order.rkt

#lang lazy
; put racket instead of lazy in the line above to make it less lazy

(struct zero () #:transparent)
(struct succ (pred) #:transparent)

(define one (succ (zero)))
(define two (succ one))
(define (inf) (succ (inf)))

(define (<= a b)
  (cond 
    [(zero? a) #t]
    [(zero? b) #f]
    [else (<= (succ-pred a) (succ-pred b))]))

#|
can try these in the REPL...

(<= one two)
(<= two one)
(<= two (inf))
(<= (inf) two)
(<= (inf) (inf))
|#