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From: djones@megatest.UUCP (Dave Jones)
Newsgroups: comp.theory,comp.misc,comp.lang.misc
Subject: Re: Modulus (Re: hashing function for strings)
Message-ID: <12077@goofy.megatest.UUCP>
Date: 21 Feb 90 01:45:10 GMT
References: <2367@castle.ed.ac.uk>
Organization: Megatest Corporation, San Jose, Ca
Lines: 16

In article <E1wt*4@cs.psu.edu> flee@shire.cs.psu.edu (Felix Lee) writes:
> There are three things that most people would like:
>	quotient = -5 div 3 = -(5 div 3) = -1
>	remainder = -5 mod 3 = (-5 + 6) mod 3 = 1
>	3*quotient + remainder = -5
>
>Unfortunately, they're mutually contradictory.  You must choose one of
>them to violate.  Someone will be unhappy with your decision.
> 

I differ. The first of these, -5 div 3 == -1 is wrong.
-5 div 3 is -2. Fix that, and everything is cool. Draw both versions
of the 'div-3' graph, and you'll see why this makes sense.

The -5 div 3 == -1 graph has an ughliness in it around zero that translates
into an extra test in algorithms.