Is there a trac-ticket for the behaviour of the code [1] for
FiniteEnumeratedSets? The __iter__ function is called twice when
creating a list (or a tuple). This shouldn't be; there is only a warning
given in the docstring of .list().
Daniel
[1] Copied from a warning in sage/categories/finite_enumerated_sets.py:
Let's take an example::
sage: class Example(Parent):
... def __init__(self):
... Parent.__init__(self, category =
FiniteEnumeratedSets())
... def __iter__(self):
... print "hello!"
... for x in [1,2,3]: yield x
sage: C = Example()
sage: list(C)
hello!
hello!
[1, 2, 3]
sage: list(C)
hello!
[1, 2, 3]
Note that ``hello!`` actually gets printed twice in
the first call to ``list(C)``. That's because of the
current (dubious) implementation of
:meth:`Parent.__len__`.
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