module/srfi/srfi-111.scm

   1 ;;; srfi-111.scm -- SRFI 111 Boxes
   2
   3 ;;      Copyright (C) 2014 Free Software Foundation, Inc.
   4 ;;
   5 ;; This library is free software; you can redistribute it and/or
   6 ;; modify it under the terms of the GNU Lesser General Public
   7 ;; License as published by the Free Software Foundation; either
   8 ;; version 3 of the License, or (at your option) any later version.
   9 ;;
  10 ;; This library is distributed in the hope that it will be useful,
  11 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
  12 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13 ;; Lesser General Public License for more details.
  14 ;;
  15 ;; You should have received a copy of the GNU Lesser General Public
  16 ;; License along with this library; if not, write to the Free Software
  17 ;; Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  18
  19 (define-module (srfi srfi-111)
  20   #:use-module (srfi srfi-9)
  21   #:use-module (srfi srfi-9 gnu)
  22   #:export (box box? unbox set-box!))
  23
  24 (cond-expand-provide (current-module) '(srfi-111))
  25
  26 (define-record-type <box>
  27   (box value)
  28   box?
  29   (value unbox set-box!))
  30
  31 (set-record-type-printer! <box>
  32   (lambda (box port)
  33     (display "#<box " port)
  34     (display (number->string (object-address box) 16) port)
  35     (display " value: ")
  36     (write (unbox box) port)
  37     (display ">" port)))