(define zero (lambda (f) (lambda (x) x)))

(define (add-1 n)

  (lambda (f) (lambda (x) (f ((n f) x)))))

(define one (lambda (f) (lambda (x) (f x))))

(define (plus a b) (lambda (f) (lambda (x) ((b f) ((a f) x)))))

(define (test n int)

  (equal? int ((n (lambda (x) (+ x 1))) 0)))
' test result

> (test zero 0)

#t

> (test one 1)

#t

> (test (add-1 zero) 1)

#t

> (test (plus zero zero) 0)

#t

> (test (plus zero one) 1)

#t

> (test (plus one one) 2)

#t

> (test (plus one (plus one one)) 3)

#t

>