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From: gary@bocklin.UUCP
Newsgroups: net.lang.mod2
Subject: Re: Aren't people fed up with semicolons yet?
Message-ID: <125@bocklin.UUCP>
Date: Fri, 12-Apr-85 13:39:05 EST
Article-I.D.: bocklin.125
Posted: Fri Apr 12 13:39:05 1985
Date-Received: Sun, 14-Apr-85 06:49:07 EST
References: <4003@mit-eddie.UUCP>
Organization: Dept of CS, U of Arizona, Tucson
Lines: 41

> Has anyone though of trying to see what would happen to Modula-2 syntax if
> semicolons were optional, as in CLU? 
>  ...
> It just seems strange that one language (CLU) would not require explicit
> terminators but another (Modula-2) would.  After all, compilers can be
> made smart enough to allow humans to type fewer superfluous symbols.
> 					- Ralph

Beware the ``superfluous'' claim.  It has gotten us such wonders as
the ``='' vs ``=='' problems in C.  Certainly it is possible to make
semicolons optional, but it has had strange side-effects, in the past.
In an early version of Icon (I have not checked the problem recently),
the code segment

	a:= ( ... very long expression  ... )
	    + (another long expression) ;

was treated as *two* statements. (Expressions really.  Icon, like C,
is an expression language.)  ``a'' was assigned the value of the first
expression and the second value was thrown away.  After tearing hair,
I finally figured out the problem and tried

	a:= (  ( ... very long expression  ... )
	       + (another long expression)   );

expecting the extra parentheses to make the expression one.  Instead I
got a syntax error complaining about the missing right parenthesis
before the ``optional'' semicolon at the end of the first line, and a
second error about the extra right parenthesis on the second line.
The correct ``fix'' was to write

	a:= ( ... very long expression  ... ) +
	    (another long expression) ;

The compiler was smart enough to know that ``optional'' semicolons
don't follow operators.  The real problem was that I couldn't get a
good explanation of when ``optional'' semicolons would be inserted.
It certainly didn't save me any work that day.  Notice that I wasn't
even making use of the feature.
-- 
Gary Levin / Dept of CS / U of AZ / Tucson, AZ 85721 / (602) 621-4231