Newsgroups: comp.lang.misc
Path: utzoo!utgpu!tmsoft!mason
From: mason@tmsoft.uucp (Dave Mason)
Subject: Re: colon-equal vs equal
Message-ID: <1988Dec30.025022.2883@tmsoft.uucp>
Followup-To: comp.lang.misc
Summary: PL/I is worse yet.  + some actual content relevant to the subject line
Reply-To: mason@tmsoft.UUCP (Dave Mason)
Organization: TM Software Associates, Toronto
References: <3300001@uxg.cso.uiuc.edu> <3290002@hpctdls.HP.COM> <2567@ficc.uu.net>
Date: Fri, 30 Dec 88 02:50:22 GMT

In article <2567@ficc.uu.net> peter@ficc.uu.net (Peter da Silva) writes:
>This has nothing to do with :=/= versus =/==. This has to do with C being an
>expression-based language and Pascal being a statement-based language. There
>are expression-based languages which use := and allow you to say things like
>"if flag := f1 and f2 then...".
What it really has to do with is that something that your fingers learn to do:
	if abc = def then ghi :=jkl;
in Pascal becomes:
	if (abc = def) ghi := jkl;
occasionally when you are writing in C (for the first 2-3 years after
switching (may your Deity help you if you don't in fact switch, but alternate
back and forth :-)).  The compiler nicely points out the :=, but leaves you
with the nasty bug:
	if (abc = def) ghi = jkl;
which is your finger's mistake, not even your brain....can be a very hard
bug to find.
>
>Just so long as you have two tokens. If you want to flame a language, try
>BASIC ("if a = b then a = c"... the first is a comparison, the second an
>assignment).
If you want to flame a language, try PL/I:
	if if = then then then = else else else = if;
(there may be some ';' missing, but this is an otherwise legal statement!)
The problem is that there aren't any REAL keywords.  The parser must be a zoo!

(...and while we're PL/I bashing, how about:
	i = 25/3;
which assigns some WEIRD value like 5 to i because of weird default typing &
coercion rules!)

But there are some 'features' :-) in the language: e.g. substr is a function
that takes part of a string, and bit is a function that converts an integer
into a string of bits:
	substr(bit(i),6,17) = substr(bit(j),3,17))
transfers a 17 bit field between part of two integers.  Details may be off,
as it's been about 5 years since I wrote my one (1) PL/I program (2000 lines!),
but the principle's right.  I think the committee that designed the language
was on acid most of the time.

	../Dave