[Python-Dev] FP vs. tutorial (original) (raw)

Tim Peters tim@digicool.com
Mon, 21 May 2001 17:57:22 -0400

Let's get some errors cleared up first:

FixedPoint is not in the distribution.
There is no PEP for Decimal.
Decimal f.p. is not more accurate than binary f.p. In fact, it's provably worse (but not by much).

For the rest,

Yes, I'm serious about not including tutorial examples with platform-dependent output, unless they're explicitly meant to illustrate non-portable code.
Specific small examples notwithstanding, there is no uniformity across platforms in the last digit or so, because not even the IEEE- 754 standard requires that (while C is much sloppier than 754), and vendors generally don't implement anything better than the minimum necessary when it comes to f.p. (Sun is a notable exception).
Happy to add text explaining the existence of surprises, and providing a URL. Do the floating-point morons on Python-Dev find this one comprehensible?:

http://www.lahey.com/float.htm