Functional
----------

Utils for functional programming.

.. py:function:: pydu.functional.compose(*funcs)

    Compose all functions. The previous function must accept one argument,
    which is the output of the next function. The last function can accept
    any args and kwargs. 
    
    compose(f1, f2, f3)(\*x) is same to f1(f2(f3(\*x))).

    >>> from pydu.functional import compose
    >>> def f1(a):
    ...     return a+1
    ...
    >>> def f2(a, b=2):
    ...     return a+b
    ...
    >>> compose(f1, f2)(1, b=3)
    5