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From: asw@rlvd.UUCP (Antony Williams)
Newsgroups: net.arch
Subject: Re: Right shift vs. divide (change divide!)
Message-ID: <1027@rlvd.UUCP>
Date: Tue, 21-Jan-86 13:59:37 EST
Article-I.D.: rlvd.1027
Posted: Tue Jan 21 13:59:37 1986
Date-Received: Sun, 26-Jan-86 05:15:20 EST
References: <124000005@ima.UUCP> <4772@alice.UUCP> <1016@turtlevax.UUCP> <32@calgary.UUCP>
Reply-To: asw@rlvd.UUCP (Antony Williams)
Organization: Rutherford Appleton Laboratory, Atlas Buildings, U.K.
Lines: 31

In article <32@calgary.UUCP> radford@calgary.UUCP (Radford Neal) writes:
>Rather than get rid of the arithmetic right shift, one could instead
>change the divide instruction so it does what mathematicians have
>always thought division meant.
	this looks like opinion to me.
>
>Specifically:
>
>      Quotient of -3 divided by 2 should be -2.
>      Remainder of -3 divided by 2 should be 1.
>
>With this definition, a right shift divides by two and masking off
>the lower bit gives you the remainder.
>
>Does anyone know any reason, other than inertia, why divides shouldn't
>be changed to work this way.
  Unfortunately, this breaks one of the equivalences that programmers
tend to expect on intuitive grounds, namely:

    - ( a div b ) == ( -a div b ) == a div (-b)

by analogy with real arithmetic.



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