bug in pattern avoiding permutations

[jbandlow]

The following behavior is clearly bad:

sage: [p for p in Permutations(4,avoiding=[2,3,1]) if p.has_pattern([2,3,1])]               
[[2, 3, 1, 4], [4, 2, 3, 1]]

Similar behavior occurs when avoiding [1,3,2], [2,1,3], and [3,1,2].

CC: @jbandlow @sagetrac-sage-combinat

Component: combinatorics

Keywords: pattern avoiding permutations

Issue created by migration from https://trac.sagemath.org/ticket/4895

[jbandlow]

comment:2

Attachment: 4895.patch.gz

The problem was a simple typo in an initial condition (combined with a bunch of doctests that tested for incorrect behavior). Warning: I've been travelling and not had an opportunity to upgrade sage recently, so this patch is based off 3.2.1. I don't expect this to be a problem, but if the patch does not apply, let me know and I will fix it as soon as possible.

[mwhansen]

comment:3

Nice work Jason.

[sagetrac-mabshoff]

comment:4

Merged in Sage 3.3.alpha2.

Cheers,

Michael