```
;; -*- Mode: Irken -*-
;; See http://en.wikipedia.org/wiki/Fixed_point_combinator
(include "lib/core.scm")
(define (Y f)
(lambda (x)
((f (Y f)) x)))
(define (factabs fact)
(lambda (x)
(if (= x 0)
1
(* x (fact (- x 1))))))
(printn ((Y factabs) 5))
;; and http://caml.inria.fr/pub/docs/u3-ocaml/ocaml-ml.html#toc5
;; let fix f' = let g f x = f' (f f) x in (g g);;
;; let fact = fix fact' in fact 5;;
(define (Y2 f1)
;; the '^' prefix tells the compiler not to inline this function
;; which in this particular case would never terminate...
(define (^g f)
(lambda (x)
(f1 (f f) x)))
(^g ^g))
(define (fact1 fact x)
(if (= x 0)
1
(* x (fact (- x 1)))))
(printn ((Y2 fact1) 5))
```

The function ^g has type

μ(A, (A->b))->(c->d)

## No comments:

## Post a Comment