Carp/core/Tuples.carp

(deftype (Pair a b) [a a b b])

(defmodule PairRef
  (defn = [p1 p2]
    (and (= (Pair.a p1) (Pair.a p2))
         (= (Pair.b p1) (Pair.b p2))))
  (implements = PairRef.=)

  (defn < [p1 p2]
    (if (= (Pair.a p1) (Pair.a p2))
      (< (Pair.b p1) (Pair.b p2))
      (< (Pair.a p1) (Pair.a p2))))
  (implements < PairRef.<)

  (defn > [p1 p2]
    (PairRef.< p2 p1)))
  (implements > PairRef.>)

(defmodule Pair
  (defn init-from-refs [r1 r2]
    (Pair.init @r1 @r2))

  (defn = [p1 p2]
    (and (= (Pair.a &p1) (Pair.a &p2))
         (= (Pair.b &p1) (Pair.b &p2))))
  (implements = Pair.=)

  (defn < [p1 p2]
    (PairRef.< &p1 &p2))
  (implements < Pair.<)

  (defn > [p1 p2]
    (PairRef.> &p1 &p2))
  (implements > Pair.>)

  (doc reverse "reverses a `Pair` `p` such that its first member is its second member and vice versa.")
  (defn reverse [p]
    (Pair.init @(Pair.b p) @(Pair.a p)))

  (doc zero "return default values of the type inside `Pair`")
  (defn zero []
      (Pair.init (zero) (zero)))
)