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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