gistfile1.scm

(define $maybe
  (lambda [$a]
    (matcher {
      ;; <primitive-pp> 
      [,$val [a] {[$tgt 
        (match [val tgt] [(maybe a) (maybe a)] {
          [[<just $x> <just ,x>] {[x]}]
          [[<nothing> <nothing>] {[]}]
          [_ {}]})]}]
      ;; <primitive-dp> 
      [<just $> [a] {[<Just $x> {[x]}] [_ {}]}]
      [<nothing> [] {[<Nothing> {[]}] [_ {}]}]})))


;; <OK> patterns
(test "------------")
(test (match <Just 5> (maybe integer) {[,<Just 5> <OK>] [_ <KO>]}))
(test (match <Nothing> (maybe integer) {[,<Nothing> <OK>] [_ <KO>]}))
(test (match <Just 10> (maybe integer) {[<just ,10> <OK>] [_ <KO>]}))
(test (match <Nothing> (maybe integer) {[<nothing> <OK>] [_ <KO>]}))

(test (match <Just {1 2 3}> (maybe (list integer)) {[<just <cons ,1 _>> <OK>] [_ <KO>]}))
(test (match <Just {2 1 3}> (maybe (multiset integer)) {[<just <cons ,1 _>> <OK>] [_ <KO>]}))

;; <KO> patterns
(test "------------")
(test (match <Just 5> (maybe integer) {[,<Nothing> <OK>] [_ <KO>]}))
(test (match <Nothing> (maybe integer) {[,<Just 10> <OK>] [_ <KO>]}))
(test (match <Just 10> (maybe integer) {[<just ,8> <OK>] [_ <KO>]}))
(test (match <Just 15> (maybe integer) {[<nothing> <OK>] [_ <KO>]}))
(test (match <Nothing> (maybe integer) {[<just _> <OK>] [_ <KO>]}))

(test (match <Just {1 2 3}> (maybe (list integer)) {[<just <cons ,3 _>> <OK>] [_ <KO>]}))
(test (match <Just {2 1 3}> (maybe (multiset integer)) {[<just <nil>> <OK>] [_ <KO>]}))