On Wed, 25 Jun 2014 14:12:31 -0700, Maciej Dziardziel wrote:
> Floating points values use finite amount of memory, and cannot
> accurately represent infinite amount of numbers, they are only
> approximations. This is limitation of float type and applies to any
> languages that uses types supported directly by cpu. To deal with it you
> can either use decimal.Decimal type that operates using decimal system
> and saves you from such surprises
That's a myth. decimal.Decimal *is* a floating point value, and is
subject to *exactly* the same surprises as binary floats, except for one:
which Decimal, you can guarantee that any decimal string you enter will
appear exactly the same (up to the limit of the current precision).
For example:
py> x = Decimal(1)/Decimal(23)
py> x
Decimal('0.04347826086956521739130434783')
py> x*23 == 1
True
py> sum( [x]*23 ) == 1 # Surprise!
False
py> (Decimal(19)/Decimal(17))*Decimal(17) == 19 # Surprise!
False
--
Steven
--
https://mail.python.org/mailman/listinfo/python-list
