Hello everyone,
I think I identified a bug. It originated in two sets not being equal.
Here i will write sqrt instead of Pow(..., Rational(1, 2)) for readability.
{exp(sqrt(3/8)), exp(-sqrt(3/8)} and {exp(sqrt(2)*sqrt(3)/4),
exp(-sqrt(2)*sqrt(3/4)}
After going deep into this bug, it appears the problem lies with the
ordering function of FiniteSet.
FiniteSet seems to order improperly the first set, and this cannot do the
correct comparison.
the function 'ordered' seems to have trouble with Pow(...., Rational(1, 2))
because it works correctly when I use
Pow(...., S.Half).
Is there is a reason for this behaviour ? It seems the two mechanisms
should give the same results.
Also to be noted, the raw comparison ( < ) gives the correct result no
matter the arguments.
Here is the minimal failing test I could come up with exhibiting the
behaviour
from sympy import Pow, Rational
l = [Pow(3, Rational(1, 2)), -Pow(3, Rational(1, 2))]
assert list(ordered(tuple(l), warn=True)) == [-Pow(3, Rational(1, 2)),
Pow(3, Rational(1, 2))]
I am still trying to figure out why there is a difference, but I want to
make sure there is not some intended purpose for this.
Cheers,
Nicolas Patry
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