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From: ka@hropus.UUCP (Kenneth Almquist)
Newsgroups: net.lang.c
Subject: Re: Integer division
Message-ID: <261@hropus.UUCP>
Date: Tue, 11-Feb-86 02:46:56 EST
Article-I.D.: hropus.261
Posted: Tue Feb 11 02:46:56 1986
Date-Received: Wed, 12-Feb-86 08:09:11 EST
References: <11603@ucbvax.BERKELEY.EDU> <4917@alice.UUCP> <11671@ucbvax.BERKELEY.EDU> <731@abic.UUCP>
Organization: Bell Labs, Holmdel, NJ
Lines: 17

> Perhaps K&R thought that the performance penalty of implementing a
> consistent modulus (or divide) was not justified, since negative
> integers are rarely encountered in "C" [this comment cannot be traced
> to K&R.]  However, this performance penalty can be avoided simply by
> declaring unsigned integers as "unsigned int".

On the VAX, the unsigned remainder function is implemented as a
subroutine call.  The standard divide instruction cannot be used
because the divide instruction does not work on unsigned integers.

In Ada, division truncates towards zero, and there are separate
remainder and modulo operators.  The % operator in C is a remainder
operator; we could have a new operator %% for modulo.  (On the other
hand, maybe not.  We don't want C to get as large as Ada!)
				Kenneth Almquist
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