[Python-Dev] Fixed-decimal types

[Andy Robinson]

--- Guido van Rossum <guido@CNRI.Reston.VA.US> wrote:
> What would be scale of the product of two
> fixed-decimal numbers?
> E.g. is 2.00L * 2.00L equal to 4.0000L, or equal to
> 4.00L?  There are
> arguments for either.  Same question for division
> (harder, I think).
Most commonly one is trying to avoid rounding errors
when dealing with money - a few cents rounding error
tends to result in a few billable hours with the
accountants at the end of the year!

SQL dialects and type-safe languages would make you
specify the precision of the variable to be assigned,
so the issue does not arise for other languages.  

For the work I do, simply taking the precision of the
most precise input (4.00L)would do the trick, but your
answer (4.0000L) is purer.  We should provide a
rounding function, and in practice anyone using such a
function would round (or floor, or ceiling) to get to
the desired precision immediately.

I'm not sure on division either but I'm sure there are
precedents to look at.

On the subject of adding new types to the standard
library, what are the plans on dates and times?  Would
a cut-down mxDateTime ever be considered?  It is fully
Open Source (unlike mxODBC) and was designed for the
DBAPI.

Regards,

Andy

=====
Andy Robinson
Robinson Analytics Ltd.
------------------
My opinions are the official policy of Robinson Analytics Ltd.
They just vary from day to day.

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