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+;;; srfi-39.scm --- Parameter objects
+
+;; Copyright (C) 2004, 2005, 2006, 2008, 2011 Free Software Foundation, Inc.
+;;
+;; This library is free software; you can redistribute it and/or
+;; modify it under the terms of the GNU Lesser General Public
+;; License as published by the Free Software Foundation; either
+;; version 3 of the License, or (at your option) any later version.
+;;
+;; This library 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
+;; Lesser General Public License for more details.
+;;
+;; You should have received a copy of the GNU Lesser General Public
+;; License along with this library; if not, write to the Free Software
+;; Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+
+;;; Author: Jose Antonio Ortega Ruiz <jao@gnu.org>
+;;; Date: 2004-05-05
+
+;;; Commentary:
+
+;; This is an implementation of SRFI-39 (Parameter objects).
+;;
+;; The implementation is based on Guile's fluid objects, and is, therefore,
+;; thread-safe (parameters are thread-local).
+;;
+;; In addition to the forms defined in SRFI-39 (`make-parameter',
+;; `parameterize'), a new procedure `with-parameters*' is provided.
+;; This procedures is analogous to `with-fluids*' but taking as first
+;; argument a list of parameter objects instead of a list of fluids.
+;;
+
+;;; Code:
+
+(define-module (srfi srfi-39)
+ ;; helper procedure not in srfi-39.
+ #:export (with-parameters*)
+ #:re-export (make-parameter
+ parameterize
+ current-input-port current-output-port current-error-port))
+
+(cond-expand-provide (current-module) '(srfi-39))
+
+(define (with-parameters* params values thunk)
+ (let more ((params params)
+ (values values)
+ (fluids '()) ;; fluids from each of PARAMS
+ (convs '())) ;; VALUES with conversion proc applied
+ (if (null? params)
+ (with-fluids* fluids convs thunk)
+ (more (cdr params) (cdr values)
+ (cons (parameter-fluid (car params)) fluids)
+ (cons ((parameter-converter (car params)) (car values)) convs)))))