Problem 1: A Sub Abs B (100pts)

Fill in the blanks in the following function for subtracting $a$ with the absolute value of $b$, without calling abs. You may not modify any of the provided code other than the two blanks.

from operator import add, sub, mul, neg

def a_sub_abs_b(a, b):
    """Return a-abs(b), but do not call abs.

    >>> a_sub_abs_b(2, 3)
    -1
    >>> a_sub_abs_b(2, -3)
    -1
    >>> # a check that you didn't change the return statement!
    >>> import inspect, re
    >>> re.findall(r'^\s*(return .*)', inspect.getsource(a_sub_abs_b), re.M)
    ['return h(a, b)']
    """
    if b >= 0:
        h = _____
    else:
        h = _____
    return h(a, b)

Hint: You may want to use add, sub, mul and/or neg that imported from opeartor.

Here is the documentation of these operators.

Test your implementation with python3 ok -q a_sub_abs_b.

在大多数作业中，大家可以用python3 ok -q 函数名的方式来测试对应的函数，后面就不再赘述了。