test_traverse.py 文件源码

def test_expr_fns():
    from sympy.strategies.rl import rebuild
    from sympy import Add
    x, y = map(Symbol, 'xy')
    expr = x + y**3
    e = bottom_up(lambda x: x + 1, expr_fns)(expr)
    b = bottom_up(lambda x: Basic.__new__(Add, x, 1), basic_fns)(expr)

    assert rebuild(b) == e