test_lseries.py 文件源码

def test_issue_5183():
    s = (x + 1/x).lseries()
    assert [si for si in s] == [1/x, x]
    assert next((x + x**2).lseries()) == x
    assert next(((1 + x)**7).lseries(x)) == 1
    assert next((sin(x + y)).series(x, n=3).lseries(y)) == x
    # it would be nice if all terms were grouped, but in the
    # following case that would mean that all the terms would have
    # to be known since, for example, every term has a constant in it.
    s = ((1 + x)**7).series(x, 1, n=None)
    assert [next(s) for i in range(2)] == [128, -448 + 448*x]