user to find the appropriate cross-compiler to translate this C into the relevant dialect of machine code. (Two header files in the distribution, src/pick1.h and src/pick2.h, don't have any affect on the compiler but are referenced by the generated code, and the intent is for the user to change them to suit the behaviour of the PIC compiler used, because these are not as standardised as C compilers for everyday systems.)
There are several restrictions on PIC-INTERCAL programs:
ABSTAIN and REINSTATE still work, but
cannot be computed ABSTAINs, and will not necessarily
work when used to affect the system library or calls to it.
READ OUT and WRITE IN don't work. (See
below for a replacement.)
COME FROM and NEXT FROM must aim at a
label, not an expression or gerund.
In order to provide
I/O capabilities, a new command PIN is available. It
controls up to 16 I/O pins on the PIC or other embedded system; an I/O
pin is capable of receiving or sending voltages to an electrical or
electronic circuit. This explanation assumes that the device being
controlled is a PIC16F628A, and therefore has its pins in two blocks of
8 named ‘PORTA’ and
‘PORTB’; for other
microcontrollers, adapting the code in src/pick1.h is likely to be necessary to tell the
compiler how to control the I/O pins, and the way in which this done
will affect which I/O pins it is that the program will end up being
able to communicate with.
The PIN command takes one twospot variable as its
argument, like this:
DO PIN :2
The twospot variable is conceptually divided into 4 blocks of 8 bits.
The highest two blocks control the directions of the pins in
PORTB (most significant block) and PORTA
(second most significant block); a 1 on any bit means that the
corresponding I/O pin should be set to send data, and a 0 means that it
should be set to receive data. The lower two blocks control the values
on the pins that are sending (and are ignored for receiving pins); the
second least significant block controls PORTB and the
least significant block controls PORTA, with a 1 causing
the program to set the output voltage to that of the microcontroller's
negative voltage supply rail, and a 0 causing the program to set the
output voltage to that of the microcontroller's positive voltage supply
rail. (These voltages may vary on other systems; consult your system's
datasheet and the changes you made to the header files.) After setting
the pins, the PIN command then reads them as part of the
same operation, this time setting the values of the lower blocks that
are receiving, rather than setting the pins from the lower blocks that
are sending. However, 1 and 0 bits on all bits of the twospot variable
have the opposite meaning when doing this, so that 1 means
receiving/positive voltage rail and 0 means sending/negative voltage
rail. There is no way to input without output, or vice versa, but it's
trivial to just send the same output again (which has no effect,
because the voltage on sending pins is maintained at the same level
until it is changed), or to ignore the input received.
| INTERCAL-72 | C-INTERCAL | CLC-INTERCAL |
J-INTERCAL
|
|---|---|---|---|
| no | version 0.28+ | see text |
no
|
The CREATE command allows the creation of new syntax at
runtime. CLC-INTERCAL has had such a command since
1.-94.-8, but its syntax is completely different and incompatible with
the C-INTERCAL version, and so is not documented here (see
the CLC-INTERCAL documentation for more details). The
C-INTERCAL version is only defined if the -a
option is used on the command line (and a runtime error E000
otherwise), because it forces the operand overloading code to be
introduced and so slows down every variable access in the program.
The syntax of the CREATE command is to write
CREATE, then a line label, then anything. OK, well not
quite anything; you're restricted to syntax that is supported by the
`just-in-case' compiler that runs on comments at compile time just in
case they gain a meaning later (see below). The anything provides an
example statement to CREATE; statements which look the
same (but may differ in details) are created. Typical syntax for a
CREATE statement would therefore look something like this:
DO CREATE (5) SWITCH .1 WITH .2
There is also computed CREATE, working identically to
ordinary CREATE except that the line number is taken from
an expression and the created command must start with a letter (to
avoid an ambiguity if the expression giving the line label happens to
be an array reference), with a syntax like this:
DO CREATE .5 SWITCH .1 WITH .2
Here, a new SWITCH WITH statement (there is no such
statement in INTERCAL normally) is being created.
This command makes it possible to do this:
DO SWITCH .3 WITH .4
Normally that line would be an error (E000) due to being unrecognised,
but having been CREATEd, it's now a real statement. (The
gerund to affect created statements is COMMENT, just like
before they were created; the gerund to affect CREATE
itself is CREATION (CREATING is also allowed,
but not as elegant).) When the created statement is encountered, it
NEXTs to line (5), the line number specified in the
CREATE statement. In order for the code there to be able
to affect the variables mentioned in the statement, the variables
:1601 (for the first variable or expression mentioned),
:1602 (for the second variable or expression mentioned),
and so on, are STASHed and then overloaded to the
respective expressions or variables mentioned in the created command;
so :1601 has been overloaded to mean .3 and
:1602 has been overloaded to mean .4 at this
point. Then, the code at (5) runs; if it returns via a RESUME
#1, :1601 and :1602 will be
RETRIEVEd automatically and the program will continue from
after the created statement. (If you do not resume to that point, say
if you're creating a flow control statement, you'll have to deal with
the stashes for the 1600-range variables yourself.)
So what syntax is available in created statements? All the capital
letters except ‘V’
(which is an operator in INTERCAL) are available and
can be used freely and as many times as desired; they match themselves
literally. However, they are not allowed to spell an
INTERCAL keyword at any point (so watch out for
DO and FROM, for instance). Whitespace is
allowed, but is ignored (both in the CREATE template
statement, and in the code being created; so DO SW ITCH :8 WITH
:50 will also have been created). Then, there are three groups
of matchable data: scalar variables (onespot or twospot variables, as
used in the examples above) match other scalar variables, array
elements (like ,4 SUB '.5~.6') match other array elements,
and other expressions match other other expressions. Two matchable data
may not appear consecutively in a created command, but must be
separated by at least one capital letter (to prevent
array-subscript-related ambiguities; remember that the just-in-case
compiler has to compile these statements at compile time without
knowing what they are). The actual expressions used in the
CREATE statement don't matter; they're just examples for
the runtime to match against.
It is also possible (from C-INTERCAL version 0.29 onwards) to create new operators. Such operators are always binary operators (that is, they take two arguments and parse like mingle or select), and always return 32-bit results. There are three types of legal names for such operators, all of which are treated equivalently: lowercase letters, punctuation marks otherwise unused in INTERCAL, and overstrikes consisting of a character, a backspace, and another character (apart from overstrikes already used for built-in INTERCAL operators). The syntax for creating an operator looks like one of these:
DO CREATE (5) x DO CREATE .5 =
The arguments to the operator will be overloaded onto :1601 and :1602
(which are, like with CREATEd statements, stashed before
the overloading happens), and the return value is read from :1603
(which is stashed, then overloaded to itself). All these three
variables are retrieved again after the operator finishes evaluating.
Note that it is a very unwise idea to use a CREATEd
operator in the expression for a computed COME FROM or
NEXT FROM, because this always leads to an infinite
regress; whenever any line label is reached (including the line label
that the CREATE statement pointed at), the expression
needs to be evaluated in order to determine whether to COME
FROM that point, which in turn involves evaluating lines which
have labels.
Some other points: a newer CREATE statement supercedes an
older CREATE statement if they give equivalent templates,
multiple CREATE statements may aim at the same line (this
is the recommended technique for creating a statement that can handle
expressions even if they're array elements or variables; you do this by
specifying multiple templates in multiple CREATE
statements), and strange things happen if a twospot variable in the
1600-range is used as an argument to a created statement itself
(because of the stash/retrieve, such a variable can usually be read,
but may not always be able to be written without the data being lost).
| INTERCAL-72 | C-INTERCAL | CLC-INTERCAL |
J-INTERCAL
|
|---|---|---|---|
| no | version 0.28+ | no |
no
|
C-INTERCAL has a feature allowing INTERCAL and non-INTERCAL code to be mixed. This is achieved by causing the non-INTERCAL programs to participate in the INTERCAL line-numbering model. The same feature allows expansion libraries to be linked into the code.
To create a combined program containing INTERCAL and non-INTERCAL code, use ick as the compiler as normal, but specify both the INTERCAL and non-INTERCAL source files on the command line, and use the -e command-line option. ick will invoke other compilers as necessary, after modifying the source files accordingly. At present, external calls are only supported to and from C.
In each case, it will be the INTERCAL program that
is invoked first. (This means that it is impossible to link together
more than one INTERCAL program, but you probably
don't want to, because concatenating the programs is likely to have a
similar effect.) You can get the INTERCAL program to
NEXT to the non-INTERCAL program
immediately, or the non-INTERCAL program to
COME FROM or NEXT FROM the
INTERCAL program immediately, to obtain the effect
of running the non-INTERCAL program first.
Note that external calls are incompatible with PIC-INTERCAL and with multithreading; note also that you must use gcc as your compiler, and GNU cpp and ld, for them to work in the current version of C-INTERCAL.
| INTERCAL-72 | C-INTERCAL | CLC-INTERCAL |
J-INTERCAL
|
|---|---|---|---|
| no | version 0.28+ | no |
no
|
Linking C and INTERCAL programs is achieved by
placing various constructs into the C programs that are equivalent to
various INTERCAL constructs. It is possible to
simulate a line with a label and a dummy command (which serves as a
COME FROM suckpoint and NEXT target), a
command with a line label, NEXT, RESUME, and
FORGET, and COME FROM and NEXT
FROM. Onespot and twospot variables are accessible from inside
the C program, where they can be read and written; however, the
INTERCAL program cannot access any variables inside
the C program that weren't part of the INTERCAL
program originally.
To prevent various logical impossibilities, there are restrictions on where these can be used and what preparation is needed before they are used. Also, the semantics are not always exactly what you might expect for technical reasons.
It should be observed that the INTERCAL link
intrudes on the user namespace. To prevent possible namespace clashes,
no identifiers starting with ick_ or ICK_
should be used anywhere in the linked C program for any reason, except
where specified in this manual.
For a C program to be connected to an INTERCAL program, it needs to be marked with the correct header file, and needs to have functions marked for communication with the INTERCAL program.
#include <ick_ec.h>
ICK_EC_FUNC_START
ICK_EC_FUNC_END
ick_linelabel, ick_comefrom, and
ick_nextfrom) make it possible to jump from an
INTERCAL program to a C program. Because C doesn't
allow jumping into the middle of a function, there has to be some way
to create a block of code which can be jumped into. This is
what these two macros achieve.
This declaration and definition:
ICK_EC_FUNC_START(identifier)
{
/* code goes here */
}
ICK_EC_FUNC_END
is equivalent to this:
void identifier(void)
{
/* code goes here */
}
except that it is possible to jump from an
INTERCAL program into the declared and defined
program. (If you need to write a prototype for the function early,
void identifier(void); is perfectly acceptable, but an
early prototype is not required unless you call the function from
earlier within the C code.) Of course, you can substitute any
identifier that's legal as a function name for
identifier (as long as it doesn't start with
ick_ or ICK_). The resulting function is
a function (for instance, you can take its address or call it in
the usual ways); the only differences are that it can be jumped
into from INTERCAL code and that it is
constrained to take no arguments and return no data. (It can still
access global and INTERCAL variables.) If the
function is jumped into from INTERCAL code, but
then control flow reaches the end of the function, or the function
return;s but was not called from C, the resulting
behaviour is undefined; C-INTERCAL will attempt to
continue by some means at that point, but may fail. If a function
is unsure whether it gained control from C or from INTERCAL code,
it may use ick_return_or_resume (described below).
Because you are not allowed to declare two C functions with the
same name (even in different modules), all functions declared with
ICK_EC_FUNC_START must have unique names across the
entire compilation.
It is sometimes necessary for a
C program to do its own initialisation before the INTERCAL program
starts running. To do so, it can use the ick_startup macro
inside a function declared with ICK_EC_FUNC_START; the
syntax is ick_startup(block), where the argument is an
expression, statement, or compound statement to run. The argument
itself must not contain any ick_-prefixed macros or functions except
possibly ick_create, may have side effects, and must fit the C
preprocessor's idea of what a macro argument should look like (it's
more used to parsing expressions than blocks; the general rule is to
avoid commas except when they're directly or indirectly inside
parentheses or strings).
A
line label is something that can be NEXTed to and
COME FROM. Unlike an INTERCAL line
label, it does not label a statement, and therefore attempts to
ABSTAIN or REINSTATE it may be errors, or may
be ignored (it's unspecified which, which means that either may happen
for any or no reason, but exactly one will happen in any given case,
although the choice might not be consistent).
The macro ick_linelabel(expression); may appear anywhere a
compound statement would normally be able to appear. (That is, it looks
like a function call being used as a standalone expression, but in fact
the places where it can appear are more limited.) In contrast to
ordinary line labels, an expression can be used rather than just a
constant; however, the behaviour is undefined if the expression has
side-effects. Upon encountering the line label, any COME
FROMs or NEXT FROMs aiming at the line label
(including ick_comefroms and ick_nextfroms)
will steal control from the program; RESUMING after a
NEXT FROM will work, but suffers from the same caveats as
setjmp/longjmp do (any auto variables that change their value between
the NEXT FROM and RESUME will have their
value clobbered (i.e. their value is no longer reliable and should not
be accessed)). Note that the INTERCAL variables are
immune to this problem. You can also avoid the problem by marking
variables as volatile in the C program.
It is possible to NEXT or ick_next to a
ick_linelabel, which has the same effect as saving the
NEXT stack, calling the function containing the
ick_linelabel and then immediately doing a C
goto to an imaginary label preceding it. Due to this
possibility, an ick_linelabel is only allowed within a
function defined with ICK_EC_FUNC_START.
In INTERCAL programs, labels don't stand on their
own, but instead label a statement. The difference between a standalone
line label and a line label that labels a statement is that COME
FROMs will come from the label itself (which is before
the next statement) when aiming at a standalone line label, but the
end of the statement when aiming at a labeled statement. To
achieve the same effect in C, the macro ick_labeledblock
is available; it can be used as
ick_labeledblock(expression,expression) or
ick_labeledblock(expression,statement); the first argument
is the label, and the second argument is an expression or statement to
label (if an expression is labeled, it will be converted to a statement
that evaluates it for its side effects and discards the result). It is
even permitted to label a block statement in this way. Note, however,
that you have to contend with the C preprocessor's ideas of where macro
arguments begin and end when doing this. Other than the position of the
COME FROM target created by the label, this behaves the
same way as ick_linelabel (so for instance, computed line
labels are allowed, but the expression that computes them must not have
side effects, and it is only allowed within a function defined with
ICK_EC_FUNC_START).
The ick_comefrom and ick_nextfrom macros are,
like the other INTERCAL flow control macros (as
opposed to functions), only allowed within a function defined with
ICK_EC_FUNC_START. They act almost exactly like the
INTERCAL statements of the same name (although note
that C statements cannot be ABSTAINed FROM
even if they act the same way as INTERCAL
statements); they are written as ick_comefrom(expression);
and ick_nextfrom(expression); respectively (note that they
must be called as statements, and cannot be used as part of an
expression). Whenever a standalone line label is encountered whose
expression evaluates to the same number as the expression inside the
ick_comefrom or ick_nextfrom, and that number
is at most 65535, then control will be transferred to the
ick_comefrom or ick_nextfrom, leaving a
NEXT stack entry behind in the case of
ick_nextfrom; likewise, if the end of a labeled statement,
expression or block is reached and the label has the right number. Some
caveats: the expression need not be constant, but must not have side
effects, must not be negative, and must fit into the range of an
unsigned long in the C program (and the statement will do
nothing if the expression evaluates to a value larger than 65535). In
keeping with the best C traditions, these caveats are not checked, but
instead result in undefined behaviour if breached.
There are also versions
ick_comefromif and ick_nextfromif, which take
a second parameter, which is a condition that specifies whether control
is actually stolen from the target. The condition may have side
effects, and is only run when the line numbers match; it should return
0 or NULL to leave control flow alone, or nonzero to steal control, and
should be either an integral type or a pointer type. Although side
effects are allowed, the condition must not look at or alter
auto or register variables in the enclosing
function, not even if they are also marked volatile.
(Global and static variables are fine, though.)
ick_next is a macro that
acts like the INTERCAL statement NEXT.
Contrary to the other INTERCAL-like macros, it can
be used in any function regardless of whether it was defined with
ICK_EC_FUNC_START; however, it must still be used as a
statement by itself, and a call to it looks like
ick_next(expression);. The expression is the label to
NEXT to, and works under the same rules as the expressions
for ick_comefrom; it need not be constant (unlike in
C-INTERCAL!), but must not have side effects, must not be
negative, must fit into the range of an unsigned long, and is ignored
if it is over 65535. If there happen to be multiple labels with the
correct value at the time, the compiler will NEXT to one
of them. Bear in mind that there is a limit of 80 entries to the
NEXT stack, and that this limit is enforced.
If the resulting NEXT stack entry is RESUMEd
to, the program will continue after the ick_next as if via
setjmp, with all the usual restrictions that that entails;
if the resulting NEXT stack entry is forgotten, then the
ick_next call will never return. (Notice the 'as if via
setjmp' condition allows you to preserve the vales of auto
and alloca-allocated storage as long as its value has not
changed since the ick_next was called, which is a
significantly more lenient condition than that normally imposed on such
variables (see External Calls and
auto).
ick_resume is a macro,
but there are few restrictions on its use; it is permitted to use it
inside an expression (but it returns void, making this not particularly
useful), and acts like a function which takes an unsigned short
argument, returns void, and has a prototype (but you cannot take its
address; if you need to be able to do that, write a wrapper function
for it). It can be used within any function regardless of how it was
declared, and never returns; instead, it pops the specified number of
NEXT stack entries and resumes execution at the last one
popped, just as the INTERCAL statement does. This
causes the same errors as the INTERCAL statement if
the number of entries popped is zero or larger than the
NEXT stack.
There is also a macro
ick_return_or_resume();; it can only be used inside a
function defined with ICK_EC_FUNC_START, and is equivalent
to return; if the function was called from C, or
ick_resume(1); if the function was called from
INTERCAL. It's therefore a safe way to return from
such a C function if you don't know how control reached it in the first
place.
The ick_forget macro
removes NEXT stack entries, and the corresponding C stack
entries. It must be called as a statement by itself, and its invocation
looks like this: ick_forget(expr);, where the expression
is the number of NEXT stack entries to forget (all of them
will be forgotten if the number is higher than the number of entries).
The expression will be casted to an unsigned short.
ick_forget can only be used inside a function declared
with ICK_EC_FUNC_START. As it is removing stack entries
both in INTERCAL and in C, it will clobber the value
of all auto variables created since the highest remaining
NEXT stack entry came into being (or since the start of
the program, if the NEXT stack is emptied by the command)
and also deallocate all alloca storage allocated since
then. It also causes the return address of the current function to
become undefined, so that function must not return; control may leave
it via RESUME, or via COME FROM, or via
NEXT or NEXT FROM followed by the relevant
NEXT stack entry being forgotten (the function is still
'running' but suspended while the NEXT stack entry still
exists). (Note that these restrictions are stronger than those on
RESUME; this is because RESUME preserves most
of the stack, but FORGET destroys parts of the stack and
therefore cannot avoid destroying the data stored there. It could be
much worse; a previous (never released) version of the code didn't
remove those parts of the stack in many circumstances, leading to a
stack leak that caused programs to segfault after a while.)
This class of four functions make it possible to get and set INTERCAL scalar variables from C code. Their prototypes are as follows:
uint16_t ick_getonespot(unsigned short varnumber); void ick_setonespot(unsigned short varnumber, uint16_t newvalue); uint32_t ick_gettwospot(unsigned short varnumber); void ick_settwospot(unsigned short varnumber, uint32_t newvalue);
The program will error out with a fatal error (see E200) if the variable you request is mentioned nowhere in
the INTERCAL program; if you attempt to set an
IGNOREd variable, the attempt will silently fail (just as
if you assigned to it in an INTERCAL program). The
get functions are safe to use in a computed line label, so you can use
them to produce computed line labels that depend on
INTERCAL variables. (uint16_t and
uint32_t are standard C data types; if your system doesn't
provide them, get better system header files.)
If you care about speed, note that .1 is the fastest variable of all to access, and otherwise variables first mentioned near the top of the INTERCAL program will be faster to access than variables mentioned lower down.
The ick_create function
(prototype: void ick_create(char*, unsigned long)) allows
the external calls system to be used to create new
INTERCAL syntax; to do this, you give a `signature'
representing the syntax you want to define and a line number to the
function (which are its two arguments, respectively). The signature
defines the syntax that you are defining; whenever that syntax is
encountered within the INTERCAL program, it will
NEXT to the line number you specify, which can do various
clever things and then RESUME back to the
INTERCAL program (or if you're defining a
flow-control operation, you might want to leave the NEXT
stack entry there and do other things). However, note that the
overloading of :1601, etc., will still take place as in
the INTERCAL version of CREATE if the
-a option is used (see
-a), so care is needed when writing flow
control statements that they work both with and without the option and
don't cause STASH leaks (which means no
FORGETting the relevant NEXT stack entry, and
no looking at 1600-range variables). This allows the external calls
system to define whole new INTERCAL commands, with
the same power as any other programming language.
There are various restrictions on what syntax you can
CREATE with this method, which are best explained by an
explanation of the relevant C-INTERCAL compiler internals.
When an INTERCAL program is compiled by
C-INTERCAL, any unrecognised statements it comes across
are compiled by a `just-in-case' compiler that attempts to compile them
anyway with no knowledge of their syntax, just in case the syntax
becomes defined later. (E000 (see E000) will be
thrown when such statements are encountered at runtime, unless the
syntax has been CREATEd since to give a statement a
meaning.) For the just-in-case compiler to run, the resulting statement
must be completely unrecognised; this means that it may contain no
keywords (not even a sequence of letters that forms a keyword, such as
FROM or DO), it must consist only of variable
names, expressions, and capital letters other than
‘V’ (because
‘V’ is a unary
operator, so otherwise there would be ambiguity), and in which any two
variable names or expressions are separated by at least one capital
letter. The compiler will produce a `signature' for the unknown command
that can be defined.
A signature consists of a
sequence of characters (and is represented as a null-terminated string;
the runtime makes a shallow copy of the string and keeps it until the
end of the program, so arrangements must be made to ensure that the
storage in which the string is allocated stays around that long, but
this opens up interesting possibilities in which the signature that was
actually CREATEd can be modified retroactively);
whitespace is not allowed in a signature. Capital letters can be used
(apart from ‘V’),
and match the same capital letters literally in the
INTERCAL syntax being created; also available are
the special characters ‘.,;~’, which match respectively a scalar
variable (a onespot or twospot variable such as :1), an
array variable (such as ;2), an array element (such as
,3 SUB #4 #5), and an expression that isn't a variable
name and isn't an array element (such as .4$.5). If you
want to be able to match other things (say, to be able to match all
expressions), you will need to submit multiple signatures using
multiple calls to ick_create; maybe you could write a
library to do that automatically.
CREATEd operators also have signatures, but of quite a
different form. The signature for a single-character operator is a
lowercase u, followed by its character code in hexadecimal (no leading
zeros, and in lowercase); the signature for an overstrike is a
lowercase o, followed by the lower relevant character code in
hexadecimal, followed by a lowercase x, followed by the higher relevant
character code in hexadecimal.
The routine that is NEXTed to will presumably want to be
able to see what in the INTERCAL program was matched
by the signature, so a range of function-like macros is provided to
access that. They must be run from within the invocation of the
function which was NEXTed into by the created syntax (see
External Calls and auto for when
a function invocation ends, which could be sooner than you think when
the C-INTERCAL external calls system is used), and are
undefined behaviour when that invocation did not gain control from a
CREATEd statement. Here are their effective prototypes:
int ick_c_width(int); int ick_c_isarray(int); unsigned short ick_c_varnumber(int); uint32_t ick_c_value(int); /* These require -a to work */ uint32_t ick_c_getvalue(int); void ick_c_setvalue(int, uint32_t);
The first argument to all these macros is the position of the match in the signature (0 for the first non-capital-letter match in the signature, 1 for the second, and so on until no more items are left in the signature to match); specifying a position that isn't in the signature is undefined behaviour.
ick_c_width returns the data type, as a width in bits, of
the expression (or the width in bits of an element of the passed in
array), and ick_c_isarray returns 1 if the argument was an
array variable or 0 if it was an expression (array elements and scalar
variables are expressions). ick_c_varnumber returns the
variable's number (for instance 123 for .123), or 0 if the
corresponding argument was not a variable; in the cases where the
argument was a variable, these three functions together provide enough
information to figure out which variable (which is useful if you're
writing an extension which takes a variable name as an argument).
ick_c_value returns the value of the corresponding
expression at the time the CREATEd command was called;
ick_c_getvalue is almost equivalent, but only works if the
-a option (see -a) was used during compilation, and returns the value
of the corresponding expression now. (The uint32_t return type is large
enough to hold either a onespot or twospot value, and will be
zero-extended if the corresponding expression had onespot type.)
ick_c_setvalue also depends on -a, and will assign to the corresponding
expression (be careful not to provide a value that is too large for
it!). In the case that the corresponding expression is not a variable,
this will attempt to perform a reverse assignment to the expression,
and can produce ordinary INTERCAL errors if it
fails. It is not possible to redimension an array this way, as this is
assignment, not a calculate operation.
Because the external calls
system merges the INTERCAL NEXT stack
with the C return value and data storage stack (note for pedants: the C
standards nowhere mandate the existence of such a stack, or even
mention one, but the restrictions stated in them imply that
implementations have to act as if such a stack existed, because of the
way the scoping rules and recursion work), the external calls system
therefore has severe effects on data that happens to be stored there.
(In INTERCAL terms, imagine what would happen if
data could be stored on the NEXT stack; if C used the more
sensible system of having a STASH for each variable, these
problems would never occur in the first place, instead causing an
entirely different set of problems.) Similar considerations apply to
the common nonstandard C extension alloca, which
dynamically alters the size of the stack; also, in what goes below,
register variables should be considered to be
auto, because the compiler may choose to allocate them on
the stack. Theoretical considerations would lead one to conclude that
variable-length arrays should obey most of the same restrictions; in
practice, though, it's unwise to attempt to mix those with
INTERCAL code at all, except by separating them into
separate functions which aren't flagged with
ICK_EC_FUNC_START and use no ick_-prefixed
identifiers, even indirectly. (They may cause a compile to fail
completely because they don't mix well with goto.)
In the description below, INTERCAL commands should be taken to include the equivalent C macros.
NEXT/NEXT FROM paired with
RESUME have the least effect, and the most obvious effect,
on auto variables in the function that was
NEXTed from, which is the same effect that the standard C
function longjmp has. That is, alloca storage
stays intact, and auto variables have their values
`clobbered' (that is, their value is no longer reliable and should not
be used) if they changed since the corresponding NEXT and
are not marked as volatile. (This is a very easy
restriction to get around, because changing the values of such
variables is quite difficult without using statically-allocated
pointers to point to them (a dubious practice in any case), and
volatile is trivial to add to the declaration.)
COME FROM has more restrictions; it deallocates all
alloca storage in the function that was COME
FROM, and functions that called it or that called functions that
called it, etc., using C calls (as opposed to NEXT), and
those invocations of the functions will cease to exist (thus destroying
any auto variables in them), even in the case of
COMING FROM a function into the same function.
auto variables in the function that is come into will
start uninitialised, even if initialisers are given in their
declaration, and it will be a `new' invocation of that function. (It is
quite possible that the uninitialised values in the auto
variables will happen by chance to have the values they had in some
previous invocation of the function, though, because they are likely to
be stored in much the same region of memory; but it is highly unwise to
rely on this.) Note that volatile will not help here.
Observant or source-code-reading readers may note that there is a
mention of an ick_goto in the source code to
C-INTERCAL; this is undocumented and this manual does not
officially claim that such a macro exists (after all, if it did, what
in INTERCAL could it possibly correspond to?), but
if such a macro does exist it obeys the same restrictions as COME
FROM.
FORGET is the worst of all in terms of preserving data on
the stack; it deallocates alloca data and clobbers or
deletes auto variables in all function invocations that
have come into existence since the NEXT that created the
topmost remaining NEXT stack entry was called, or since
the start of the program if the NEXT stack is emptied, and
the current function will continue in a new invocation.
volatile is useless in preventing this, because the
relevant parts of the stack where the data were stored are deleted by
the command (that's what FORGET does, remove stack). If
any of these data are required, they have to be backed up into static
storage (variables declared with static or global
variables), or into heap storage (as in with malloc), or
other types of storage (such as temporary files) which are not on the
stack. (Incidentally, suddenly deleting parts of the stack is excellent
at confusing C debuggers; but even RESUME and COME
FROM tend to be sufficient to confuse such debuggers. More
worrying is probably the fact that the C standard provides a portable
method for deleting the stack like that, and in fact the external calls
runtime library is written in standard freestanding-legal C89 (with the
exception of +printflow debug
output which requires a hosted implementation), meaning that in theory
it would be possible to split it out to create an implementation of a
C-plus-COME-FROM-and-NEXT language, and doing so would not be
particularly difficult.)
Note that INTERCAL variables are not stored on the C stack, nor are any of the metadata surrounding them, and so are not affected unduly by control flow operations.
| INTERCAL-72 | C-INTERCAL | CLC-INTERCAL |
J-INTERCAL
|
|---|---|---|---|
| no | version 0.29+ | no |
no
|
C-INTERCAL supports linking INTERCAL programs with Funge-98 programs (to be precise, only Befunge-98 programs are currently supported). However, it does not ship with a Funge-98 interpreter, and such an interpreter needs to be linked to the resulting program in order to run the Befunge program. Therefore, you need to convert a third-party Funge-98 interpreter to a library usable by C-INTERCAL before you can use this part of the external calls system (see Creating the Funge-98 Library); however, this only has to be done once.
Once the library has been created, you can link an INTERCAL program with a Befunge-98 program by invoking ick like this:
ick -e intercalprogram.i befungeprogram.b98
You can link no more than one Befunge-98 program at once (just like you can link no more than one INTERCAL program at once). Also, the INTERCAL program must come first on the command line.
It is legal to link INTERCAL, C, and Befunge-98 simultaneously; however, the identifiers used in the third-party Funge-98 interpreter have not been mangled to avoid collisions, and therefore problems may be caused if the C program uses the same identifiers as the Funge-98 interpreter.
Before external calls to Funge-98 can be used, the relevant library must be compiled. (After the library has been compiled, then you will need to reinstall C-INTERCAL; however, you will not need to recompile C-INTERCAL.)
At present, only the cfunge Funge-98 interpreter can be converted into a library suitable for use by C-INTERCAL; also, doing this is only supported on POSIX systems (although if someone gets it to work on DOS/Windows, the author of this manual would be interested to hear about it.) Also, a source-code distribution (rather than a binary distribution) is needed. One way to obtain the latest cfunge sources is via the bzr version-control system, using the following command (correct as of the time of writing, but as always, links can become dead):
bzr branch http://rage.kuonet.org/~anmaster/bzr/cfunge
(As a licensing note, note that cfunge is licensed under the GNU General Public licence version 3, whereas C-INTERCAL is licensed under version 2 and all later versions of that licence; although these terms are obviously compatible with each other, you must ensure yourself that your program has appropriate licensing terms to allow a GPLv3 library to be linked to it.)
Once you have downloaded the cfunge sources, you need to compile them into a library suitable for use with C-INTERCAL (note that this is a somewhat different process to compiling them into a standalone Funge-98 interpreter). There is a script provided in the C-INTERCAL distribution to do this, etc/cftoec.sh. It must be run in the etc subdirectory of the C-INTERCAL distribution (i.e. the directory the script itself is in), and must be given the path to the root directory of the cfunge source distribution (that is, the directory that contains the src, lib and tools subdirectories of that distribution) as its only argument. Note that it may give some compiler warnings on compilation; my experience is that warnings about C99 inlining can be safely ignored (they reflect a deficiency in gcc itself that luckily seems to be irrelevant in this case), but other warnings may indicate problems in the exact versions of the sources that you downloaded (and errors definitely indicate such problems).
Once the library has been created, it will appear as the new file lib/libick_ecto_b98.a in the C-INTERCAL distribution (the cfunge distribution will be left unchanged); reinstalling C-INTERCAL will install this file to its proper location. (It is also in a valid location to be able to be run if you aren't installing C-INTERCAL but instead just running it from the distribution's directory.)
This section will not make much sense to a non-Funge programmer; therefore, if you are not used to Funge, you probably want to skip it.
To a Funge program, the external calls interface is accessed via a Funge-98 'fingerprint' defined by the interpreter. The name of the fingerprint is 0x49464649, or as text, ‘IFFI’.
When a program formed by linking INTERCAL and Befunge-98 is run, the first thing that happens is some internal INTERCAL initialisation which is not visible to either program, and then initialisation routines specified in the Befunge-98 program run (if an initialisation routine is also specified in a linked C program using ick_startup, it is unspecified whether the C or Befunge-98 initialisation happens first.) In the Befunge program, the initialisation routine consists of everything that happens until the ‘Y’ command in the ‘IFFI’ fingerprint is run; the author of the Funge-98 must load the ‘IFFI’ fingerprint themselves during this initialisation to access that command. (This is so that the Befunge program ends up complying with the Funge-98 standard; commands not defined in that standard cannot be used until a fingerprint is loaded.) During initialisation, no commands from the ‘IFFI’ fingerprint may be used except ‘Y’ and ‘A’. (If a different command is used, ‘C’, ‘M’, and ‘X’ remove the arguments they would use from the stack (if any) but otherwise do nothing, and the other commands in the ‘IFFI’ fingerprint reflect.)
After the ‘Y’
command is called, the INTERCAL program starts
running; in order for the Befunge program to regain control, it has to
be NEXTed to from the INTERCAL program,
or COME or NEXT FROM the
INTERCAL program, or contain the line label to which
syntax in the INTERCAL program was
CREATEd. (In other words, the normal
INTERCAL ways of transferring information between
parts of a program.) In order to do this, therefore, line labels and
INTERCAL control flow statements must be placed into
the Befunge program.
Code like COME FROM
(100) is a single statement in INTERCAL, but
several statements in Funge-98; therefore, some method of telling the
interpreter where to start executing to look for COME
FROMs, NEXT FROMs, and line labels is needed. The
method used by C-INTERCAL is that of the 'marker'; a
marker is represented by character 0xB7 (a mid-dot in Latin-1) in the
input Funge-98 program, but is transformed to a capital
‘M’ by
ick. (The reason for using a
special character for a marker and transforming it rather than just
using ‘M’ is to
prevent occurences of ‘M’ in comments and string literals, etc.,
having an effect on the control flow of the program.) Whenever a
NEXT or line label is encountered (in the
INTERCAL program, the Funge program or elsewhere),
the Funge program is executed starting from each marker in each
cardinal direction to look for line labels or
COME/NEXT FROMs respectively. Therefore,
COME FROM (100) is written in Funge-98 as
Maa*C (where the M is a marker in the source code), and
likewise the line label (100) would be written as
Maa*L. (This code can be written in any cardinal
direction, that is left to right, top to bottom, right to left, or
bottom to top, but not diagonally or flying.) There are likely to be
unused directions from markers, which will be evaluated too; you can
(and must) close these off by reflecting code execution back into that
marker, another marker, or a non-marker M. Note also that
a marker remains in Funge-space even if the M on the same
square is deleted (the marker itself is not visible to the
g command, though).
Here are the commands in the ‘IFFI’ fingerprint:
A
CREATE syntax in the
INTERCAL program; for details of the format of the
signature, see ick_create. Although
using this command during speculative execution works, doing so is
not recommended; if the target line number for CREATEd
syntax is changed during speculative execution to find the line that
that syntax corresponds to, its effect is delayed until after the
original line is found and execution continues from that point. (Side
effects during speculative execution are never recommended, because
they might or might not be optimised away.)
C
COME FROMs and NEXT FROMs, pops a
line label off the top of the stack and does a COME FROM
that location. During speculative excution to find line labels, pops
the top of the stack and ends that particular speculative execution
as a failure. When not doing speculative execution, pops and discards
the top element of the stack.
D
CREATEd command, and allows access to the arguments that
command has. It pops an integer off the top of the stack, and treats
it as an argument position (0-based, so 0 refers to the first
argument, 1 refers to the second, and so on). Note that providing an
invalid argument number, or running this command when not
implementing a CREATEd command, leads to undefined
behaviour (possibly a reflection, possibly a segfault, possibly
worse).
The command pushes information about the argument chosen onto the stack; the following information is pushed from bottom to top:
.123 would push 123 here, but
.1~.2 would push 0).
CREATEd
instruction was called.
F
FORGETs that many
NEXT stack entries (or all of them if the argument given
is negative).
G
L
COME FROMs and NEXT FROMs, this
command pops and discards the top stack element, then ends that
speculative execution. During speculative execution to find a line
label, this command pops an integer from the top of stack and
succeeds with that integer as the line label (that is, it is possible
to NEXT to an L in the Funge program if a
marker, followed by code to push the correct line number onto the
stack, precedes that L). When not doing speculative
execution, the integer on the top of the stack is used as a line
label (assuming it is in the range 1–65535, otherwise it is
popped and discarded), and a search is made for COME
FROMs and NEXT FROMs aiming for that line label
(including in the INTERCAL program and the Befunge
program itself, as well as programs in any other language which may
be linked in). Note that just as in INTERCAL, it
is possible to NEXT to a line label which has a
COME FROM aiming for it, in which case the COME
FROM will come from that line label as soon as the
NEXT transfers control to it.
M
v
>M5C
^
does exactly the same thing as COME FROM (5), even
when, for instance, it is entered from the left in the Funge
program, rather than gaining control from the line label
(5).)
N
NEXTs to that line label (this may start
speculative execution to look for line labels, but might not if it
isn't needed, for instance if the line label in question is in the
INTERCAL program or in a C program linked to the
Befunge program).
R
NEXT stack, and RESUMEs at
the last item removed. (If the top stack element was zero, negative,
or too large, this will cause a fatal error in the
INTERCAL program.)
S
V
CREATEd argument index and an integer from the
top of stack. (This is undefined behaviour if not in the
implementation of a CREATEd statement, or if the
referenced argument does not exist; as with the D
instruction, 0 refers to the first argument, 1 to the second, and so
on.) If the -a option is not
used, this command does nothing; otherwise, the value of the argument
will be set to the integer. (This involves doing a reverse assignment
if the argument is a non-variable expression, as usual, and causes a
fatal error in the INTERCAL program if the reverse
assignment is impossible or an attempt is made to assign a scalar to
an array.)
X
C, except that it does a NEXT FROM rather
than a COME FROM.
As with external calls to C, terminating any program involved (whether
the INTERCAL program with GIVE UP, the
Befunge program with @ or q, or a C program
with exit()) causes all programs involved to terminate,
and likewise a fatal error will end all programs with an error.
One final point which is probably worth mentioning is that flow control
instructions only record the IP's position and direction, nothing else;
so for instance, if the stack is modified in one part of the code,
those modifications will remain even after a RESUME, for
instance.
| INTERCAL-72 | C-INTERCAL | CLC-INTERCAL |
J-INTERCAL
|
|---|---|---|---|
| no | version 0.29+ | no |
no
|
It is possible to specify other information to the external calls system by using the filename list after all the options are given. To be precise, certain filename patterns are recognised and used to change the options that are used to compile the externally-called files.
The ‘.c99’ extension is treated identically to ‘.c’, except that it causes the file with that extension to be preprocessed as C99 (the more modern version of the C standard, the older C89 is more common), and that all C files involved will be compiled and linked as C99. (This corresponds to -std=c99 in gcc.)
The ‘.a’ extension indicates that an object-code library should be linked in to the final program. This is most commonly used to link in the maths library libm.a and other such system libraries. If the filename is of the form ‘lib*.a’, then the file will be searched for in the standard directories for libraries on your system, and also where the C-INTERCAL libraries are stored (which may be the same place); otherwise, the current directory will be searched. (Specifying libm.a on the command line corresponds to passing -lm to gcc.)
Whatever language your source files are written in, when -e is used (see -e), the compiler will go through much the same steps.
First, the INTERCAL program specified is compiled
into a C program that uses the INTERCAL external
call conventions for its control flow operations. The resulting
‘.c’ file will be
left behind in the same directory (even if -g isn't used); if you look at it, you'll see
the #include <ick_ec.h> line, and the other
hallmarks of an external call program (for instance,
INTERCAL NEXTs will translate into
slightly modified ick_nexts; the modification is simply to
allow the correct line number to be displayed in case of error).
After that, the resulting files are preprocessed twice. First, the C
preprocessor is run on the files; then, a special
C-INTERCAL `preprocessor' is run on the files.
(`Preprocessor' is a bit of a misnomer here, as it's near the end of
the compilation process; `postprocessor' would likely be more accurate,
or maybe `interprocessor'.) Its job is to fix line labels between the
gotos that are used to implement jumping into the middle of a C
function, to assign unique numbers to things that need them, and to
keep track of which functions need to be checked for line labels and
for COME FROMs and NEXT FROMs. The resulting
file will have the extension ‘.cio’; it is almost human-readable,
especially if you run it through a C code indenter, and consists of C
code (or code in whatever language is being linked to the
INTERCAL code, but so far only C is accepted) and
instructions to gcc. The
‘.cio’ file will be
left behind for you to look at, if you like.
Once the ‘.cio’
files have been produced, gcc
is used to compile all the ‘.cio’ files and link them together into an
executable; the executable will have the same name as the
INTERCAL source, minus any extension (and on DJGPP,
assuming that its version of gcc could handle the resulting command line
(not necessarily guaranteed), a ‘.exe’ extension is added), and will consist
of all the C files linked together with the
INTERCAL. Any functions named main in
the C files will be deleted; likewise, if there is a name clash between
any two functions, the one in the file named earlier on the command
line will be used. There is presumably some use for this feature,
although I haven't figured out what it is yet.
Extending this to other compiled languages is mostly a problem of determining how they fit into the INTERCAL control structure, which is not a trivial task, and of figuring out how to link them to C code, which in some cases is trivial (especially if the language is one that gcc can compile!) and in other cases is very difficult. If anyone has any ideas of new languages that could be added to the external calls system, feel free to contact the current C-INTERCAL maintainer with suggestions or patches.
| INTERCAL-72 | C-INTERCAL | CLC-INTERCAL |
J-INTERCAL
|
|---|---|---|---|
| no | version 0.28+ | no |
no
|
The C-INTERCAL distribution comes with libraries that can be used to extend its capabilities; they are implemented using the external call mechanism, and are in effect standard files to include using that mechanism. To use an expansion library, give the -e option to ick (note that this means you cannot use them with the debugger or profiler, nor with multithreaded or backtracking programs), and specify the expansion library's name at the end of the command line (or to be precise, anywhere after the initial INTERCAL file). The libraries themselves are written in C and have a ‘.c’ extension, and are human-readable; C-INTERCAL will look for them in the same places as it looks for the system library (including in the current directory, so you can test your own expansion libraries without having to install them).
Expansion libraries use C identifiers which start with the string ‘ick_my_’ (this is not used by the compiler, and is explicitly not affected by the prohibition on identifiers starting ‘ick_’ when writing an expansion library), and use line labels in the range (1600) to (1699). (Most programs will be avoiding this range anyway, because it's inside the (1000) to (1999) range reserved for the system library, but the system library doesn't use it, in much the same way that the identifiers used are inside the range reserved for the compiler, but the compiler doesn't use them.)
Expansion libraries are available from C-INTERCAL version 0.28; CLC-INTERCAL has a similar concept (that of `preloads'), but implemented a completely different way.
syslibc is an implementation of the base-2 INTERCAL system library in C (see System Library); using it in programs running in other bases is accepted by the compiler, but likely to produce unpredictable results. When using this expansion library, you also need to give the -E option (see -E) so that the main system library is not included, or it will be used in preference to the expansion library. All documented features of the INTERCAL base-2 system library are implemented, but most undocumented features are not, so INTERCAL programs which relied on them (dubious behaviour in any case) will not work with syslibc. The main reason to use this library is to increase the speed of an INTERCAL program; however, note that the speed gains in arithmetic will be accompanied by the performance penalty of using the external calls infrastructure, unless you were already using it.
As an example of using ick_create, a very simple expansion
library is provided to enable a computed NEXT capability, by defining a
new command COMPUNEX. It is used as DO .1
COMPUNEX (allowing any expression in place of the .1), and is
similar to an ordinary NEXT, but has two limitations: it
takes up two NEXT stack entries, and the top one should
not be RESUMEd past or forgotten (thus it isn't a
particularly useful command, except maybe to produce the equivalent of
something like function pointers). By the way, note that
C-INTERCAL avoids computed NEXT mainstream
for much the same way that CLC-INTERCAL avoids
NEXT altogether; it makes things too easy. This example is
provided mostly just to demonstrate the syntax, and the care that needs
to be taken with implementing flow control operators.
‘compunex’ is double-deprecated; an alternative is the following sequence of commands involving computed CREATE:
DO CREATE .1 ABC DO ABC
This sequence emulates all features of NEXT (although it
has different gerunds and is two statements, not one), making it much
more useful for simulating computed NEXT than
COMPUNEX is. (There's no need to avoid forgetting the
return value; although this skips the CREATE cleanup, none
is required because the created statement ABC (any other
statement would do just as well) takes no arguments.)
The C-INTERCAL compiler exists in a world of several other compilers.
The Princeton compiler was the first
INTERCAL compiler available, and compiled
INTERCAL-72. Using convickt (see convickt)
to translate its programs from the original EBCDIC to Latin-1 or
Atari-syntax ASCII is required to run them under the
C-INTERCAL compiler, but apart from that there should be
no problems; everything that that compiler can do can be reproduced by
C-INTERCAL, even including some of its bugs. The only
potential problems may be where constructs were nonportable or dubious
to begin with (such as the IGNORE/RETRIEVE
interaction), or where commands intended to be syntax errors were used
in the program but have a meaning in C-INTERCAL. For extra
portability, it's possible to use the -t compiler option
to ick (see -t) to tell it to interpret the program as
INTERCAL-72, but as C-INTERCAL's dialect of
INTERCAL is basically backward-compatible anyway
this mostly serves to check newer programs for compatibility with older
compilers.
The Atari compiler was another implementation of INTERCAL-72, which was basically identical to the Princeton compiler apart from its use of ASCII and Atari syntax. Everything said under the previous section applies, except that as it uses the same syntax as C-INTERCAL anyway (C-INTERCAL's syntax was based on the Atari compiler's), there is no need to use convickt.
The J-INTERCAL compiler is
an implementation of INTERCAL written in Java that
compiles INTERCAL into Java (and so has a similar
relationship with Java to that of the C-INTERCAL compiler
(which is written in C and compiles into C) with C).
J-INTERCAL has much the same feature set as older versions
of C-INTERCAL, with a few changes (such as the addition of
Esperanto and error messages coming up in different situations).
J-INTERCAL programs should run fine on
C-INTERCAL without trouble (as it is also an Atari syntax
compiler), except in nonportable cases such as
IGNORE/RETRIEVE interaction.
The CLC-INTERCAL compiler is the most modern INTERCAL compiler apart from C-INTERCAL (both compilers are maintained and updated every now and then as of the time of writing, so which is more modern is normally a matter of when you happen to check). Unlike the other three compilers mentioned above, it has a quite significant feature set, including many features not implemented or only partially implemented in C-INTERCAL, and is responsible for the origin of many of the features added in more recent versions of C-INTERCAL. Generally speaking, a CLC-INTERCAL program that uses its advanced features is unlikely to run on C-INTERCAL, or vice versa, whatever you do (apart from completely rewriting the more advanced parts of the program.)
However, there are certain steps that can be taken to transfer less
advanced programs from one compiler to the other. First, translate the
program to Latin-1 Princeton syntax (if translating from
CLC-INTERCAL to C-INTERCAL) or Atari syntax
(if translating from C-INTERCAL to
CLC-INTERCAL), maybe using convickt, if necessary. (Note that here the
program is being translated to the syntax that is not default for the
target compiler.) Then use command-line arguments to switch the
compiler into the correct emulation mode for the other compiler;
C-INTERCAL uses the options -xX, and on CLC-INTERCAL this is
done by selecting the appropriate preloads, or by changing the
program's file extension to ‘.ci’. In each case other options may be
needed to turn on various extensions (maybe -m or -v if translating to C-INTERCAL,
maybe the preload for gerund-based COME FROM if
translating to CLC-INTERCAL), and if translating to
CLC-INTERCAL you need to append the system library to your
program yourself because CLC-INTERCAL doesn't load it
automatically.
In the case of very simple programs, or if you want to spend the effort
in translating compiler-specific code from one compiler to another, you
may be able to work without emulation options. (This is a good target
to aim for, in any case.) In such a case, you would do nothing other
than possibly edit the program to be more portable and a possible
character set and syntax change using convickt. If you need compiler-specific code,
you may be able to detect the compiler in the code itself and adapt
accordingly; making use of the
IGNORE/RETRIEVE interaction is one way to do
this, as it differs between C-INTERCAL,
J-INTERCAL, and CLC-INTERCAL. The other
things to watch out for when doing this are that
CLC-INTERCAL needs an explicit option to enable the use of
NEXT, that CLC-INTERCAL doesn't load the
system library itself (you need to manually append it to the end of the
program) and that you probably shouldn't number a line (666) unless you
know what you're doing, because that line number has a special meaning
in CLC-INTERCAL.
The following table explains the equivalences between the various character sets used for INTERCAL: 7-bit ASCII Atari syntax, 5-bit Baudot Princeton syntax, 8-bit EBCDIC Princeton syntax, and 8-bit Latin-1 Princeton syntax. (The Baudot and EBCDIC are the CLC-INTERCAL versions, which are used by INTERCAL compilers but basically nowhere else.) The characters themselves are not shown in the table below, because they would have to be shown in some syntax, which would be misleading. (Atari syntax is used throughout this manual; you could convert from that, assuming you have an ASCII table handy.) You can also use the convickt command-line tool to translate INTERCAL programs from one format to another (see convickt). Note that Baudot has more than one 'shift state'; the shift state (1, 2, 3, or 4) is written before the hexadecimal code for each character, and * represents a character available in every shift state. To change from one shift state to another, use character 1f to change from shift states 3 or 4 to 1, or from 1 or 2 to 2, and character 1b to change from shift states 1 or 2 to 3, or from 3 or 4 to 4.
| Atari | Baudot | EBCDIC |
Latin-1
|
|---|---|---|---|
| 09 | N/A | 09 |
09
|
| 0a | * 02 | 0a |
0a
|
| 0d | * 08 | 0d |
0d
|
| 20 | * 04 | 40 |
20
|
| 21 | 3 0d | 4f |
21
|
| 22 | 3 11 | 7f |
22
|
| 23 | 4 06 | 7b |
23
|
| 24 | 4 01 | 4a |
a2
|
| 25 | 4 1c | 6c |
25
|
| 26 | 3 1a | 50 |
26
|
| 27 | 3 0b | 7d |
27
|
| 28 | 3 0f | 4d |
28
|
| 29 | 3 12 | 5d |
29
|
| 2a | 4 09 | 5c |
2a
|
| 2b | 4 03 | 4e |
2b
|
| 2c | 3 0c | 6b |
2c
|
| 2d | 3 03 | 60 |
2d
|
| 2e | 3 1c | 4b |
2e
|
| 2f | 3 1d | 61 |
2f
|
| 30 | 3 16 | f0 |
30
|
| 31 | 3 17 | f1 |
31
|
| 32 | 3 13 | f2 |
32
|
| 33 | 3 01 | f3 |
33
|
| 34 | 3 0a | f4 |
34
|
| 35 | 3 10 | f5 |
35
|
| 36 | 3 15 | f6 |
36
|
| 37 | 3 07 | f7 |
37
|
| 38 | 3 06 | f8 |
38
|
| 39 | 3 18 | f9 |
39
|
| 3a | 3 0e | 7a |
3a
|
| 3b | 3 1e | 5e |
3b
|
| 3c | 4 0f | 4c |
3c
|
| 3d | 4 07 | 7e |
3d
|
| 3e | 4 12 | 6e |
3e
|
| 3f | 4 0c | 65 |
a5
|
| 40 | 3 19 | 6f |
3f
|
| 41 | 1 03 | c1 |
41
|
| 42 | 1 19 | c2 |
42
|
| 43 | 1 0e | c3 |
43
|
| 44 | 1 09 | c4 |
44
|
| 45 | 1 01 | c5 |
45
|
| 46 | 1 0d | c6 |
46
|
| 47 | 1 1a | c7 |
47
|
| 48 | 1 14 | c8 |
48
|
| 49 | 1 06 | c9 |
49
|
| 4a | 1 0b | d1 |
4a
|
| 4b | 1 0f | d2 |
4b
|
| 4c | 1 13 | d3 |
4c
|
| 4d | 1 1c | d4 |
4d
|
| 4e | 1 0c | d5 |
4e
|
| 4f | 1 18 | d6 |
4f
|
| 50 | 1 16 | d7 |
50
|
| 51 | 1 17 | d8 |
51
|
| 52 | 1 0a | d9 |
52
|
| 53 | 1 05 | e2 |
53
|
| 54 | 1 10 | e3 |
54
|
| 55 | 1 07 | e4 |
55
|
| 56 | 1 1e | e5 |
56
|
| 57 | 1 12 | e6 |
57
|
| 58 | 1 1d | e7 |
58
|
| 59 | 1 15 | e8 |
59
|
| 5a | 1 11 | e9 |
5a
|
| 5b | 4 10 | 9e |
5b
|
| 5c | 4 05 | N/A |
5c
|
| 5d | 4 13 | 5a |
5d
|
| 5e | 4 0d | 6a |
7c
|
| 5f | 4 15 | 7c |
40
|
| 60 | N/A | N/A |
60
|
| 61 | 2 03 | 81 |
61
|
| 62 | 2 19 | 82 |
62
|
| 63 | 2 0e | 83 |
63
|
| 64 | 2 09 | 84 |
64
|
| 65 | 2 01 | 85 |
65
|
| 66 | 2 0d | 86 |
66
|
| 67 | 2 1a | 87 |
67
|
| 68 | 2 14 | 88 |
68
|
| 69 | 2 06 | 89 |
69
|
| 6a | 2 0b | 91 |
6a
|
| 6b | 2 0f | 92 |
6b
|
| 6c | 2 13 | 93 |
6c
|
| 6d | 2 1c | 94 |
6d
|
| 6e | 2 0c | 95 |
6e
|
| 6f | 2 18 | 96 |
6f
|
| 70 | 2 16 | 97 |
70
|
| 71 | 2 17 | 98 |
71
|
| 72 | 2 0a | 99 |
72
|
| 73 | 2 05 | a2 |
73
|
| 74 | 2 10 | a3 |
74
|
| 75 | 2 07 | a4 |
75
|
| 76 | 2 1e | a5 |
76
|
| 77 | 2 12 | a6 |
77
|
| 78 | 2 1d | a7 |
78
|
| 79 | 2 15 | a8 |
79
|
| 7a | 2 11 | a9 |
7a
|
| 7b | 4 0a | 9c |
7b
|
| 7c | 4 1e | fe |
N/A
|
| 7d | 4 11 | dc |
7d
|
| 7e | 4 0b | a1 |
7e
|
A variety of character sets have historically been used to represent INTERCAL programs. Atari syntax was designed specifically for use with ASCII-7, and all Atari-syntax-based INTERCAL compilers accept that character set as possible input. (C-INTERCAL also accepts Latin-1 and UTF-8.) However, the story is more complicated with Princeton syntax; the original Princeton compiler was designed to work with EBCDIC, but because modern computers are often not designed to work with this character set other character sets are often used to represent it, particularly Latin-1. The CLC-INTERCAL compiler accepts Latin-1, a custom dialect of EBCDIC, Baudot, and a punched-card format as input; C-INTERCAL can cope with Latin-1 Princeton syntax, but for the other character sets, for other compilers, or just for getting something human-readable, it's useful to have a conversion program. convickt is an INTERCAL character set conversion program designed with these needs in mind.
The syntax for using convickt is
convickt inputset outputset [padding]
(that is, the input and output character sets are compulsory, but the parameter specifying what sort of padding to use is optional).
The following values for inputset and outputset are permissible:
? is translated
from Atari to Princeton as a yen sign, and from Princeton to Atari as
a whirlpool (@); this sort of behaviour is often capable
of translating expressions automatically, but will fail when
characters outside ASCII-7 (Atari) or Latin-1 (Princeton) are used,
and will not, for instance, translate a Princeton V,
backspace, - into Atari ?, but instead
leave it untouched. ASCII-7 is a 7-bit character set, so on an 8 bit
computer, there is one bit of padding that needs to be generated;
note, however, that it is usual nowadays to clear the top bit when
transmitting ASCII-7, which the `printable' and `zero' padding styles
will do, but the `random' style may not do.
When using a character set where not all bits in each byte are specified, a third argument can be given to specify what sort of padding to use for the top bits of each character. There are three options for this:
| Option |
Meaning
|
|---|---|
| printable |
Keep the output in the range 32-126 where possible
|
| zero |
Zero the high bits in the output
|
| random |
Pad with random bits (avoiding all-zero bytes)
|
Note that not all conversions are possible. If a character cannot be converted, it will normally be converted to a NUL byte (which is invalid in every character set); note that this will prevent round-tripping, because NUL is interpreted as end-of-input if given in the input. There is one exception; if the character that could not be converted is a tab character, it will be converted to the other character set's representation of a space character, if possible, because the two characters have the same meaning in INTERCAL (the only difference is if the command is a syntax error that's printed as an error message). (The exception exists to make it possible to translate existing INTERCAL source code into Baudot.)
One file in the C-INTERCAL distribution (src/idiotism.oil) is written in Optimizer Idiom Language, a programming language designed especially for expressing optimizer idioms for INTERCAL in an easily editable form (well, at least it's easier than the unmaintainable set of idioms hard-coded in C that were used in previous versions of the INTERCAL compiler).
The structure of an OIL file consists of a sequence of idioms. An optimizer idiom looks for a certain pattern in an expression (which could be an INTERCAL expression, or an expression that has already been partly optimized and therefore contains some non-INTERCAL operators), and replaces it with a replacement that's `simpler' in some sense (in the case of C-INTERCAL, `simpler' is interpreted to mean `compiles into a faster or smaller executable when run through a C compiler'). When an OIL program acts on an input INTERCAL file, it keeps on matching idioms to simplify expressions, until none of the idioms act any more (and if a situation occurs where idioms can keep matching indefinitely, the compiler goes into an infinite loop; so don't allow that to happen); at present, the idioms are tried from left to right, from the leaves of an expression to its root, and from the start of the OIL file to the end; but don't rely on that, because it's subject to change (and gets confusing when you think about what happens when the program actually does a replacement). Anyway, the point is that if an idiom can match an expression, and another idiom doesn't change it first, then the idiom will be matched against that part of the expression eventually, and the program won't end until there are no idioms that match the optimized expression.
At present, the only place that OIL is used in the C-INTERCAL compiler is when the -O option (see -O) is used in base 2. (Syntax is planned to extend OIL to higher bases, and some of this is documented and even implemented, but there's no way to use it.) The idioms are read from the file src/idiotism.oil during the compilation of the C-INTERCAL from sources; you can change the idioms, but you will then have to recompile the distribution (and if you are using the config.sh method, also reinstall, but that will be pretty fast.)
An OIL file is encoded as an ASCII text file using no codepoints outside the range 0-127; using 10 for newline (as on a UNIX or Linux system) is always acceptable, but using 13 then 10 (as is common on Windows or DOS) for newline is acceptable only if your C compiler recognizes that as a newline. I have no idea what happens if you use just 13 on an Apple computer on which that is the common newline convention.
Comments can be given anywhere in
the file by writing lines starting with semicolons (known as hybrids to
INTERCAL programmers). It's also possible to write a
semicolon after part of a line to comment out the rest of the line.
Inside braced C expressions, comments can be given anywhere whitespace
would be allowed by placing them between /* and
*/ (in such cases, the comments will be copied verbatim to
the C temporary files used when building the C-INTERCAL
compiler, where your C compiler will ignore them). Whitespace is
ignored nearly everywhere; the only places it isn't ignored are in the
middle of a decimal constant, inside square brackets, immediately after
one of the characters ‘.:#_}’, and anywhere that C doesn't allow it
in quoted C code. (This means that you can even place it inside
operators like && if you like, as long as they're part of OIL
code and not C code, although doing this is not recommended.) If you
use whitespace in a situation where it isn't ignored, that's almost
certainly an error.
Idioms are grouped into groups of idioms by placing an identifier in square brackets before the group; this follows the rules for C identifiers, except that there's a maximum length of 30 characters. This identifier is the `name' of the group, which has no effect except on optimizer debug output; for that matter, the only effect a group has is that all idioms in the group look the same in optimizer debug output, because they have the same name. It's recommended that idioms only have the same name if they are the same idiom, possibly written in several ways. For example, a shift by 0 has no effect and may as well be removed from the output; the way to express this in OIL is:
[nullshift] (_1 >> #0)->(_1) (_1 << #0)->(_1)
Here, nullshift is the name of the group of idioms, and two idioms are given; one which removes a null rightshift, and one which removes a null leftshift.
As the example above shows, the syntax of an idiom itself is
(pattern)->(replacement)
The parentheses here are actually part of the pattern and/or replacement, and as such sparks (apostrophes) or rabbit-ears (double quotes) can be used instead; they're shown in the syntax because the outer layer of parenthesising is always required. Both the pattern and replacement are OIL expressions, although they both have their own special syntax elements as well.
An OIL expression is built around subexpressions connected by infix binary operators and/or preceded by prefix unary operators, the same way as in C or INTERCAL (although unary operators must be entirely before their argument; the one character later position is not allowed.) As in INTERCAL, there is no operator precedence; expressions must be very fully bracketed to show unambiguously what the precedences must be, and then more so; for instance, bracketing marks must be placed around the argument of a unary operator in most circumstances. Bracketing of expressions can be done with parentheses, sparks (apostrophes) or rabbit-ears (double-quotes).
The following unary and binary operators are allowed in OIL expressions:
$
|
INTERCAL mingle
|
~
|
INTERCAL select
|
&16
|
INTERCAL unary AND (16-bit)
|
V16
|
INTERCAL unary OR (16-bit)
|
?16
|
INTERCAL unary XOR (16-bit)
|
^16
|
INTERCAL unary sharkfin (16-bit)
|
@16
|
INTERCAL unary whirlpool (16-bit)
|
@216..@516
|
INTERCAL unary generalised whirlpool (16-bit)
|
&32
|
INTERCAL unary AND (32-bit)
|
V32
|
INTERCAL unary OR (32-bit)
|
?32
|
INTERCAL unary XOR (32-bit)
|
^32
|
INTERCAL unary sharkfin (32-bit)
|
@32
|
INTERCAL unary whirlpool (32-bit)
|
@232..@532
|
INTERCAL unary generalised whirlpool (32-bit)
|
&
|
C binary bitwise AND
|
|
|
C binary bitwise OR
|
^
|
C binary bitwise XOR
|
+
|
C addition
|
-
|
C subtraction
|
*
|
C multiplication
|
/
|
C integer division
|
%
|
C modulus
|
>
|
C greater than
|
<
|
C less than
|
~
|
C unary bitwise complement
|
!=
|
C not equals operator
|
==
|
C equals operator
|
&&
|
C logical AND
|
||
|
C logical OR
|
>>
|
C bitwise rightshift
|
<<
|
C bitwise leftshift
|
!
|
C unary logical NOT
|
(Note that in some cases two operators are expressed the same way, but that this doesn't matter because one is unary and the other is binary so that there can't be any ambiguity, only confusion. Also note that unlike INTERCAL unary logic operators, OIL unary logic operators must have a bitwidth stated.)
It hasn't yet been explained what operands these operators have to operate on; the syntax for those depends on whether it's a pattern or replacement that the expression is representing.
Patterns are simply OIL expressions; the expressions match either original INTERCAL input or expressions produced by earlier idioms. Each operator must match the same operator in the (possibly partially-optimised) input; the operands themselves are pattern templates specifying what operands in the input they can match.
One special simple form of match is possible:
#NUMBER, where NUMBER is in decimal,
matches a constant with that value. (Unlike in
INTERCAL, this constant is not limited to being a
onespot value; it is, however, limited to being at most twospot, as are
all operands and intermediate values in OIL.)
Otherwise, an operand consists of the following parts, written in order:
_ to specify that any data type can
be matched. In a few cases, you may want to use . or
: to specify that you only want to match a onespot or
twospot value respectively (that is, 16- or 32-bit). You can also use
#; this specifies a value that can be any width, but must
be known to be a constant with a known value at optimize time (either
because it was hardcoded as a constant originally or because a constant
was produced there by the optimizer, for instance via a constant
folding optimization).
{ and
}). This expression is written in C, not
OIL (as are all expressions in braces), and puts an
extra condition on whether the pattern matches. The exact meaning of
this will be explained later.
Note that syntax like #2 is ambiguous given what comes so
far; the first interpretation is the one that is taken in practice, and
if the second interpretation is wanted the operand should be expressed
as #{1}2, using a no-op braced expression to tell them
apart. This particular no-op is recommended because it's detected and
optimized by the OIL compiler.
Braced expressions, which must be written purely in C, add extra conditions; they must return nonzero to allow a possible match or zero to prevent one. They can reference the following variables and functions:
c
cNUMBER
c by
itself refers to the operand to which the braced expression is
attached; if a number is given, it refers to another node (the number
is interpreted as a reference number). The actual value of
c is a 32-bit unsigned integer, each bit of which is
true, or 1, if there is any chance that the corresponding bit of the
operand might be 1, and false, or 0, if it's known for certain that
the corresponding bit of the operand is 0.
For instance:
_{!(c&4294901760LU)}1
The constant given here is FFFF0000 when expressed in hexadecimal;
the point is that the expression matches any operand that is known
to have a value no greater than 65535. Unless the operand is the
argument to a unary AND, this check generally makes more sense than
explicitly specifying . rather than _,
because it will identify both 16- and 32-bit values as long as
they're small enough to fit into a onespot variable. This code
could, for instance, be used to check that an argument to a mingle
must be small enough before optimising it (this is important
because an optimisation shouldn't optimise an error – in this
case, an overflowing mingle – into a non-error).
x
xNUMBER
x is like c, and refers to operands in the
same way, except that it can only refer to an operand marked with
#. It holds the value of that constant (a 32-bit
unsigned integer), which will be known to the optimizer at optimize
time. One common use of this is to detect whether a constant happens
to be a power of 2, although there are many other possibilities that
may be useful.
r
r is the value of the loop counter. (It's almost
certainly a mistake if you have a loop but don't reference the loop
counter at least once, and usually at least twice, within the loop.)
See OIL Loops.
and16
and32
or16
or32
xor16
xor32
iselect
mingle
xselx
xselx(c)
is shorthand for iselect(c,c). When the argument is very
complicated, this can save a lot of space in the original
OIL program.
setbitcount
smudgeright
smudgeleft
smudgeright function
returns its argument but with all the bits less significant than the
most significant bit with value 1 set to 1; likewise,
smudgeleft returns its argument with all the bits more
significant than the least significant bit with value 1 set to 1.
Note that all OIL character is done internally using
unsigned 32-bit numbers, and C expressions you write should do the
same. The practical upshot of this is that you should write
LU after any constant you write in C code; if you don't do
this, you are reasonably likely to get compiler warnings, and the
resulting program may not work reliably, although the
OIL compiler itself will not complain.
Here's a more complicated example of an optimizer operand:
#{!(x&2863311530LU)&&iselect(x,1431655765LU)==
xselx(iselect(x,1431655765LU))}3
It helps to understand this if you know that 2863311530 in hexadecimal is AAAAAAAA and 1431655765 in hexadecimal is 55555555. (It's worth putting a comment with some frequently-used decimal constants in an OIL input file to help explain what these numbers mean and make the code more maintainable.) The operand matches any constant integer which has no bits in common with AAAAAAAA, and for which if any bit in common with 55555555 is set, all less significant bits in common with that number are also set.
Replacements have much the same syntax
as patterns. The expressions are parsed in much the same way; however,
one peculiarity of replacements is that bitwidths must be specified.
INTERCAL has a typecaster that figures out whether
each expression is 16 bits or 32 bits wide, but it runs before the
optimizer, and as the optimizer can produce expressions whose bitwidths
don't obey INTERCAL's rules, this information needs
to be inserted somehow in a replacement. In C-INTERCAL, it
usually doesn't matter what the bitwidth is, and in cases where it
doesn't matter the normal operators ($, ~,
and so on) can be used. (Note that the bit width of the entire
replacement is always set to the same bit width as the bit width of the
expression matched by the pattern; so you don't have to worry about the
effect on unary logical operators that might be operating on the
expression being optimized. This is an exception to the normal bitwidth
rules for a replacement.) In cases where it does matter (due to
C-INTERCAL's lenient interpretation of bitwidth on mingle
inputs, the only place it matters is in the input to
INTERCAL unary logical operators), both the bitwidth
of the operator and the argument on which it operates must be
explicitly given, and given as the same value; to set the bitwidth of
an operator's result, simply write the bitwidth (16 or 32 for onespot
and twospot respectively) immediately after the operator; for instance,
!=32 will generate a not-equals operation with a 32-bit
bitwidth. If an operator's width is set to 16, and during the course of
execution of the optimized program, a value that doesn't fit into 16
bits is encountered, that's undefined behaviour and anything might
happen (most likely, though, the program will just act as though its
width had been set to 32 bits instead); this error condition is not
detected. Also note that operators like &32 already
have a bitwidth specified, so specifying &3232 (or
worse, &3216) is not allowed.
Replacement operands are simpler than pattern operands, because there are only a few forms they can take.
_NUMBER
.NUMBER
:NUMBER
.1 in the pattern
with .1 in the replacement, for instance). You cannot
use #NUMBER here to copy in a constant from
the left-hand side, though, nor #{1}NUMBER,
because the first means something else and the second is undefined
behaviour (that is, no behaviour for the second case has been
specifically implemented in the compiler and therefore its behaviour
is unpredictable and subject to change in future versions); use
_NUMBER to copy over a constant with an
unknown at optimizer compile time (but known at optimize time) value
from the left hand side, as you can do with any other operand being
copied.
#NUMBER
#{EXPRESSION}0
As an example, here's an idiom that moves C bitwise AND operations inside leftshifts. (This is useful because if the optimizer has generated a large sequence of mixed ANDs and bitshifts, moving all the ANDs to one end allows them to be clumped together and optimized down to one AND, whilst the shifts can all be combined into one large shift.)
((_1 << #{1}2) & #{1}3)->((_1 & #{x3>>x2}0) << _2)
When writing idioms, sometimes instead of using very complicated expressions to try to match multiple situations at once it's easier to have a separate idiom for each possible situation; for instance, it's easier to write idioms for right-shift by 1, right-shift by 2, right-shift by 3, etc., rather than a general idiom to rightshift by any amount. When the idioms follow a pattern, as they will do in basically every case of this sort, it's possible to automatically generate them using a loop. For instance, idioms to optimize a one-bit rightshift and a two-bit rightshift are:
(_1~#{xselx(x)<<1==x&&x}2)->((_1&_2)>>#1)
(_1~#{xselx(x)<<2==x&&x}2)->((_1&_2)>>#2)
Adding a loop to automatically generate the idioms, and placing a name for the group of idioms at the start, produces the following code:
[rshift]
<#1-#31
(_1~#{xselx(x)<<r==x&&x}2)->((_1&_2)>>#{r}0)
>
That's 31 different idioms, generated with a loop. As the above example
shows, a loop starts with
<#NUMBER-#NUMBER and
ends with >; a different idiom is generated for each
possible value of the loop counter r in the range given by
the opening line of the loop. Loops must be placed around idioms, but
inside a group of idioms. Note the use of #{r}0 to
generate a constant whose value is equal to the value of the loop
counter.
Here are some tips for the best use of OIL:
MAXTOFREE in oil.y; this isn't a limit on the number of
idioms but on the number of strings that are allocated internally to
process the idioms), and lack of error checking (invalid
OIL may produce errors in the
OIL compiler, or cause the output C code to
contain errors or warnings, or may even appear to work).
To finish off this appendix,
here's an example of the power of OIL; this is the
optimization of an idiom from the INTERCAL-72 system
library, as shown with -H;
this should give a good idea of how OIL programs
work. (All the relevant idioms are in idiotism.oil as of the time of writing.) Note how
the expression is reduced one small step at a time; the smallness of
the steps makes the optimizer more general, because if the original
expression had been slightly different, the optimizer wouldn't have
come to the same result but could have optimized it quite a bit of the
way, up to the point where the optimizations were no longer valid; in
an older version of INTERCAL, this idiom was simply
hardcoded as a special case and so slight variations of it weren't
optimized at all. If you look at the idioms themselves, it'll also be
apparent how c (the record of which bits of an expression
can be 1 and which bits can't be) is important information in being
able to apply an optimization more aggressively.
.3 <- ((((((((.3 $ 0x0) ~ (0x7fff $ 0x1)) $ 0x0) ~ (0x7fff $ 0x1)) $ 0x0) ~ (0x3fff $ 0x3)) $ 0x0) ~ (0xfff $ 0xf)) [minglefold] .3 <- ((((((((.3 $ 0x0) ~ 0x2aaaaaab) $ 0x0) ~ (0x7fff $ 0x1)) $ 0x0) ~ (0x3fff $ 0x3)) $ 0x0) ~ (0xfff $ 0xf)) [lshift16] .3 <- ((((((((((.3 >> 0x0) & 0x7fff) << 0x1) | 0x0) $ 0x0) ~ (0x7fff $ 0x1)) $ 0x0) ~ (0x3fff $ 0x3)) $ 0x0) ~ (0xfff $ 0xf)) [noopor] .3 <- (((((((((.3 >> 0x0) & 0x7fff) << 0x1) $ 0x0) ~ (0x7fff $ 0x1)) $ 0x0) ~ (0x3fff $ 0x3)) $ 0x0) ~ (0xfff $ 0xf)) [minglefold] .3 <- (((((((((.3 >> 0x0) & 0x7fff) << 0x1) $ 0x0) ~ 0x2aaaaaab) $ 0x0) ~ (0x3fff $ 0x3)) $ 0x0) ~ (0xfff $ 0xf)) [lshift16] .3 <- (((((((((((.3 >> 0x0) & 0x7fff) << 0x1) >> 0x0) & 0x7fff) << 0x1) | 0x0) $ 0x0) ~ (0x3fff $ 0x3)) $ 0x0) ~ (0xfff $ 0xf)) [noopor] .3 <- ((((((((((.3 >> 0x0) & 0x7fff) << 0x1) >> 0x0) & 0x7fff) << 0x1) $ 0x0) ~ (0x3fff $ 0x3)) $ 0x0) ~ (0xfff $ 0xf)) [minglefold] .3 <- ((((((((((.3 >> 0x0) & 0x7fff) << 0x1) >> 0x0) & 0x7fff) << 0x1) $ 0x0) ~ 0xaaaaaaf) $ 0x0) ~ (0xfff $ 0xf)) [lshift16] .3 <- ((((((((((((.3 >> 0x0) & 0x7fff) << 0x1) >> 0x0) & 0x7fff) << 0x1) >> 0x1) & 0x1fff) << 0x3) | 0x0) $ 0x0) ~ (0xfff $ 0xf)) [noopor] .3 <- (((((((((((.3 >> 0x0) & 0x7fff) << 0x1) >> 0x0) & 0x7fff) << 0x1) >> 0x1) & 0x1fff) << 0x3) $ 0x0) ~ (0xfff $ 0xf)) [minglefold] .3 <- (((((((((((.3 >> 0x0) & 0x7fff) << 0x1) >> 0x0) & 0x7fff) << 0x1) >> 0x1) & 0x1fff) << 0x3) $ 0x0) ~ 0xaaaaff) [lshift16] .3 <- (((((((((((((.3 >> 0x0) & 0x7fff) << 0x1) >> 0x0) & 0x7fff) << 0x1) >> 0x1) & 0x1fff) << 0x3) >> 0x3) & 0x1ff) << 0x7) | 0x0) [noopor] .3 <- ((((((((((((.3 >> 0x0) & 0x7fff) << 0x1) >> 0x0) & 0x7fff) << 0x1) >> 0x1) & 0x1fff) << 0x3) >> 0x3) & 0x1ff) << 0x7) [nullshift] .3 <- (((((((((((.3 & 0x7fff) << 0x1) >> 0x0) & 0x7fff) << 0x1) >> 0x1) & 0x1fff) << 0x3) >> 0x3) & 0x1ff) << 0x7) [combinelrshift] .3 <- ((((((((((.3 & 0x7fff) << 0x1) & 0x7fff) << 0x1) >> 0x1) & 0x1fff) << 0x3) >> 0x3) & 0x1ff) << 0x7) [andintolshift] .3 <- ((((((((((.3 & 0x7fff) & 0x3fff) << 0x1) << 0x1) >> 0x1) & 0x1fff) << 0x3) >> 0x3) & 0x1ff) << 0x7) [combinellshift] .3 <- (((((((((.3 & 0x7fff) & 0x3fff) << 0x2) >> 0x1) & 0x1fff) << 0x3) >> 0x3) & 0x1ff) << 0x7) [combinelrshift] .3 <- ((((((((.3 & 0x7fff) & 0x3fff) << 0x1) & 0x1fff) << 0x3) >> 0x3) & 0x1ff) << 0x7) [andintolshift] .3 <- ((((((((.3 & 0x7fff) & 0x3fff) & 0xfff) << 0x1) << 0x3) >> 0x3) & 0x1ff) << 0x7) [combinellshift] .3 <- (((((((.3 & 0x7fff) & 0x3fff) & 0xfff) << 0x4) >> 0x3) & 0x1ff) << 0x7) [combinelrshift] .3 <- ((((((.3 & 0x7fff) & 0x3fff) & 0xfff) << 0x1) & 0x1ff) << 0x7) [andintolshift] .3 <- ((((((.3 & 0x7fff) & 0x3fff) & 0xfff) & 0xff) << 0x1) << 0x7) [combinellshift] .3 <- (((((.3 & 0x7fff) & 0x3fff) & 0xfff) & 0xff) << 0x8) [combineand] .3 <- ((((.3 & 0x3fff) & 0xfff) & 0xff) << 0x8) [combineand] .3 <- (((.3 & 0xfff) & 0xff) << 0x8) [combineand] .3 <- ((.3 & 0xff) << 0x8)
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This is the index of everything in this manual. (Note that in some versions of the manual this is called ‘Main Index’ to prevent it transforming into a page called index.html in the HTML version of the manual. The complications that that caused were really odd.)
": Grouping Rules
#: Constants and Variables
$: Mingle
%: Execution Chance
&: Unary Binary Logic
': Grouping Rules
+help: Options to Generated Programs
+instapipe:
Options to Generated
Programs
+mystery:
Options to Generated
Programs
+printflow:
Options to Generated
Programs
+traditional:
Options to Generated
Programs
+wimpmode:
Options to Generated
Programs
,: Constants and Variables
-@: Other Options
-a: Language-affecting Options
-b: Language-affecting Options
-c: Output Options
-C: Language-affecting Options
-d: Debug Options
-E: Language-affecting Options
-e: Language-affecting Options
-F: Optimizer Options
-f: Optimizer Options
-g: Debug Options
-H: Debug Options
-h: Debug Options
-help: Options to Generated Programs
-hH: Debug Options
-instapipe:
Options to Generated
Programs
-l: Debug Options
-m: Language-affecting Options
-mystery:
Options to Generated
Programs
-O: Optimizer Options
-o: Output Options
-p: Debug Options
-P: Language-affecting Options
-printflow:
Options to Generated
Programs
-t: Language-affecting Options
-traditional:
Options to Generated
Programs
-U: Debug Options
-u: Debug Options
-v: Language-affecting Options
-w: Debug Options
-wimpmode:
Options to Generated
Programs
-x: Language-affecting Options
-X: Language-affecting Options
-Y: Debug Options
-y: Debug Options
.: Constants and Variables
/: Operand Overloading
:: Constants and Variables
;: Constants and Variables
?: Unary Binary Logic
@: TriINTERCAL
^: TriINTERCAL
ABSTAIN: ABSTAIN and REINSTATE
ABSTAIN, nonexistent target: Errors
ABSTAINING: ABSTAIN and REINSTATE
AGAIN: ONCE and AGAIN
and16: OIL Patterns
and32: OIL Patterns
c: OIL Patterns
c1--c9: OIL Patterns
CALCULATING:
Calculate
COME FROM: COME FROM and NEXT FROM
COME
FROM, ambiguity: Errors
COME FROM, multithreading: Multithreading using COME FROM
COME
FROM, no target: Errors
COMMENT: Syntax Error
COMMENTING: Syntax Error
COMMENTS: Syntax Error
compunex: Expansion Libraries
config.sh:
Simple Installation
CREATE: CREATE
DO: Statement Identifiers
FORGET: NEXT FORGET and RESUME
FORGETTING: NEXT FORGET and RESUME
GIVE UP: GIVE UP
GO AHEAD: Backtracking
GO AHEAD, no choicepoint: Errors
GO
AHEAD, not enabled: Errors
GO BACK: Backtracking
GO
BACK, no choicepoint: Errors
GO
BACK, not enabled: Errors
ick_comefrom:
ick_comefrom and
ick_nextfrom
ick_comefromif:
ick_comefrom and
ick_nextfrom
ICK_EC_FUNC_END:
External C Call
Infrastructure
ICK_EC_FUNC_START:
External C Call
Infrastructure
ick_forget:
ick_forget
ick_getonespot:
ick_get/setone/twospot
ick_gettwospot:
ick_get/setone/twospot
ick_labeledblock:
ick_labeledblock
ick_linelabel:
ick_linelabel
ick_next: ick_next
ick_nextfrom:
ick_comefrom and
ick_nextfrom
ick_nextfromif:
ick_comefrom and
ick_nextfrom
ick_resume:
ick_resume
ick_return_or_resume:
ick_resume
ick_setonespot:
ick_get/setone/twospot
ick_settwospot:
ick_get/setone/twospot
ick_startup:
ick_startup
IGNORE: IGNORE and REMEMBER
IGNORE/RETRIEVE interaction: STASH and RETRIEVE
IGNORING: IGNORE and REMEMBER
iselect: OIL Patterns
make: Simple Installation
make install:
Simple Installation
MAXTOFREE: OIL Tips
MAYBE: Backtracking
MAYBE,
not enabled: Errors
mingle: OIL Patterns
N'T: Statement Identifiers
NEXT: NEXT FORGET and RESUME
NEXT FROM: COME FROM and NEXT FROM
NEXT FROM, multithreading: Multithreading using COME FROM
NEXT
FROM, no target: Errors
NEXT, nonexistent target: Errors
NEXT,
stack overflow: Errors
NEXTING: NEXT FORGET and RESUME
NOT: Statement Identifiers
ONCE: ONCE and AGAIN
or16: OIL Patterns
or32: OIL Patterns
STASH: Errors
PIN: PIC-INTERCAL
PIN, in a non-PIC program: Errors
PLEASE: Statement Identifiers
PLEASE, proportion required: Errors
r: OIL Patterns
READ OUT: READ OUT and WRITE IN
READING OUT:
READ OUT and WRITE IN
REINSTATE: ABSTAIN and REINSTATE
REINSTATING:
ABSTAIN and REINSTATE
REINTSTATE, nonexistent target: Errors
REMEMBER: IGNORE and REMEMBER
REMEMBERING:
IGNORE and REMEMBER
RESUME: NEXT FORGET and RESUME
RESUME,
by 0: Errors
RESUMING: NEXT FORGET and RESUME
RETRIEVE: STASH and RETRIEVE
RETRIEVE, without stashing: Errors
RETRIEVE/IGNORE interaction: STASH and RETRIEVE
RETRIEVING: STASH and RETRIEVE
SENESTMAX: Errors
setbitcount:
OIL Patterns
smudgeleft: OIL Patterns
smudgeright:
OIL Patterns
STASH: STASH and RETRIEVE
STASHING: STASH and RETRIEVE
SUB: Array Subscript
syslibc: Expansion Libraries
TRY AGAIN: TRY AGAIN
TRY
AGAIN, not last: Errors
V: Unary Binary Logic
WHILE: Multithreading using WHILE
WHILE,
not enabled: Errors
WRITE IN: READ OUT and WRITE IN
WRITING IN: READ OUT and WRITE IN
x: OIL Patterns
x1--x9: OIL Patterns
xor16: OIL Patterns
xor32: OIL Patterns
xselx: OIL Patterns