Path: utzoo!attcan!utgpu!watmath!datanguay
From: datanguay@watmath.waterloo.edu (David Adrien Tanguay)
Newsgroups: comp.lang.c
Subject: New super switch, was Re: The final word on GOTO
Message-ID: <29947@watmath.waterloo.edu>
Date: 7 Oct 89 05:00:33 GMT
References: <6396@ficc.uu.net> <725@thor.wright.EDU> <6430@ficc.uu.net> <4447@buengc.BU.EDU> <867@crdos1.crd.ge.COM> <4462@buengc.BU.EDU> <4467@buengc.BU.EDU>
Reply-To: datanguay@watmath.waterloo.edu (David Adrien Tanguay)
Distribution: na
Organization: U. of Waterloo, Ontario
Lines: 29

In article <4467@buengc.BU.EDU> bph@buengc.bu.edu (Blair P. Houghton) writes:
<Switch provides a method of conditionally splitting the flow-graph,
<but there doesn't exist a dual of it that would describe the joining of
<some subset of the split branches of the flow-graph.
<
<Something like
<
<	switch(fc) {
<		case 'c': stuff under c; break;
<		case 's': stuff under s; break;
<		...
<		case 'u': stuff under u; break;
<
<		cases 'd', 'o', 'x', 'u': stuff for doxu cases; break;
<		cases 'd', 'c', 'u': stuff for dcu cases; break;
<	}

A friend of mine kicked this idea around a few ago when he was
designing a language (Andrew Wright, ForceTwo). You can also have
cases like "anything except 'a', 'b' 'c'", "anything", and "default - i.e.,
anything that isn't explicitly mentioned elsewhere". This kind of flow of
control construct can do some neat things, but it can also lead to
hard to follow code and strange bugs (no "multiple case in switch" errors).
It shouldn't be that hard for the compiler to generate good code for it.
Unfortunately, I don't think it's useful enough to warrant the extra
language complexity. Multiple (sequential) switches would probably mimic
most of the functionality, anyway. Still, it would be fun to play with.

David Tanguay