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From: mcdonald@aries.scs.uiuc.edu (Doug McDonald)
Newsgroups: comp.lang.c
Subject: Re: IsUnsigned() function?
Message-ID: <1990Jul22.154326.19680@ux1.cso.uiuc.edu>
Date: 22 Jul 90 15:43:26 GMT
References: <1990Jul16.214155.5087@Neon.Stanford.EDU> <2936@mtung.ATT.COM>
Sender: usenet@ux1.cso.uiuc.edu (News)
Reply-To: mcdonald@aries.scs.uiuc.edu (Doug McDonald)
Organization: School of Chemical Sciences, Univ. of Illinois at Urbana-Champaign
Lines: 25

In article <2936@mtung.ATT.COM> rdh@mtung.ATT.COM (Ralph Hayon) writes:
>How about this:
>
>	IsUnsigned (a) 

IS what is wanted here a decision as to the **TYPE** of the variable,
signed or unsigned? I assume so. Then I don't see how a function is
possible at all. IT has to have a defined type parameter. Period.

On the other hand a macro should be possible on any given machine.
But can a portable one be written? Portable to any size int (16 bit,
18 bit, 32 bit, 60 bit, 64 bit...), and to ones or twos complement
(sign-magnitude?). This seems like an interesting and useful topic
for comp.lang.c. 

To extend it a bit, how about macros for

is_twos_complement()

is_ones_complement()

word_size(a), which returns the number of bits in a


Doug McDonald