egisatoshi

% cat anagram.egi
(define $anagram?
  (lambda [$xs $ys]
    (match ys (multiset eq)
      {[,xs #t]
       [_ #f]})))

(anagram? (between 1 31) (reverse (between 1 31)))
(anagram? (between 1 31) (reverse (between 2 32)))
% time egison -t anagram.egi

egisatoshi

Egisonプログラミングコンテスト2018問題集

パターンマッチ指向プログラミング

関数型プログラミングにおいて基本的なリスト操作関数を再帰を使わずに，単一のmatch-all式で定義できる． たとえば，map関数は以下のように定義できる．

(define $map
 (lambda [$f $xs]

egisatoshi

(take 6 (match-all primes (list integer)
          [<join _ <cons $p <cons ,(+ p 2) _>>>
           [p (+ p 2)]]))

egisatoshi

concat (matchAll (["akira", "susumu", "tamotsu", "tomo"], ["blue", "green", "red", "white"], [1, 2, 3, 4])
              as (list something, multiset something, multiset something) with
          | ([$x_1, $x_2, $x_3, $x_4], [$y_1, $y_2, $y_3, $y_4], [$z_1, $z_2, $z_3, $z_4])
          -> matchAll [(x_1, y_1, z_1), (x_2, y_2, z_2), (x_3, y_3, z_3), (x_4, y_4, z_4)]
                   as set (eq, eq, eq) with
               | (#"akira", #"blue", !#1) ::
                 (#"susumu", !#"green", !#4) ::
                 (_, #"red", #2) ::
                 (_, #"white", $n) ::
                 (#"tamotsu", _, #(n - 1)) :: _