;;; -*- mode: Lisp; Syntax: Common-Lisp; -*-
;;;
;;; Copyright (c) 2009 by the authors.
;;;
;;; See LICENCE for details.

(in-package :hu.dwim.projectional-editor)

;;;;;;
;;; Reference API

(def (generic e) reference? (object)
  (:documentation "Returns TRUE if OBJECT is a reference, otherwise returns FALSE. Purely functional."))

(def (generic e) reference/find-value (document reference)
  (:documentation "Returns the value of REFERENCE within DOCUMENT. Purely functional."))

(def (generic e) (setf reference/find-value) (new-value document reference)
  (:documentation "Sets the value of REFERENCE within DOCUMENT to NEW-VALUE. Has side effects on DOCUMENT."))

(def type reference ()
  '(or number symbol string cons))

;;;;;;
;;; Reference API implementation

(def method reference? (object)
  (typep object 'reference))

(def method reference/find-value (document reference)
  (bind ((sb-ext::*evaluator-mode* :interpret))
    (eval `(bind ((document ',document))
             (declare (ignorable document))
             ,reference))))

(def method (setf reference/find-value) (new-value document reference)
  (bind ((sb-ext::*evaluator-mode* :interpret))
    (eval `(bind ((document ,document))
             (declare (ignorable document))
             (setf ,reference ,new-value)))))