compose.py

def comp2(f,g):
    return lambda x: f(g(x))
def comp(*fs):
    return reduce(comp2, fs)
def reduce(reducing_function, fs, initial_value=None):
    fs = iter(fs)
    v = fs.next() if initial_value is None else initial_value
    for f in fs:
        v = reducing_function(v, f)
    return v

def inc(x):
    return x + 1
def double(x):
    return x * 2
def droot(x):
    while (len(str(x))>1):
        x = sum(map(int, str(x)))
    return x

def droot_(x):
    while (len(str(x))>1):
        x = sum(map(int, str(x)))
    return x