For instance, `fac 0 ~~> 1`, `fac 1 ~~> 1`, `fac 2 ~~> 2`, `fac 3 ~~>
6`, and `fac 4 ~~> 24`.
- let true = \then else. then in
- let false = \then else. else in
- let iszero = \n. n (\x. false) true in
- let pred = \n f z. n (\u v. v (u f)) (K z) I in
- let succ = \n f z. f (n f z) in
- let add = \n m .n succ m in
- let mult = \n m.n(add m)0 in
- let Y = \h . (\f . h (f f)) (\f . h (f f)) in
-
- let fac = ... in
-
- fac 4
+ let true = \then else. then in
+ let false = \then else. else in
+ let iszero = \n. n (\x. false) true in
+ let pred = \n f z. n (\u v. v (u f)) (K z) I in
+ let succ = \n f z. f (n f z) in
+ let add = \n m .n succ m in
+ let mult = \n m.n(add m)0 in
+ let Y = \h . (\f . h (f f)) (\f . h (f f)) in
+
+ let fac = ... in
+
+ fac 4
## Arithmetic infinity? ##