[Python-Dev] calculator module

[Gareth McCaughan]

On Wednesday 2004-03-10 at 15:03, Guido van Rossum wrote:

> Maybe this project should use decimal arithmetic throughout?  After all,
> student calculators use decimal, and explaining binary is a source of
> unneeded confusion during student's early steps.  It would also be a
> good way to get the Decimal numbers project integrated into core
> Python.

Decimal doesn't currently support the functions (cos, exp, log, ...)
currently in the "math" module. Making Raymond's proposal work
with Decimal objects would require implementing all those things
for Decimals. That's appreciably more work than implementing just
the new functions for doubles.

Further, I'd argue that since Decimal can work with numbers
of arbitrary precision, an implementation of (say) exp that
works on Decimals ought to work with something like full
precision, unless it's *only* intended for casual use. Writing
implementations of all these things would be a considerable
amount of work.

Doing everything with Decimals would also reduce the utility[1]
of these functions for people who want to do something other
than interactive calculations with them, at least for as long
as such people continue to be mostly using ordinary Python
floats. I'd guess that that's approximately for ever.

    [1] Perhaps only the perceived utility, since there are
        conversions to and from the Decimal type.

To my mind, the loss isn't worth the gain.

-- 
g