Re: Q: division vs multiplication

gsc@magna.com.au writes:
> The problem here is that -1 divided by 2 should give -1, with a remainder
> of +1. Unfortunately, it's hard to find hardware that does this right.
> Most HLLs (even C!) leave division of negative integers to the conscience
> of the implementor, though. The obvious solution is to implement division
> to round towards -infinity _in all cases_, and you can then use shifts
> with a clear conscience.




Surely the correct approach is for the language definition to state
explicitly what the rules are for truncation, rounding, etc. - then
the programmer knows what to expect in any given situation.


In the extracted text above, if


            -1 :/ 2 = -1, { where :/ is integer division )


  then


            - (-1 :/ 2) = 1 <> 1 :/ 2


  which seems counter-intuitive to me.


--
Roger Barnett
Natron Software Maintenance Ltd, York, England
--

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