[Python-ideas] division oddness

[Chris Rebert]

On Thu, May 6, 2010 at 5:43 PM, Mathias Panzenböck
<grosser.meister.morti at gmx.net> wrote:
> Shouldn't by mathematical definition -x // y be the same as -(x // y)?

Not necessarily, that's only one possible definition; it is the one
that happens to be used in number theory, but it's not the *only*
possible one.
Most programming languages don't choose that definition and instead
choose one of 2 other definitions that use the signs of the operands
to determine what signs a%b and a//b will have (the difference between
the 2 definitions being *which* operand's sign is used).
See http://en.wikipedia.org/wiki/Modulo_operation for a thorough explanation.

> I think this rather odd. Is there any deeper reason to this behaviour? I
> guess changing this will break a lot of code, but why does it behave like
> this?

I would suppose it's what programmers have found more
useful/intuitive. Most programmers aren't number theorists.

Cheers,
Chris
--
http://blog.rebertia.com