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From: bart@videovax.tv.tek.com (Bart Massey)
Newsgroups: comp.compilers
Subject: Semicolons (Re: Low-Rent Syntax)
Keywords: parse, design
Message-ID: <1990Aug13.214001.16423@esegue.segue.boston.ma.us>
Date: 13 Aug 90 21:40:01 GMT
References: <1990Aug12.205529.11691@esegue.segue.boston.ma.us>
Sender: compilers-sender@esegue.segue.boston.ma.us
Reply-To: Bart Massey <bart@videovax.tv.tek.com>
Organization: Tektronix TV Measurement Systems, Beaverton OR
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Approved: compilers@esegue.segue.boston.ma.us

In article <1990Aug12.205529.11691@esegue.segue.boston.ma.us> Stephen D. Clamage <steve@taumet.com> writes:
> There has been some discussion about *how* to design languages which do
> not need semicolons to separate or end statements.  No one has brought up
> why you would want to.
...
> Finally, beginning programmers are going to make all kinds of errors, for
> all kinds of reasons.  For more-experienced programmers, are semicolon
> errors a real problem -- as big as other kinds of syntax errors?  I'd say
> no.

Well, I'll admit it :-).  I've been programming in C professionally for
about 5 years, and about 1/2 my extra trips into the editor are still to
correct missing semicolons.  I almost never *add* semicolons, though.
This is true of most C programmers I know.  And note that when the added
semicolon does appear, it usually takes the insidious form

	x = 100;
	while( x );/* a nasty case */
	/* 
	 * these comments are intended only to obscure the fact
	 * that the next statement will never be executed...
	 */
		x--;

I claim that a moment's thought tells us why it is that semis are such a big
problem in traditional languages -- we all have been taught a "structured"
style which emphasizes regular use of whitespace, but traditional compiled
languages are completely insensitive to the use of whitespace.

> One example was given of
> 	a = b
> 	    + c
> as being a legal sequence of statements in one language.  Almost certainly
> this was meant to be a single statement.

What made you think this?  The exactly-one-assignment-statement-per-line
convention, a very common idiom across many otherwise widely different
languages (LISP and friends being the most obvious exception I can think of
offhand).  And yet your compiler or interpreter probably wouldn't even
optionally whine about the above, much less refuse to generate code.

If I ever design a C-like language (which is unlikely, since C is
pretty good for this :-), it'll be spec'ed in such a way as to generate
warnings if line breaks appear in funny places, or the indentation
looks wrong.  It's a bit harder to implement, but I'm just plain tired
of debugging code (of my own and others' :-) like

	if( v )
		w;
		if( x )
			y;
	else /*XXX*/;
		z;
					Bart Massey
					..tektronix!videovax.tv.tek.com!bart
					..tektronix!reed.bitnet!bart
[I never found rogue semicolons to be such a problem, but I suspect that
my style uses a lot more braces than yours. -John]
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