Path: utzoo!attcan!uunet!mailrus!ncar!groucho!steve
From: steve@groucho.ucar.edu (Steve Emmerson)
Newsgroups: comp.lang.c
Subject: Re: IsUnsigned() function?
Message-ID: <8118@ncar.ucar.edu>
Date: 28 Jul 90 23:23:02 GMT
References: <1990Jul27.161339.14712@kfw.COM>
Sender: news@ncar.ucar.edu
Organization: University Corporation for Atmospheric Research (UCAR)
Lines: 12

In <1990Jul27.161339.14712@kfw.COM> will@kfw.COM (Will Crowder) writes:

>What's wrong with:

>#define IsUnsigned(type)	((type)0 - 1 > 0)

Unless I'm mistaken, in ANSI C "(char)0" will, on most machines,
promote to "signed int" due to the value-preserving rule; consequently,
the above expression will always be false on those machines, regardless
of the signedness of "char".

Steve Emmerson        steve@unidata.ucar.edu        ...!ncar!unidata!steve