The following curious bug came up during work on ticket #12233. For some reason, if one creates a 2x2 integer matrix directly using the constructor then it is possible to tell it to be immutable; but if one creates one via arithmetic operations then calling "set_immutable" on it fails. Here's an example:
sage: from sage.matrix.matrix_integer_2x2 import Matrix_integer_2x2 as mi2x2 sage: M2Z = MatrixSpace(ZZ,2) sage: mi2x2(M2Z, [1,0,0,1]) sage: x=mi2x2(M2Z, [1,0,0,1], false, false) sage: y=mi2x2(M2Z, [1,0,0,1], false, false) sage: type(x) <type 'sage.matrix.matrix_integer_2x2.Matrix_integer_2x2'> sage: z = x*y sage: type(z) <type 'sage.matrix.matrix_integer_2x2.Matrix_integer_2x2'> sage: x.set_immutable() # ok sage: z.set_immutable() # error [...] AttributeError: 'NoneType' object has no attribute 'set_immutable' (Many thanks to Timo Kluck for clarifying the problem and finding this example.) Does anyone have any idea what's going on here, and if so how to fix it? Regards, David -- You received this message because you are subscribed to the Google Groups "sage-devel" group. To post to this group, send email to sage-devel@googlegroups.com. To unsubscribe from this group, send email to sage-devel+unsubscr...@googlegroups.com. Visit this group at http://groups.google.com/group/sage-devel?hl=en.
