Path: utzoo!attcan!utgpu!watmath!iuvax!uxc.cso.uiuc.edu!dino!atanasoff!hascall
From: hascall@atanasoff.cs.iastate.edu (John Hascall)
Newsgroups: comp.lang.c
Subject: Re: "arithmetic if":: Re: Feature for the next C version
Message-ID: <1287@atanasoff.cs.iastate.edu>
Date: 2 Aug 89 14:37:36 GMT
References: <55480@tut.cis.ohio-state.edu> <1989Jul20.152935.14872@utzoo.uucp> <67@motto.UUCP> <18764@mimsy.UUCP> <1389@crdgw1.crd.ge.com> <8515@batcomputer.tn.cornell.edu> <1429@crdgw1.crd.ge.com>
Reply-To: hascall@atanasoff.cs.iastate.edu.UUCP (John Hascall)
Organization: Iowa State Univ. Computation Center
Lines: 42

In article <1429@crdgw1.crd.ge.com> davidsen@crdos1.UUCP (bill davidsen) writes:
 
>someone pointed out, I'm not looking for arithmetic IF, but a way to do
>three separate things based on a value, usually the compare of two
>values in a sort or tree search.
 
>  Some interesting ideas:
>	ifcase
>	  (a < b) code; code;
>	  (a == b) more(code);
>	  (a > b) still(more);
>	endcase;
 
    This reminds my of an exec language I somtimes program in (no, you
    haven't heard of it), where you use:

    cases begin
	case (expression1) statement1
	case (expression2) statement2
	    :
	    :
    end

    And it evaluates each expression in order and executes the (possibly
    compound) statement of the first one (if any) which is true.
    [and you just use "case (true)" at the end for "default:"].

    Of course, neither of these solve the original problem of how to
    execute a 3-way branch with a single expression evaluation.

    Imagine extending the concept:

       if (expr) s1; [else s2;]

    to:

       negative (expr) s1; [zero s2;] [positive s3;]

 
    I can hear the C-purists screaming in agony :-)

John Hascall