Path: utzoo!utgpu!jarvis.csri.toronto.edu!torsqnt!tmsoft!masnet!canremote!mark.levy
From: mark.levy@canremote.uucp (MARK LEVY)
Newsgroups: comp.lang.c
Subject: Re: is this broken or what?
Message-ID: <90020407120313@masnet.uucp>
Date: 4 Feb 90 10:23:00 GMT
Organization: Canada Remote Systems Limited, Mississauga, ON, Canada
Lines: 35

dP>Are we to infer from this discussion that the ANSI standard requires
dP>comparisons like the one we are talking about to work properly?  That
dP>is, what is the prescribed behavior of

dP>        int i=MAXINT, j=(-MAXINT);
dP>        if (i > j) printf ("foo");

dP>Since i-j is negative, not positive, I would expect most compilers
dP>*not* to print "foo".
   
   I am not up on the ANSI standards that have been proposed, but as
I recall, the K&R standard was 0 == FALSE and anything else == TRUE.

dP>I don't even know what happens when you compare an unsigned value to a
dP>signed value.  That is, in the test

dP>        unsigned int i;
dP>        if (i >= 0) ...

   The use of 2's complement will avoid any kind of problem of 
positive or negative zero.  A compiler might flag an incompatible
data type comparison here.  My guess is that if the high order bit
in i is set, the expression will evaluate false, provided that it
compiled.

dP>is i converted to a signed type before the comparison is performed?
dP>This could certainly make a mess if i is all ones.

   Don't ever assume anything about type conversions.  If you're not
sure, use pleanty of casts and parens.

Mark
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