;;; Copyright (C) 2025 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 program.  If not, see
;;; <http://www.gnu.org/licenses/>.

;;; Commentary:
;;;
;;; Properties are a lispy way to associate random info with random
;;; objects.  Traditionally properties are implemented as an alist or a
;;; plist actually pertaining to the object in question.
;;;
;;; These "object properties" have the advantage that they can be
;;; associated with any object, even if the object has no plist. Object
;;; properties are good when you are extending pre-existing objects in
;;; unexpected ways. They also present a pleasing, uniform
;;; procedure-with-setter interface. But if you have a data type that
;;; always has properties, it's often still best to store those
;;; properties within the object itself.
;;;
;;; Code:


(define-module (ice-9 object-properties)
  ;; FIXME: Change to #:export when deprecated bindings removed.
  #:replace (make-object-property))

(define (make-object-property)
  ;; Weak tables are thread-safe.
  (let ((prop (make-weak-key-hash-table)))
    (make-procedure-with-setter
     (lambda (obj) (hashq-ref prop obj))
     (lambda (obj val) (hashq-set! prop obj val)))))