PEP 242 Released
Konrad Hinsen
hinsen at cnrs-orleans.fr
Thu Mar 22 10:03:54 EST 2001
"Paul F. Dubois" <paul at pfdubois.com> writes:
> PEP: 242
> Title: Numeric Kinds
Looks good overall. I am just wondering how much of a problem this is
in real life - I have used Python on several platforms, and on all of
them a float was an IEEE double.
> Coercion
>
> In an expression, coercion between different kinds is to the
> greater kind. For this purpose, all complex kinds are "greater
> than" all floating-point kinds, and all floating-point kinds are
> "greater than" all integer kinds.
This might lead to a loss of precision when combining a high-precision
float with a low-precision complex number. It would be better to use a
complex type whose precision is determined by coercion between the
real part of the complex number and the other float.
> Open Issues
>
> The assertion that a decimal literal means a binary floating-point
> value of the largest available kind is in conflict with other
> proposals about Python's numeric model. This PEP asserts that
> these other proposals are wrong and that part of them should not
> be implemented.
Do you mean Moshe Zadka's proposal for rational numbers and
corresponding literals? One could reconcile both proposals by deciding
that Moshe's rationals are equivalent to infinite-precision floats.
Then literals would always be rationals and the kind objects would
convert to the desired float type.
--
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