#13695: Subsets(1)[x] behaves strangely for x in SR
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Reporter: ppurka | Owner: sage-combinat
Type: defect | Status: new
Priority: major | Milestone: sage-5.5
Component: combinatorics | Keywords:
Work issues: | Report Upstream: N/A
Reviewers: | Authors:
Merged in: | Dependencies:
Stopgaps: |
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This bug is from the
[https://spreadsheets.google.com/pub?key=pCwvGVwSMxTzT6E2xNdo5fA sage
notebook bug report page].
{{{
A = Subsets(1);
k=var('k')
sum((-1)^(A[k].cardinality()),k,0,A.cardinality()-1)
Sage gives me 2 as an answer, while it should be 0.
}}}
The problem seems to be in `sage.combinat.subset.Subsets_s.unrank` which
does not check whether the arguments it receives are integers or not. So,
doing something like the title gives the empty set and so we get 2 as the
answer above.
{{{
sage: Subsets(1)[x]
{}
}}}
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/13695>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
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