[Python-Dev] Re: Decimal data type issues (original) (raw)

Jewett, Jim J jim.jewett at eds.com
Tue Apr 20 13:04:44 EDT 2004

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

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