Re: [Pyobjc-dev] NSDecimalNumber to the next level

[Pierce T.W. I. <pi...@tw...>]

>
> I completely forgot to mention that the usual numeric operators do  
> work correctly, as long as you manually convert floats to NSDecimal,  
> e.g. ``NSDecimalNumber.zero() + 4`` is valid code and will do what you  
> want.

Hmmm.... That must have changed, because I submitted a change which you  
accepted awhile back to not implicitly convert. Checking...

 >>> print type(Foundation.NSDecimalNumber.zero())
<type 'float'>

Arrgh, its converting again. That works because Python converted it  
implicitly to a float. (Which is actually kind of surprising, since I  
thought it had stopped doing that. See comment for (Bug #831774) in  
objc/objc_support.m)

This code doesn't work now though:

 >>> print  
Foundation.NSDecimalNumber.numberWithDouble_(3.3).decimalNumberByAdding_ 
(Foundation.NSDecimalNumber.numberWithDouble_(4.4))Traceback (most  
recent call last):
   File "<stdin>", line 1, in ?
AttributeError: 'float' object has no attribute 'decimalNumberByAdding_'

Again, because of the implicit float conversion, which then can't  
convert back.


> Automaticly converting floats to NSDecimal is easy enough, it is a  
> couple of extra lines in Modules/Foundation/decimal.m (I'm not 100%  
> sure about the filename, but it should be close).

   Ok, I'll poke around and see what I can figure out then. I'll have to  
think about all the use cases anyways, since what I really want is:

case 1:   do math in python with NSDN without having to call  
doubleValue()
      print Foundation.NSDecimalNumber.zero()+4

case 2:   yet be able to call NSDN methods?
print  
Foundation.NSDecimalNumber.numberWithDouble_(3.3).decimalNumberByAdding_ 
(Foundation.NSDecimalNumber.numberWithDouble_(4.4))

case 3:   and pass NSDN back to objc
    object.setDecimalNumberValue_(4.4)   (call objc method that takes an  
NSDN)

    To all work.

    Hmm... You know, really, since NSDN is a superset of NSNumber, if  
PyObjC always passed NSDecimalNumbers back to objc instead of  
NSNumbers, things would mostly work. I couldn't do case 2, but I'm not  
sure I'd care then. Though being able to do:

Foundation.NSDecimalNumber.numberWithDouble(3.3).decimalNumberByMultiply 
ingBy_withBehavior_(3.4, pennyRounding)

Is useful. Hmmm.. Adding all the NSDecimalNumber methods to the Python  
float type would work then.

  Arrgh. Brain hurts now. Need more coffee.

  Pierce