On 10/29/2012 07:19 AM, John Collins wrote: > <snip> >> Equality. > Right, in a 1,0 sense. >> Because of rounding errors this is a dangerous operation for floating >> point >> numbers: >>>>> print 1.0 == .1 + .1 + .1 + .1 + .1 + .1 + .1 + .1 + .1 + .1 >> False > I take it that is because binary for .1 is a repeating sequence, yes?
Yes. Since it cannot be represented exactly, you get a quantization error. > <snip> >> As you correctly observed crospoints() uses only +-*/ and ==, so you can >> feed it every type that supports these operations (this is called "duck >> typing"). For example: > >>>>> from fractions import Fraction >>>>> from crosspoint import crosspoint >>>>> crosspoint(Fraction(0, 1), Fraction(1, 3), Fraction(1, 1), >>>>> Fraction(1, >> 3), Fraction(5, 7), Fraction(0, 1), Fraction(5, 7), Fraction(1, 1)) >> (Fraction(5, 7), Fraction(1, 3)) >>>>> p = crosspoint(Fraction(0, 1), Fraction(1, 3), Fraction(1, 1), >> Fraction(1, 3), Fraction(5, 7), Fraction(0, 1), Fraction(5, 7), >> Fraction(1, >> 1)) >>>>> print "%s, %s" % p >> 5/7, 1/3 >> >> Yay, infinite precision ;) > You just lost me. If you don't use any transcendental functions, then a fraction has no quantization error. It's totally precise. -- DaveA _______________________________________________ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
