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From: bright@dataioDataio.UUCP (Walter Bright)
Newsgroups: net.lang.c
Subject: Re:  Two Birds with One Stone
Message-ID: <881@dataioDataio.UUCP>
Date: Thu, 2-Jan-86 13:32:03 EST
Article-I.D.: dataioDa.881
Posted: Thu Jan  2 13:32:03 1986
Date-Received: Fri, 3-Jan-86 08:12:03 EST
References: <874@dataioDataio.UUCP> <864@kuling.UUCP>
Reply-To: bright@dataio.UUCP (Walter Bright
Organization: Data I/O Corp., Redmond WA
Lines: 18

In article <864@kuling.UUCP> thomas@kuling.UUCP (Thomas H{meenaho) writes:
>In article <874@dataioDataio.UUCP> bright@dataio.UUCP (Walter Bright writes:
>>Almost but not quite true. A compiler CANNOT normally replace a divide
>>by a right-shift if it is an integer divide. This is because a right
>>shift of a negative integer is not the same as a divide.
>However most useable processors provide arithmetic shifts which will give
>the right result even if it is a signed divide.

Ok, try this program:

main()
{
	printf("-3/2 = %d\n-3 >> 1 = %d\n",(-3)/2,(-3) >> 1);
}

I think you'll find the results are different, even when the compiler
does an arithmetic right shift! (The difference is the direction in
which rounding occurs.)