def tridiag():
m = Matrix(TRI_DIAGONAL)
a = [0] # a0 is not used but must be present
a.extend(m.diag(-1))
b = m.diag(0)
c = m.diag(+1)
return a, b, c
def test_diag():
m = Matrix(DIAG)
assert m.diag(0) == [1, 2, 3, 4]
assert m.diag(1) == [2, 3, 4]
assert m.diag(2) == [5, 6]
assert m.diag(3) == [7]
assert m.diag(4) == []
assert m.diag(-1) == [5, 4, 3]
assert m.diag(-2) == [7, 6]
assert m.diag(-3) == [8]
assert m.diag(-4) == []
