In article <[EMAIL PROTECTED]>, "Hendrik van Rooyen" <[EMAIL PROTECTED]> writes: |> |> Ok I will throw in a skewed ball at this point - use integer arithmetic, |> and work in tenths of cents or pennies or whatever, and don't be too |> lazy to do your own print formatting...
If anyone is interested in doing this, here are a few notes on some of the non-trivial aspects. Please feel free if you want to contact me for more information. All numbers are held as (precision, value). Precision is the number of digits after the decimal point (a small, often constant, integer) and the value is held as an integer. It would be possible to have a separate subclass or context for every precision (like Decimal), but that would be an unnecessary complication. +, - and % return a precision that is the maximum of their input precisions, and // returns a precision of 0. * returns a precision that is the sum of its input precisions. / returns a floating-point number! There is a divide function that takes a divisor, dividend and output precision. It also takes a rounding rule as an optional argument (up, down, in, out, conventional nearest or IEEE 754R nearest). There is a precision conversion function that takes a value and output precision, and a rounding rule as an optional argument. There is a conversion function that takes a string or floating-point number and output precision, and a rounding rule as an optional argument. It raises an exception if a 1 ULP change in the floating- point number would give a different answer; this is needed to make certain operations reliable. The default formatting does the obvious thing :-) Er, that's about it .... Regards, Nick Maclaren. -- http://mail.python.org/mailman/listinfo/python-list
