(require (lib "defmacro.ss"))

(define y-combinator
  (λ (x)
    ((λ (p) (x (λ (n) ((p p) n))))
     (λ (p) (x (λ (n) ((p p) n)))))))

(define-macro y-lambda
  (λ (self proc)
    (let ((self-symbol (car self)))
      `(y-combinator (λ (,self-symbol) ,proc)))))

((y-lambda (self) (λ (n) (if (zero? n) 1 (* n (self (- n 1)))))) 5) ; 120