On 2/25/2013 6:53 PM, Greg Ewing wrote:
Barry Warsaw wrote:
>>> Colors = make('Colors', 'red green blue'.split())
>>> Animals = make('Animals', 'ant bee cat'.split())
>>> Colors.green == Animals.bee
The currently suggested solution to that seems to be to
make comparison non-transitive, so that Colors.green == 1
and Animals.bee == 1 but Colors.green != Animals.bee.
And then hope that this does not create a quantum black
hole that sucks us all into a logical singularity...
But it will;-).
To repeat myself, transitivity of equality is basic to thought, logic,
and sets and we should not deliver Python with it broken. (The
non-reflexivity of NAN is a different issue, but NANs are intentionally
insane.)
Decimal(0) == 0 == 0.0 != Decimal(0) != Fraction(0) == 0
was a problem we finally fixed by making integer-valued decimals
compare equal to the same valued floats and fractions. In 3.3:
>>> from decimal import Decimal as D
>>> from fractions import Fraction as F
>>> 0 == 0.0 == D(0) == F(0)
True
http://bugs.python.org/issue4087
http://bugs.python.org/issue4090
explain the practical problems. We should NOT knowingly go down this
road again. If color and animal are isolated from each other, they
should each be isolated from everything, including int.
--
Terry Jan Reedy
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