I may be quite late to the party, but we can create custom foldr using simple lambda calculus and curried function. Here is my implementation of foldr in python.
def foldr(func):
def accumulator(acc):
def listFunc(l):
if l:
x = l[0]
xs = l[1:]
return func(x)(foldr(func)(acc)(xs))
else:
return acc
return listFunc
return accumulator
def curried_add(x):
def inner(y):
return x + y
return inner
def curried_mult(x):
def inner(y):
return x * y
return inner
print foldr(curried_add)(0)(range(1, 6))
print foldr(curried_mult)(1)(range(1, 6))
Even though the implementation is recursive (might be slow), it will print the values 15 and 120 respectively