[Python-Dev] Floor division

[Anders J. Munch]

Tim Peters wrote:
> Please read the whole thread.  Maybe you did, but you said nothing
> here that indicated you had.  The issues aren't about tiny integers
> that happen to be in float format, where the result is exactly
> representable as a float too.  Those don't create problems for any
> definition of mod.  But even non-tiny exact integers can.

I did read the whole thread, and I saw your -1%1e100 example.  Mixing
floating-point numbers of very different magnitude can get you in
trouble - e.g. -1+1e100==1e100.  I don't think -1%1e100 is all that
worse.

> > It's only Decimal.__mod__ that's inconsistent.  float.__mod__ has the
> > usual floating-point inaccuracies, but then with float that goes with
> > the territory.
> 
> No.  Decimal.__mod_  always returns the mathematically exact result.

I meant inconsistent with integers.  People are familiar with the
semantics of % on integers, because they use it all the time.  % on
float is a natural extension of that and hence unsurprising.  % on
Decimal is exact and correct, but surprising all the same.

regards, Anders