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Path: utzoo!attcan!uunet!ogicse!mintaka!mit-eddie!mit-amt!mob
From: mob@mit-amt.MEDIA.MIT.EDU (Mario O. Bourgoin)
Newsgroups: comp.software-eng,comp.lang.ada,comp.lang.c,comp.lang.fortran,comp.lang.lisp,comp.lang.misc,comp.lang.modula2,comp.lang.pascal,comp.lang.scheme
Subject: Re: Case statements in sane languages
Message-ID: <1925@mit-amt.MEDIA.MIT.EDU>
Date: 19 Mar 90 19:38:50 GMT
References: <9003191549.AA01608@sn1987a.compass.com>
Reply-To: mob@media-lab.media.mit.edu (Mario O. Bourgoin)
Organization: MIT Media Lab, Cambridge MA
List-Id: <comp.lang.ada>

I feel I must interject a some Scheme code in this otherwise C-based
discussion cross-posted to comp.lang.scheme.  In Scheme, there's a
control construct called CASE which is much like C's SWITCH except
that doesn't allow the clauses to be cascaded but it does allow
multiple constants per clause.  It's easy to imagine a CASE-EVERY (in
the spirit of ZETALISP's COND-EVERY) very similar to CASE but that
evaluates every clause whose constant part includes the key.  The
resulting structure passes control more explicitly than its C
equivalent, and yet remains simple enough to encourage programmers to
use it.  For example:

	(case-every (0
		     (1+ count))
		    ((0 1)
		     (1+ ocount))
		    ((0 1 2)
		     (writeln count ocount))
		    (else
		     (writeln "unknown n")))

--Mario