#!/usr/bin/env python

def flattened(l):
    "http://caolanmcmahon.com/posts/flatten_for_python/"
    result = _flatten(l, lambda x: x)
    while type(result) == list and len(result) and callable(result[0]):
        if result[1] != []:
            yield result[1]
        result = result[0]([])
    yield result

def _flatten(l, fn, val=[]):
    "http://caolanmcmahon.com/posts/flatten_for_python/"
    if type(l) != list:
        return fn(l)
    if len(l) == 0:
        return fn(val)
    return [lambda x: _flatten(l[0], \
                               lambda y: _flatten(l[1:],fn,y), x), val]

# Preprocessor-like functions

def elideIfZero(test, insert):
    if test == 0:
        retString = ''
    else:
        retString = insert
    return retString

def testElideIfZero():
    print('0,test -> '+elideIfZero(0,'test'+','))
    print('1,test -> '+elideIfZero(1,'test'+','))

def ifZeroElse(test, ifTrue, ifFalse):
    if test == 0:
        return ifTrue
    else:
        return ifFalse

def ifElseString(test, string1, string2):
    retstr = ''
    if test:
        retstr = string1
    else:
        retstr = string2
    return retstr




def main():
    a = [1,2,3,4,[5,[6,7]]]
    print('a ',a)
    print('f(a)', flattened(a))
    print('[f(a)]', list(flattened(a)))
    return

if __name__ == "__main__":
    main()