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From: karl@haddock.ISC.COM (Karl Heuer)
Newsgroups: comp.lang.c
Subject: Re: gotos and switch statements -- mild proposal
Message-ID: <1022@haddock.ISC.COM>
Date: Mon, 31-Aug-87 11:44:47 EDT
Article-I.D.: haddock.1022
Posted: Mon Aug 31 11:44:47 1987
Date-Received: Fri, 4-Sep-87 05:24:20 EDT
References: <855@tjalk.cs.vu.nl> <2683@hoptoad.uucp> <916@haddock.ISC.COM> <929@haddock.ISC.COM> <867@mcgill-vision.UUCP>
Reply-To: karl@haddock.ima.isc.com (Karl Heuer)
Organization: Interactive Systems, Boston
Lines: 25

In article <867@mcgill-vision.UUCP> mouse@mcgill-vision.UUCP (der Mouse) writes:
>In article <929@haddock.ISC.COM>, karl@haddock.ISC.COM (Karl Heuer) writes:
>> In article <2182@zeus.TEK.COM> dant@tekla.UUCP (Dan Tilque) writes:
>>> [switch statements with auto-break breaks "case foo: case bar: ...;"]
>>> One possibility is separating them with commas: "case CR, LF:" which
>>> changes the meaning of the comma operator.
>
>> The comma operator is neither necessary nor useful in a constant
>> expression, and is explicitly disallowed by ANSI.
>
>[Not necessary, but possibly useful in that it might be constructed by a
>general-purpose macro]

Good point (even though I also fail to have an example at hand).  However, the
fact that it *is* currently forbidden means that the proposed syntax would be
fully compatible.  If ANSI later decides to legalize the comma operator in a
constant expression, they could still do so.  This would not conflict with the
proposal -- it would simply create another reason for the macro body to be
enclosed in parens.

In other words, "case CR, LF:" would have the new semantics, whereas
"case (CR, LF):" would be equivalent to "case LF:".  This is no more
problematic than the current overloading of comma for function calls.

Karl W. Z. Heuer (ima!haddock!karl or karl@haddock.isc.com), The Walking Lint