Re: Constant divisions, remainders

kelsey@flora.ccs.northeastern.edu writes:
[Right shift isn't the same as division when the dividend is negative.]


torbenm@diku.dk (Torben AEgidius Mogensen) writes:
>This depends on how you define div and mod for negative integers. The most
>usually found "definition" is that div rounds towards 0, and that mod is
>signed. But most mathematicians prefer to make div always round down and
>that mod is nonnegative. ...
>
>I think the round-to-zero rule for div and signed mod are relics from ones
>complement computers, and should be laid to rest.


The problem with this thinking is that you will get inconsistent results
if you divide by a constant power-of-2 versus dividing by a variable with
the same value. And you will get LOTS of bug reports from the compiler
users!


In order to have the round-to-zero rule "laid to rest," first you have to
convince all the hardware designers out there that their DIV instruction
is broken: GOOD LUCK!


                                                                regards,
                                                                joe


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