I'm seeing a change in error messages when multiplying matrices over
incompatible rings.
This is current behavior for just the elements of the base rings.
{{{
sage: QQ(45/67)*GF(7)(3)
---------------------------------------------------------------------------
TypeError Traceback (most recent call
last)
/home/sage/dev/devel/sage-main/<ipython console> in <module>()
/sage/dev/local/lib/python2.6/site-packages/sage/structure/element.so
in sage.structure.element.RingElement.__mul__ (sage/structure/
element.c:12061)()
/sage/dev/local/lib/python2.6/site-packages/sage/structure/coerce.so
in sage.structure.coerce.CoercionModel_cache_maps.bin_op (sage/
structure/coerce.c:7327)()
TypeError: unsupported operand parent(s) for '*': 'Rational Field' and
'Finite Field of size 7'
}}}
Good. But now, for matrices over the same base rings, the traceback
is longer and concludes complaining about not having an inverse of an
element (maybe in GF(7)?). Three months ago, a matrix product like
this would have yielded a traceback and error message pretty much just
like what happens above for plain elements.
Any guesses on what has changed? This looks to me like a step
backwards, so I wonder if something more fundamental is wrong?
{{{
sage: sage: W = matrix(QQ, 1, 2, [3, 4])
sage: sage: V = matrix(GF(7), 2, 1, [2, 5])
sage: sage: W*V
---------------------------------------------------------------------------
ZeroDivisionError Traceback (most recent call
last)
/home/sage/dev/devel/sage-main/<ipython console> in <module>()
/sage/dev/local/lib/python2.6/site-packages/sage/structure/element.so
in sage.structure.element.Matrix.__mul__ (sage/structure/element.c:
15876)()
/sage/dev/local/lib/python2.6/site-packages/sage/structure/coerce.so
in sage.structure.coerce.CoercionModel_cache_maps.bin_op (sage/
structure/coerce.c:6368)()
/sage/dev/local/lib/python2.6/site-packages/sage/matrix/action.so in
sage.matrix.action.MatrixMatrixAction._call_ (sage/matrix/action.c:
2742)()
/sage/dev/local/lib/python2.6/site-packages/sage/matrix/
matrix_rational_dense.so in
sage.matrix.matrix_rational_dense.Matrix_rational_dense.change_ring
(sage/matrix/matrix_rational_dense.c:13867)()
/sage/dev/local/lib/python2.6/site-packages/sage/structure/element.so
in sage.structure.element.RingElement.__div__ (sage/structure/
element.c:12722)()
/sage/dev/local/lib/python2.6/site-packages/sage/structure/coerce.so
in sage.structure.coerce.CoercionModel_cache_maps.bin_op (sage/
structure/coerce.c:6426)()
/sage/dev/local/lib/python2.6/site-packages/sage/structure/element.so
in sage.structure.element.RingElement.__div__ (sage/structure/
element.c:12696)()
/sage/dev/local/lib/python2.6/site-packages/sage/rings/finite_rings/
integer_mod.so in
sage.rings.finite_rings.integer_mod.IntegerMod_int._div_ (sage/rings/
finite_rings/integer_mod.c:19384)()
ZeroDivisionError: Inverse does not exist.
}}}
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