Mark Dickinson wrote: > Using Fraction for intermediate calculations actually works perfectly > for this, since conversions from float to Fraction are exact, while > conversions from Fraction to float are correctly rounded. So if > you're using Python, you're not too bothered about efficiency, and you > want provably correctly-rounded results, why not use Fraction? > >>>> from fractions import Fraction >>>> start, stop, n = 0.0, 2.1, 7 >>>> [float(Fraction(start) + i * (Fraction(stop) - Fraction(start)) / n) >>>> [for i in range(n+1)] > [0.0, 0.3, 0.6, 0.9, 1.2, 1.5, 1.8, 2.1]
Ah, I knew it was too easy! >>> from fractions import Fraction as F >>> start, stop, n = 1, 3.1, 7 >>> [float(F(start) + i*(F(stop)-F(start))/n) for i in range(n+1)] [1.0, 1.3, 1.6, 1.9000000000000001, 2.2, 2.5, 2.8000000000000003, 3.1] >>> >>> start, stop, n = -1, 1.1, 7 >>> [float(F(start) + i*(F(stop)-F(start))/n) for i in range(n+1)] [-1.0, -0.7, -0.39999999999999997, -0.09999999999999996, 0.20000000000000004, 0.5000000000000001, 0.8, 1.1] -- Steven -- http://mail.python.org/mailman/listinfo/python-list
