bug in kernel_on() in "matrix2.pyx"

[sagetrac-GeorgSWeber]

sage: V = span([[1/7,0,0] ,[0,1,0]], ZZ); V
Free module of degree 3 and rank 2 over Integer Ring
Echelon basis matrix:
[1/7   0   0]
[  0   1   0]
sage: T = matrix(ZZ,3,[1,0,0,0,0,0,0,0,0]); T
[1 0 0]
[0 0 0]
[0 0 0]
sage: W = T.kernel_on(V); W.basis()
[
(0, 1, 0)
]
sage: W.is_submodule(V)
False

This is surprising, isn't it? (Patch comes up in a minute, but I need to create the ticket first.)

Component: linear algebra

Author: Georg S. Weber

Reviewer: William Stein

Merged: sage-4.5.2.alpha0

Issue created by migration from https://trac.sagemath.org/ticket/9425

[sagetrac-GeorgSWeber]

Attachment: trac_9425_kernel_on.patch.gz

created against the older Sage-4.4.2, but that shouldn't matter

[sagetrac-GeorgSWeber]

Author: Georg S. Weber

[williamstein]

comment:2

Looks good to me. Thanks!

[qed777]

Merged: sage-4.5.2.alpha0

[qed777]

Reviewer: William Stein