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+<title>Intercal</title>
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+
+<i>The following article appeared in Computer Shopper (the British magazine
+of that name, not the Ziff-Davis title) around September 1992.</i>
+<hr>
+
+<H1>Intercal -- the Language From Hell</H1>
+
+<I>Where would we be without effective programming languages?</I> <P>
+
+Wait, don't turn the page; that was a rhetorical question. (The
+answer isn't: word-processing on slide rules.) Every once in a while
+it's worth thinking about the matter. Most of us (the lucky ones,
+that is) don't come within spitting distance of programming from one
+day to the next. Those who do, usually don't give any thought to
+them: it's time to write that function so do it, in C or Cobol or
+dBase whatever comes to hand. We don't waste time contemplating the
+deeper significance of the tools we use to do the job. But what would
+we do without well-designed, efficient programming languages? <P>
+
+Go back to slide rules, maybe.<P>
+
+A computer, in a very real sense, is its language. The processor
+speaks in a native tongue, its own machine code: unreadable by humans
+and next to impossible to program in, but nevertheless essential.
+It's the existence of this language which makes the computer such a
+general purpose tool; a hardware platform upon which we layer the
+abstractions, the virtual machines, of our operating systems. Which
+are, when you stop to think about it, simply a set of grammatically
+correct expressions in the computer's internal language. Take the
+humble 386 PC for example. Feed it one set of instructions and it
+pretends to be a cute little Windows machine; feed it another set, and
+something hairy happens -- it turns into a big, bad file server and
+starts demanding passwords and issuing threats. <P>
+
+This flexibility is not an accident. Almost from the start, the
+feature which distinguished computers from their complex calculating
+predecessors was the fact that they were programmable -- indeed,
+universally programmable, capable of tackling any computationally
+tractable problem. Strip away the programmability of the machine and
+you lose the universality. Not to mention the usefulness. <P>
+
+Programming languages, as any fule kno, originated in the
+nineteen-fifties as a partial solution to a major difficulty; machine
+code is difficult to write and maintain and next to impossible to move
+(or port) from one computer to another of a different type.
+Assemblers, which allowed the programmers to write machine code using
+relatively simple mnemonic commands (which were then "assembled" into
+machine code) were an early innovation, but still failed to address
+the portability issue. The solution that finally took off was the
+concept of an abstract "high level" language: and the first to achieve
+widespread use was Fortran. <P>
+
+A high level language is an artificial language with a rigidly
+specified grammar, which can be translated into machine code via a
+program called a "compiler". Statements in the high level language
+may correspond to individual statements, or whole series of
+statements, in the machine language ofthe computer. Indeed, the only
+thing that makes compilation practical is the fact that all computer
+language systems are effectively equivalent; any algorithm which can
+be expressed in one language can be solved in any other, in principle.
+So why are there so many languages? <P>
+
+
+<H2>A load of old cobol'ers</H2>
+
+There are several answers to the question of language proliferation.
+Besides the facetious (some of us don't like Cobol) and the obvious
+(designing languages looks like a Fun Thing to a certain type of
+warped personality), there's the pragmatic reason. Simply put, some
+languages are excellent for expressing certain types of problem, but
+are lousy at dealing with other situations. Take Prolog, for example.
+Prolog is a brilliant language for resolving formal logic propositions
+expressable in the first order predicate calculus, but you'd need your
+head examining if you tried to write an operating system in it. (The
+Japanese MITI tried to do something similar with their Fifth
+Generation Project, and when was the last time you heard of them?
+Right.) Alternatively, take C. C is a wonderful language. It
+combines the flexibility and speed of raw machine code with the
+readability of ... er. Yes, you can re-jig a C compiler to run on
+anything. You can fine-tune it to produce tight, fast machine code
+that will execute on your toaster. Yes, you can write wonderful
+device drivers in it. But, again, you'd need your head examining if
+you set out to write a humongous database application in it. That's
+what Cobol is for; or SQL. So to the point of this article ...
+INTERCAL. <P>
+
+
+<H2>An icky mess</H2>
+
+INTERCAL is a programming language which is to other languages as
+elephants are to deep-sea fishing -- it has nothing whatsoever to do
+with them. Nothing ... except that it's a programming language. And
+it serves as a wonderful example of the fact that, despite their
+theoretical, abstract interchangeability, not all languages are born
+equal. Here's a potted history of the offender: <P>
+
+INTERCAL is short for "Computer Language With No Readily Pronouncable
+Acronym". It was not so much designed as perpetrated at Princeton
+University, on the morning of May 26th, 1972, by Donald R. Woods and
+James M. Lyon. They have been trying to live it down ever since.
+The current implementation, C-INTERCAL, was written by Eric S.
+Raymond (also the author of The New Hacker's Dictionary), and -- god
+help us -- runs on anything that supports C (and the C programming
+tools lex and yacc). <P>
+
+INTERCAL is, in its own terms, elegant, simple and concise. It is
+also flexible and forgiving; if the compiler (called, appropriately
+enough, ick) encounters something it doesn't understand it simply
+ignores it and carries on. In order to insert a comment, just type in
+something that ick thinks is wrong; but be careful not to embed any
+valid INTERCAL code in your comments, or ick will get all excited and
+compile it. There are only two variable types: 16-bit integers, and
+32-bit integers, denoted by .1 (for the 16-bit variable called "1") or
+:1 (for the 32-bit variable named "1"); note that .1 is not equivalent
+to :1 and definitely has nothing to do with 0.1 (unless it happens to
+be storing a value of 0.1). <P>
+
+INTERCAL supports two unique bitwise operators, interleave (or mingle)
+and select, denoted by the "^" and "~" symbols respectively. You
+interleave two variables by alternating the bits in the two operands;
+you select two variables by taking from the first operand whichever
+bits correspond to 1's in the second operand, then pack these bits to
+the right in the result. There are also numerous unary bitwise
+operators, and in order to resolve matters of precedence the pedantic
+may use sparks (') or rabbit-ears (") to group expressions (Don't
+blame me for the silly names: INTERCAL has a character set which is
+best described as creative.) It is not surprising that these operators
+are unique to INTERCAL; the parlous readability of C would not be
+enhanced by the addition of syntax like: <P>
+
+<TT>PLEASE DO IGNORE .1 <- ".1^C'&:51~"#V1^C!12~;&75SUB"V'V.1~</TT>
+<P>
+
+Like any other language, INTERCAL has flow-of-control statements and
+input and output statements. To write something or other into a
+variable, you need the WRITE IN list statement, where list is a string
+of variables and/or array elements. The format of the input data
+should be as numbers, the digits of which are spelt out in english in
+the range ZERO (or OH) to FOUR TWO NINE FOUR NINE SIX SEVEN TWO NINE
+FIVE. To output some information, you need the READ OUT list
+statement, where list again consists of variables. Numbers are
+printed, by default, in the form of "extended" Roman numerals (the
+syntax of which I will draw a merciful veil over), although the
+scholarly may make use of the standard library, which contains
+routines for formatting output in Sanskrit. <P>
+
+Like FORTRAN, INTERCAL uses line numbers which are optional and follow
+in no particular order. Unlike FORTRAN, INTERCAL has no evil,
+unspeakable GOTO command, and not even an IF statement. However, you
+would be wrong to ascribe this to INTERCAL being designed for
+structured programming; it is actually because C-INTERCAL is the only
+known language that implements the legendary COME FROM ... control
+statement (originally described by R. L. Clark in "A Linguistic
+contribution to GOTO-less programming", Comm. ACM 27 (1984), pp.
+349-350). For many years the GOTO statement -- once the primary means
+of controlling the sequence of execution of a program -- has been
+reviled as contributing to unreadable, unpredictable code that is
+virtually impossible to follow because it jumps about the place like a
+kangaroo on amphetamines. The COME FROM statement enables INTERCAL to
+do away with nasty GOTO's, while still preserving for the programmer
+that sense of warm self-esteem and achievement that comes from
+successfully writing a really nasty piece of self-modifying code
+involving computed GOTO's in FORTRAN (Or, for the terminally hip and
+hacker-ish, involving a triple-indirect pointer to a union of UNIX
+kernel data structures in C. Capisce?) Basically, the COME FROM
+statement specifies a line, or lines, which -- when the program
+executes them -- will jump to the COME FROM: effectively the opposite
+of GOTO. <P>
+
+Because INTERCAL contains no equivalent of the NEXT statement for
+controlling whether or not some statement is executed, it provides a
+creative, endearing and unique substitute; abstention. For example, you
+can abstain from executing a given line of code with the ABSTAIN FROM
+(label) form of the command. Alternatively, and more uselessly, you can
+abstain from executing all statements of a specified type; for example, you
+can say <P>
+
+<TT>PLEASE ABSTAIN FROM IGNORING + FORGETTING</TT>
+<P>
+or
+<P>
+
+<TT>DO ABSTAIN FROM ABSTAINING</TT>
+<P>
+
+The abstention command is revoked by the REINSTATE statement. It is a
+Bad Idea to ABSTAIN FROM REINSTATING. It is also worth noting that the
+ABSTAIN syntax is rather confusing; for example, DO ABSTAIN FROM
+GIVING UP is not accepted, although a valid synonym for this is DON'T
+GIVE UP. (GIVE UP is the statement that terminates execution of a
+program. You are encouraged to use this statement at every
+opportunity. It is your only hope of escape.) <P>
+
+The designers of the INTERCAL language believed that source code
+should be easy to understand or, failing that, friendly; in extremis,
+good old-fashioned politeness will do. Consequently, the syntax of
+the language looks a bit odd at first. After the line label (if any)
+there should be a statement identifier; this can be one of DO, PLEASE,
+or PLEASE DO. Programs which are insufficiently polite to the
+compiler may be rejected with the error message PROGRAMMER IS
+INSUFFICIENTLY POLITE; likewise, programs which spend too much time
+grovelling to the compiler will be terminated with extreme
+prejudice. The DO, PLEASE or PLEASE DO is then followed by
+(optionally) one of NOT, N'T, or %n, then a statement: the NOT or
+N'T's meaning should be self-evident, while the %n is merely the
+percentage probability that the following statement will be
+executed. <P>
+
+Of course, with only two binary and three unary operators, it is
+rather difficult for programmers to get to grips with the
+language. Therefore, in a fit of quite uncharacteristic generosity,
+the designers have supplied -- and even partially documented -- a
+library of rather outre subroutines that carry out such esoteric
+operations as addition, subtraction, logical comparison, and
+generation of random numbers. The subroutines will be charmingly
+familiar to those PDP-11 assembly-language hackers among you who are
+also fluent in FORTRAN and SPITBOL. <P>
+
+<H2>Why you should program in Intercal</H2>
+
+INTERCAL, despite being afflicted with these unique features (which,
+arguably, should remain that way) has survived for twenty years and is
+indeed thriving. The relatively recent C-INTERCAL dialect (which
+introduced the COME FROM statement, among other things) has spread it
+far beyond its original domain; the infamy continues, transmitted like
+a malign influence across the Internet. It is a matter of record that
+no computer language has ever succeeded in gaining widespread
+acceptance on the basis of elegance, comprehensibility or
+necessity. Look at FORTRAN, Cobol or C; all of them spread despite the
+fact that better alternatives were available. In fact, there are
+reasons to believe that INTERCAL is the language of the future.<P>
+
+Firstly, INTERCAL creates jobs. Yes, it's true. In general, if a
+particular programming tool is unfriendly, ugly, and absolutely
+essential, the response of management is to throw more programmers at
+it instead of replacing it. INTERCAL is so monumentally difficult to
+use for anything sensible that it is surely destined to be the cause
+of full employment, massive increases in the DP budget of every
+company where it is used, and general prosperity for programmers. <P>
+
+Secondly, once you have learned INTERCAL you will be able to win
+friends and influence people. As the authors point out, if you were to
+state that the simplest way to store a value of 65536 in a 32-bit
+variable is <P>
+
+<TT>DO :1 <- #0$#256</TT>
+<P>
+
+any sensible programmer would say that this was absurd. Since this is
+indeed the simplest way of doing this, they'd be made to look like a
+fool in front of their boss (who, by Murphy's law, would have turned
+up at just that moment). This will have a devastating effect on their
+ego and simultaneously make you look brilliant (until they realise
+that you cribbed this example from the manual, like me. Deep shame.) <P>
+
+Thirdly, INTERCAL helps sell hardware. There's been a lot of fuss
+recently about big corporations inventing gigantic, bloated windowing
+and operating systems that require monstrously powerful computers to
+run on; some cynics suggest that this is because personal computers
+are now so powerful that they can already do anything any reasonable
+individual would want them to, and it's necessary to invent warm furry
+buttons that soak up millions of processor cycles in order to sell new
+equipment. With INTERCAL, you no longer need Windows or OS/2 to slow
+your 486 PC to a crawl! A Sieve of Eratosthenes benchmark (that
+computes all the prime numbers less than 65536), when coded in
+INTERCAL, clocked over seventeen hours on a SPARCStation-1. The same
+program, in C, took less than 0.5 seconds -- thus proving, quite
+clearly, that INTERCAL software is so slow that you absolutely must
+buy a CRAY-3 or equivalent in order to have any hope of getting any
+work out of it. <P>
+
+Consequently, it is quite clear that INTERCAL represents a major
+alternative to conventional programming languages. Anyone who learns
+this language is going to go far -- at least as far as the nearest
+psychiatric institution. Rumour has it that INTERCAL was not entirely
+unrelated to the collapse of the Soviet Union and the success of the
+Apollo missions. It is even reported to improve your sex life and
+restore hair loss! So we warmly advise you to take this utterly
+unbiased report at face value and go forth and get your friendly
+neighbourhood software company to switch to INTERCAL, wherever or
+whatever they may be using right now. You know it makes sense ... <P>
+
+<A HREF="index.html">Return to the INTERCAL Resources Page.</A>
+
+<HR>
+<ADDRESS>Eric S. Raymond <A HREF="mailto:esr@thyrsus.com"><esr@snark.thyrsus.com></A></ADDRESS>
+</BODY>
+</HTML>
+
projects / intercal.git / commitdiff