Random832 <random...@fastmail.com>: > On Sat, Jul 16, 2016, at 03:27, Chris Angelico wrote: >> Will an "Exact" non-integer be stored as Decimal or >> Fraction? How do you know? They have vastly different semantics, and >> you should be able to choose. > > Er, the point is for them to _not_ have different semantics. A decimal > storage format would simply be an optimization for a fraction whose > denominator is a power of 10 (or of 2 and 5) > > The semantics of the current Decimal class are those of an inexact > number.
The most common use for Python's Decimal class is *exact* amounts of currency. The exactness of a number in Scheme is just a flag. You can force exactness of a number literal with the #e or #i prefix: (exact? #e1.2e-7) ==> #t # 1.2e-7 exactly (exact? #i7) ==> #f # approximately 7 Marko -- https://mail.python.org/mailman/listinfo/python-list
