prePEP: Decimal data type

Mel Wilson mwilson at the-wire.com
Sat Nov 1 18:23:41 CET 2003


In article <vq7ogq9t7t9017 at news.supernews.com>,
"John Roth" <newsgroups at jhrothjr.com> wrote:
>As I said in the response to Alex, division is the one place where
>fixed decimal gets into trouble. To repeat what I said to him,
>I'd eliminate the division operators completely, and replace them
>with a div(dividend, divisor, [resultplaces], [roundingpolicy])
>operator.

   I don't really like this, because it makes Decimals look
unlike numbers.

   But if I had to live with it, I'd probably wind up coding
things like

        factor1 = Decimal ('0d.333')    # 1/3 to 3 places
        sales_tax_rate = Decimal (7, -2)       # .07

(where '0d.333' is something I just cooked up as a
compromise between avoiding Decimal+string arithmetic and
accepting the fact that a series of digits is the best way
to express a decimal number.)

   Then the standard multiply would do what I wanted, and I
would have said, in building the factors, exactly what I
thought I was doing.

   I admit that the implementation I'm playing with doesn't
implement __div__ or __truediv__ yet .. because I can't
figure out the right way.

        Regards.        Mel.




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