[Python-Dev] Revised decimal type PEP

Aahz Maruch aahz@rahul.net
Tue, 31 Jul 2001 09:37:02 -0700 (PDT)

Michael McLay wrote:
> Those were easy.  How would the following be interpreted?
>    decimal 3.404, 2)
>    decimal 3.405, 2)
>    decimal(3.39999, 2)
>  [...]
> For addition, subtraction, and multiplication the results would be
> exact with no rounding of the results.  Calculations that include
> division the number of digits in a non-terminating result will have to
> be explicitly set.  Would it make sense for this to be definedby the
> numbers used in the calculation?  Could this be set in the module or
> could it be global for the application?

This is why Cowlishaw et al require a full context for all operations.
At one point I tried implementing things with the context being
contained in the number rather than "global" (which actually means
thread-global, but I'm probably punting on *that* bit for the moment),
but Tim Peters persuaded me that sticking with the spec was the Right
Thing until *after* the spec was fully implemented.

After seeing the mess generated by PEP-238, I'm fervently in favor of
sticking with external specs whenever possible.
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