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;;; Chickadee Game Toolkit
;;; Copyright (C) 2014 Ludovic Courtès <ludo@gnu.org>
;;; Copyright © 2016 David Thompson <davet@gnu.org>
;;;
;;; Chickadee is free software: you can redistribute it and/or modify
;;; it under the terms of the GNU General Public License as published
;;; by the Free Software Foundation, either version 3 of the License,
;;; or (at your option) any later version.
;;;
;;; Chickadee 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
;;; General Public License for more details.
;;;
;;; You should have received a copy of the GNU General Public License
;;; along with this program. If not, see
;;; <http://www.gnu.org/licenses/>.
(define-module (chickadee utils)
#:export (memoize
for-range))
;; Written by Ludovic Courtès. Taken from GNU Guix.
(define (memoize proc)
"Return a memoizing version of PROC."
(let ((cache (make-hash-table)))
(lambda args
(let ((results (hash-ref cache args)))
(if results
(apply values results)
(let ((results (call-with-values (lambda () (apply proc args))
list)))
(hash-set! cache args results)
(apply values results)))))))
(define-syntax for-range
(syntax-rules ()
((_ ((var end start inc)) body ...)
(let* ((s start) ; evaluate start/end only once
(e end)
(reverse? (< e s))
(start* (if reverse? e s))
(end* (if reverse? s e))
(inc* (abs inc)))
(let loop ((var start*))
(when (< var end*)
body ...
(loop (+ var inc*))))))
((_ ((var end start)) body ...)
(for-range ((var end start 1)) body ...))
((_ ((var end)) body ...)
(for-range ((var end 0 1)) body ...))
((_ ((var args ...) rest ...) body ...)
(for-range ((var args ...))
(for-range (rest ...)
body ...)))))
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