test_euler.py 文件源码

def test_euler_interface():
    x = Function('x')
    y = Symbol('y')
    t = Symbol('t')
    raises(TypeError, lambda: euler())
    raises(TypeError, lambda: euler(D(x(t), t)*y(t), [x(t), y]))
    raises(ValueError, lambda: euler(D(x(t), t)*x(y), [x(t), x(y)]))
    raises(TypeError, lambda: euler(D(x(t), t)**2, x(0)))
    assert euler(D(x(t), t)**2/2, {x(t)}) == [Eq(-D(x(t), t, t))]
    assert euler(D(x(t), t)**2/2, x(t), {t}) == [Eq(-D(x(t), t, t))]