test_matexpr.py 文件源码

def test_matrixelement_diff():
    dexpr = diff((D*w)[k,0], w[p,0])

    assert w[k, p].diff(w[k, p]) == 1
    assert w[k, p].diff(w[0, 0]) == KroneckerDelta(0, k)*KroneckerDelta(0, p)
    assert str(dexpr) == "Sum(KroneckerDelta(_k, p)*D[k, _k], (_k, 0, n - 1))"
    assert str(dexpr.doit()) == 'Piecewise((D[k, p], (0 <= p) & (p <= n - 1)), (0, True))'