Set iteration is broken over sets created with iterators

[sagetrac-anakha]

This works:

sage: list(Set([1, 2, 3, 4, 5]))
[1, 2, 3, 4, 5]

But this doesn't:

sage: list(Set(iter([1, 2, 3, 4, 5])))
[]

Basically Set makes a Set_object() out of it and Set_object is really not prepared to deal with an iterator. I glanced over the code and did find an obvious solution.

Component: misc

Issue created by migration from https://trac.sagemath.org/ticket/3933

[sagetrac-anakha]

comment:1

The examples should read

sage: list(Set([1, 2, 3, 4, 5]))
[1, 2, 3, 4, 5]

and

sage: list(Set(iter([1, 2, 3, 4, 5])))
[]

[rlmill]

comment:3

amusingly:

sage: list(Set(iter([1, 2, 3, 4, 5])))
[]
sage: list(Set(set(iter([1, 2, 3, 4, 5]))))
[1, 2, 3, 4, 5]

[rlmill]

comment:4

Also, I was worried about giving it an infinite iterator, but it seems Python is happy to shoot itself in the foot:

sage: set(Primes())
<wait approximately forever for nothing to happen>

[rlmill]

comment:5

Attachment: trac-3933.patch.gz

[sagetrac-abergeron]

comment:6

This works and passes tests. So I give it a positive review.

[sagetrac-mabshoff]

comment:7

Merged in Sage 3.3.alpha3