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15836 BasisMatroid.circuits() returns a malformed SetSystem when called on the empty matroid Rudi Rudi "The following produces an error:
{{{
from sage.matroids.advanced import *
M=Basismatroid(groundset=[], rank =0)
for C in M.circuits(): print C
}}}
Also, len(M.circuits()) is reported to be 1, whereas len(M.cocircuits()) is 0 and the latter is not malformed.
It is a bit of a theological issue, but I think we agree that the matroid on zero elements has circuits nor cocircuits:
in general a matroid of rank 0 on k elements has k circuits and no cocircuits.
So I want to make sure that M.circuits() returns that empty SetSystem (easy enough) but I also want to find out how it is possible that the SetSystem becomes malformed in this case.
" defect closed minor sage-6.2 matroid theory fixed stefan yomcat Rudi Pendavingh Jayant Apte N/A 329566023aaef2d2f534bfe7cf1753052055b335 329566023aaef2d2f534bfe7cf1753052055b335