memorize.rkt

;;  zKanren: MicroKanren with Constraints and noto
;;  Copyright (C) 2017  Zaoqi

;;  This program is free software: you can redistribute it and/or modify
;;  it under the terms of the GNU Affero General Public License as published
;;  by the Free Software Foundation, either version 3 of the License, or
;;  (at your option) any later version.

;;  This program is distributed in the hope that it will be useful,
;;  but WITHOUT ANY WARRANTY; without even the implied warranty of
;;  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
;;  GNU Affero General Public License for more details.

;;  You should have received a copy of the GNU Affero General Public License
;;  along with this program.  If not, see <http://www.gnu.org/licenses/>.
#lang racket
(provide memorize)

#| (Any ... → a) → (Any ... → a) |#
(define (memorize f)
  (let ([m (make-weak-hash)])
    (λ args (hash-ref m args (λ ()
                               (let ([v (apply f args)])
                                 (hash-set! m args v)
                                 v))))))