Re: Division help in python

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Date	Fri, 07 Sep 2012 18:19:17 +0200
From	Jean-Michel Pichavant <jeanmichel@sequans.com>
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To	Ramyasri Dodla <ramyasri20@gmail.com>
Subject	Re: Division help in python
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Ramyasri Dodla wrote:
> Hi All,
>
> I am brand new to python. checking over basic stuff. I came across the 
> problem while doing so. If any body aware of the problem, kindly 
> respond me.
>
> >>> 5/10
> 0
> >>> - 5/10
> -1
>
> The second case also should yield a 'zero' but it is giving a -1
>
Why should it yield 'zero' ?
The definition of the euclidean division : 
(http://en.wikipedia.org/wiki/Euclidean_division)

a = b*q +r with 0≤ r < |b|

With the constraint of r being a positive integer, the couple (q, r) is 
unique:

with a=-5, b=10

-5 = 10*-1 + 5 (q=-1, r=+5)

Note that for the strict Euclidean division, I mean the one allowing r 
to be negative, then

-5 = 10*0 - 5 (q=0, r=-5) is also valid, but I there's still no reason 
to state that it SHOULD be prefered over the other solution.

The uniqueness of the solution for the 1st definition is probably what 
makes python yield -1 instead of 0.

Cheers,

JM

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Re: Division help in python Jean-Michel Pichavant <jeanmichel@sequans.com> - 2012-09-07 18:19 +0200

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