Pythonで継続渡し(CPS)

fact.py

def add(x, y, k):
    k(x + y)

def subtract(x, y, k):
    k(x - y)

def multiply(x, y, k):
    k(x * y)

def isequivalent(x, y, k):
    k(x == y)

def fact(n, k):
    isequivalent(n, 0, \
                 lambda u : \
                 k(1) \
                 if u \
                 else subtract(n, 1, \
                               lambda v :
                               fact(v, \
                                    lambda w :
                                    multiply(n, w, k))))

leaf-count.py

def leaf_count(tree, cont):
    if isinstance(tree, list):
        if tree == []:
            cont(0)
        else:
            leaf_count(tree[0],\
                       lambda n :\
                       leaf_count(tree[1:],\
                                  lambda m : cont(m + n)))
    else:
        cont(1)