...
[Facundo]
>> We'll have to deprecate that functionality, with proper warnings (take
>> not I'm not following the thread that discuss the migration path to 3k).
>>
>> And we'll have to add the method "remainder" to decimal objects (right
>> now we have only "remainder_near" in decimal objects, and both
>> "remainder" and "remainder_near" in context).
[Raymond]
> Whoa. This needs more discussion with respect to the decimal module. I'm
> not ready to throw-out operator access to the methods provided by the spec.
decimal's __floordiv__ and __divmod__ have nothing to do with the
spec. They were Python-specific extensions apparently added to try to
fit in better with Python's entirely different (than either of
decimal's) definition of modular reduction. In that respect they
succeeded by being jarringly perverse: decimal's __floordiv__(a, b)
does not return the floor of a/b, it returns a/b truncated toward 0:
>>> -1 // 10
-1
>>> Decimal(-1) // Decimal(10)
Decimal("-0")
Even you might agree that's an odd thing for a function named "floor
div" to do ;-)
I say that's not useful. The only method here that does have
something to do with the spec is decimal's __mod__, an implementation
of the spec's "remainder" operation. Guido agreed last May to take
away the "%" infix spelling of mod for binary floats, and I can't
think of a reason for why decimal floats should be immune.
> Also, I do not want the Py2.x decimal module releases to be complexified
> and slowed-down by Py3.0 deprecation warnings. The module is already slow
> and has ease-of-use issues.
We're not talking about the usual arithmetic operations here, just
"%". The functionality wouldn't go away, just the infix 1-character
spelling. Note that the implementation of "remainder" is
extraordinarily expensive, just as the implementation of fmod for
binary floats is extraordinarily expensive: it's not just the
precision at work, but also the difference in exponents.
+ - * / don't have the latter factor to contend with (hence
"extraordinarily"). Couple this with that floating mod of any kind is
almost surely rarely used, and worry about the overhead of a method or
function spelling seems a waste of tears.
Irony: I've used decimal's remainder_near in real life, which has no
operator spelling. I haven't used decimal's `remainder` except to
give examples in this thread :-)
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