;; In Emacs, open this file in -*- Scheme -*- mode.

;; Pairs

(def pair-make (fun (fst snd)
                    (let ((p (@block-alloc-0 2)))
                      (@block-set! p 0 fst)
                      (@block-set! p 1 snd)
                      p)))

(def pair?
     (fun (o)
          (and (@block? o) (= 0 (@block-tag o)))))

(def pair-fst
     (fun (p)
          (@block-get p 0)))

(def pair-snd
     (fun (p)
          (@block-get p 1)))

(def pair-derive=
     (fun (fst= snd=)
          (fun (p1 p2)
               (and (fst= (pair-fst p1) (pair-fst p2))
                    (snd= (pair-snd p1) (pair-snd p2))))))

(def pair-derive<
     (fun (fst< snd<)
          (fun (p1 p2)
               (or (fst< (pair-fst p1) (pair-fst p2))
                   (and (not (fst< (pair-fst p2) (pair-fst p1)))
                        (snd< (pair-snd p1) (pair-snd p2)))))))