@sig(["a"]/ H[(Eq, "a")] >> ["a"] >> ["a"])
def intersect(xs, ys):
    """
    intersect :: Eq a => [a] -> [a] -> [a]

    The intersect function takes the list intersection of two lists.  It is a
    special case of intersectBy, which allows the programmer to supply their
    own equality test. If the element is found in both the first and the second
    list, the element from the first list will be used.
    """
    raise NotImplementedError()


#=============================================================================#
## Ordered lists
dataset/ETHPy150Open billpmurphy/hask/hask/Data/List.py/intersect/swapped operands of `/`