need_y_combinator.coffee

need_y_combinator.coffee

# normal factorial
factorial = (x) ->
  if x == 1 then return 1
  return x * factorial(x - 1)
console.log factorial(6) #720


# new factorial that doesn't reference itself
factorialGenerator = (fac) ->
  (x) ->
    if x == 1 then return 1
    return x * fac(x - 1)

# imagine the function Y exists
# what function Y would make this work equal 720?
console.log Y(factorialGenerator)(7) #720