[[tags: egg]]

== memoize

[[toc:]]

=== Description

Memoize is a CHICKEN Scheme egg that provides procedure [[https://en.wikipedia.org/wiki/Memoization|memoization]].

=== Author

[[/users/arthurmaciel|Arthur Maciel]]

=== Requirements

Requires [[srfi-69]] egg.

=== Documentation

<procedure>(memoize PROC #!optional LIMIT)</procedure>
Memoizes procedure {{PROC}}. {{LIMIT}} is an integer optionally set to avoid excessive memory usage.

==== Examples
<enscript highlight="scheme">
(use memoize)

;; Factorial - Tail-call optimization version
(define (fact x)
  (let loop ((x x) (acc 1))
    (if (= x 0)
	acc
	(loop (- x 1) (* x acc)))))

(time (fact 10000000))
; => 3.011s CPU time, 0.071s GC time (major), 16 mutations, 104/27101 GCs (major/minor)


(define memo-fact (memoize fact))

;; First call
(time (memo-fact 10000000))
; => 3.199s CPU time, 0.243s GC time (major), 22 mutations, 223/26982 GCs (major/minor)

;; Second call on...
(time (memo-fact 10000000))
; => 0s CPU time, 10 mutations

</enscript>

=== Changelog

* 0.1 Initial version

=== License

  Copyright (c) 2013, Arthur Maciel
  All rights reserved.
  
  Redistribution and use in source and binary forms, with or without
  modification, are permitted provided that the following conditions are
  met:
  
  Redistributions of source code must retain the above copyright
  notice, this list of conditions and the following disclaimer.
  
  Redistributions in binary form must reproduce the above copyright
  notice, this list of conditions and the following disclaimer in the
  documentation and/or other materials provided with the distribution.
  
  Neither the name of the author nor the names of its contributors may
  be used to endorse or promote products derived from this software
  without specific prior written permission.
  
  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
  FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
  COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
  INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
  (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
  SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
  STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
  OF THE POSSIBILITY OF SUCH DAMAGE.