[Python-Dev] Re: Decimal data type issues

[Jewett, Jim J]

Kevin Jacobs:
> It is well understood that operations on Decimal instances
> must rely on the context.  The idea here is to overflow and 
> round correctly upon instance creation without going through 
> a great deal of additional effort.

Aahz:

> Why do you think this is a "great deal" of effort? 

(1)
If your data comes from an external source, it makes sense to say
"create a decimal from this" instead of "create a string from this,
then a decimal from that, then another decimal from that with the
right rounding."

(2)
If this is done by inheritance, there will quickly be diamond
inheritance.  With a mixin, that is probably OK, but still not
desirable.

(3)
Is there any reason *not* to honor an optional context when
creating a Decimal?  

The machinery is already there when creating one as the result 
of a calculation.  The machinery is even there to change context 
at arbitrary times -- why not allow it on input/output, which is 
when you are most likely to be dealing with an external data source?

-jJ