**Eight matrices inside the list J:**

J := [Matrix([[1, 0], [0, 1]]), Matrix([[0, -I], [-I, 0]]), Matrix([[0, -1], [1, 0]]), Matrix([[-I, 0], [0, I]]), Matrix([[-1, 0], [0, -1]]), Matrix([[0, I], [I, 0]]), Matrix([[0, 1], [-1, 0]]), Matrix([[I, 0], [0, -I]])];

**Function member identifies J[2] as a member of J and returns its position in j:**

member(J[2], J, 'j'); j;

**Matrix multiplication inside a loop does not have a matrix type:**

for i to 1 do for j to 2 do a := J[i].J[j]; member(a, J, 'k'); print(i, j, k, a, whattype(a)) end do end do;

**Has anyone any ideia of what is going on?**