<interactive>:2:9:
Occurs check: cannot construct the infinite type: t1 = t1 -> t0
In the first argument of `x', namely `x'
In the expression: x x
In the expression: \ x -> x x
Prelude> let y f = \x -> f f x
<interactive>:2:19:
Occurs check: cannot construct the infinite type:
t1 = t1 -> t2 -> t0
In the first argument of `f', namely `f'
In the expression: f f x
In the expression: \ x -> f f x
> (lambda (x) (x x))
#<CLOSURE <anon> (x) (x x)>
> (define (y f) (lambda (x) (f f x)))
#<unspecified>
> (define factorial (y (lambda (f n) (if (= n 0) 1 (* n (f f (- n 1)))))))
#<unspecified>
> (factorial 5)
120