Lamb of God

factorial.log

let


id = same =>
  same


const = always _ =>
  always


true = true false =>
  true


false = true false =>
  false


and = pred1 pred2 =>
  pred1 pred2 pred1


if = pred true false =>
  pred true false


inc = num succ zero =>
  succ (num succ zero)


plus = num1 num2 succ zero =>
  num1 succ (num2 succ zero)


mult = num1 num2 succ zero =>
  num1 (num2 succ) zero


exp = num1 num2 =>
  num2 num1


dec = num succ pred =>
  num (g h => h (g succ))
    (const zero)
    id


minus = num1 num2 =>
  (num2 dec) num1


zero? = num =>
  num (const false) true


leq? = num1 num2 =>
  zero? (minus num1 num2)


eq? = num1 num2 =>
  and (leq? num1 num2) (leq? num2 num1)


0 = succ zero =>
  zero


1 =
  inc 0


2 =
  plus 1 1


4 =
  mult 2 2


256 =
  exp 4 4


fac = num =>
  if (eq? num 1)
    1
    (* num (fac (dec num)))


in


fac 256