Hello,
2011/2/2 Frédéric Chapoton <[email protected]>:
> Here is a little more detail, a reduced example, coming from the
> problem above.
>
> sage: kiki
> {B[[1, 0, 1, 1, 0, 1, 0, 1, 0, 0]] + B[[1, 0, 1, 1, 1, 0, 0, 1, 0, 0]]
> + B[[1, 0, 1, 1, 0, 1, 1, 0, 0, 0]] + B[[1, 0, 1, 1, 1, 0, 1, 0, 0,
> 0]] + B[[1, 0, 1, 1, 1, 1, 0, 0, 0, 0]], B[[1, 0, 1, 1, 0, 1, 0, 1, 0,
> 0]] + B[[1, 0, 1, 1, 0, 1, 1, 0, 0, 0]] + B[[1, 0, 1, 1, 1, 0, 0, 1,
> 0, 0]] + B[[1, 0, 1, 1, 1, 0, 1, 0, 0, 0]] + B[[1, 0, 1, 1, 1, 1, 0,
> 0, 0, 0]]}
> sage: kiki.cardinality()
> 2
> sage: kiki[0]==kiki[1]
> True
> sage: kiki[0]-kiki[1]
> 0
>
> so these 2 linear combinations differ only by their order.
My guess is that it is an issue with the hashing of the elements of
"kiki" -- perhaps the hash is based on an ordering? What types of
objects are they? Here's a way to reproduce similar behavior:
class Foo(object):
def __init__(self, value):
self.value = value
def __eq__(self, other):
return isinstance(other, Foo) and self.value == other.value
def __hash__(self):
import random
return random.randint(0,10000)
def __repr__(self):
return repr(self.value)
sage: a = Foo(1)
sage: b = Foo(1)
sage: a == b
True
sage: Set([a,b])
{1, 1}
sage: mySet = Set([a,b])
sage: Set([len([v for v in mySet if v==u]) for u in mySet])
{2}
--Mike
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