1 Alternate strategy for Y1, Y2
3 * This is (in effect) the strategy used by OCaml. The mutually recursive:
6 f x = A ; A may refer to f or g
8 g y = B ; B may refer to f or g
12 is implemented using regular, non-mutual recursion, like this (`f'` is a variable not occurring free in `A`, `B`, or `C`):
14 let rec f' g x = (let f = f' g in A)
15 in let rec g y = (let f = f' g in B)
18 or, expanded into the form we've been working with:
20 let f' = Y (\f' g x. (\f. A) (f' g)) in
21 let g = Y (\g y. (\f. B) (f' g)) in