[Python-Dev] Fixed-decimal types

[Jim Fulton]

Jim Fulton wrote:
> 
> Guido van Rossum 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).
> 
> I'd be inclined to start by doing some research to see if some standard
> (SQL?) defines this somewhere.  It would be nice if someone has already
> done the requirements work for us. :)

Here is what the book "SQL-99 Complete, Really" says that the SQL
standard says:

  - for addition and subtraction of two "exact" (fixed-decimal)
    numbers, the result has the maximum of the scales.

  - for multiplication of two "exact" (fixed-decimal)
    numbers, the result has the sum of the scales.

  - punts on division

  - for addition, subtraction, multiplication or division
    between "exact" (fixed point) and "approximate" (floating point)
    yields an approximate result.  This means that fixed-decimal
    coerces to float.

I'm curious to see who else chips in with examples from other systems.

Jim

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