Sorry; the function I wrote is wrong:
def restrict_right(M,W):
return (M.transpose().restrict(W)).transpose()
On Dec 3, 11:23 pm, adrian <nihilalienumcr...@gmail.com> wrote:
> The following code breakes with
> ArithmeticError: subspace is not invariant under matrix
>
> since sage assumes that vectors are left vectors. However there is no
> restrict_right nor restrict_left methods.
>
> V=VectorSpace(QQ,3)
> W=V.subspace_with_basis([[0,1,0],[1,1,0]])
> M=matrix(ZZ,3,3,[1,0,1,1,0,0,0,0,1])
> show(W)
> show(M)
> show(M.restrict(W))
>
> The fix is simple
> def restrict_right(W):
> return (W.transpose().restrict(W)).transpose()
>
> I guess the same assumptions are made for restrict_domain and
> restrict_codomain
>
> V=VectorSpace(QQ,3)
> W=V.subspace_with_basis([[0,1,0],[1,1,0]])
> M=matrix(ZZ,3,3,[1,0,1,1,0,0,0,0,1])
>
> show(W)
> show(M)
> show(M.restrict(W))
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