Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Posting-Version: version B 2.10.1 6/24/83 (MC840302); site mcvax.UUCP
Path: utzoo!watmath!clyde!burl!ulysses!mhuxl!houxm!vax135!cornell!uw-beaver!tektronix!hplabs!hao!seismo!mcvax!guido
From: guido@mcvax.UUCP (Guido van Rossum)
Newsgroups: net.lang.c
Subject: Re:  modulus fn with negatives
Message-ID: <5972@mcvax.UUCP>
Date: Mon, 10-Sep-84 17:25:56 EDT
Article-I.D.: mcvax.5972
Posted: Mon Sep 10 17:25:56 1984
Date-Received: Fri, 14-Sep-84 07:27:55 EDT
References: <13079@sri-arpa.UUCP> <8213@umcp-cs.UUCP>
Reply-To: guido@mcvax.UUCP (Guido van Rossum)
Organization: "Stamp Out BASIC" Committee, CWI, Amsterdam
Lines: 22

How about this modulus function:

	mod(a, b) {
		int m = a % b;
		if ((m < 0) != (b < 0)) m += b;
		return m;
	}

This one even works for negative b.
You can also do the following:

	#define mod(a, b) (a%b + b) % b

which should, of course, be written as

	#define mod(a, b) (((a)%(b) + (b)) % (b))

and this also works for negative b (but watch side effects!).

--
	Guido van Rossum, "Stamp Out BASIC" Committee, CWI, Amsterdam
	guido @ mcvax