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From: jimc@ucla-cs.UUCP
Newsgroups: net.lang.c,net.arch
Subject: Re: Integer division
Message-ID: <8966@ucla-cs.ARPA>
Date: Thu, 13-Feb-86 19:55:59 EST
Article-I.D.: ucla-cs.8966
Posted: Thu Feb 13 19:55:59 1986
Date-Received: Sun, 16-Feb-86 04:22:50 EST
References: <332@ism780c.UUCP> <11603@ucbvax.BERKELEY.EDU> <11610@ucbvax.BERKELEY.EDU> <561@jplgodo.UUCP>
Reply-To: jimc@ucla-cs.UUCP (Jim Carter)
Distribution: net
Organization: UCLA Computer Science Department
Lines: 27
Xref: watmath net.lang.c:7862 net.arch:2523

In article <561@jplgodo.UUCP> steve@jplgodo.UUCP (Steve Schlaifer x3171 156/224) writes:
>If you think of % as returning the *mathematical* remainder of a/b then
>it should return a value >=0.  On the other hand, to be consistent with this
>view, the quotient operator (/) will also have to be modified to preserve
>the formulae
>
>       b=qa+r (0<=r<a)
>       q=b/a
>
>i.e. (-3)/2 must be -2 if (-3)%2 is 1. But this then means that (|a|)/b is not
>the same as |a/b| for a<0. Maybe *An Angry Number Theorist* wants this, but...
>
Right on!  Invariably when I integer-divide negative numbers I have to do
fancy coding to cause (-3)/2 to come out -2 rather than -1.  I would very
much like to see the quotient of *signed* integers come out this way auto-
matically.  However, most hardware doesn't cooperate, necessitating extra
compiled code.  I hope the compiler would have a separate, more efficient
code macro for the unsigned case, so that users concerned with efficiency
and knowing about their hardware could avoid useless overhead by declaring
unsigned ints.
   This kind of efficient compilation would be helped if all int constants
were automatically unsigned.  In other words, the compiler would interpret
-5 as (unary negate operator)(cast to signed)(unsigned int ={5}).

James F. Carter            (213) 206-1306
UCLA-SEASnet; 2567 Boelter Hall; 405 Hilgard Ave.; Los Angeles, CA 90024
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