1;;; macroexp.el --- Additional macro-expansion support
2;;
3;; Copyright (C) 2004, 2005, 2006, 2007 Free Software Foundation, Inc.
4;;
5;; Author: Miles Bader <miles@gnu.org>
6;; Keywords: lisp, compiler, macros
7
8;; This file is part of GNU Emacs.
9
10;; GNU Emacs is free software; you can redistribute it and/or modify
11;; it under the terms of the GNU General Public License as published by
12;; the Free Software Foundation; either version 2, or (at your option)
13;; any later version.
14
15;; GNU Emacs is distributed in the hope that it will be useful,
16;; but WITHOUT ANY WARRANTY; without even the implied warranty of
17;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
18;; GNU General Public License for more details.
19
20;; You should have received a copy of the GNU General Public License
21;; along with GNU Emacs; see the file COPYING.  If not, write to the
22;; Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
23;; Boston, MA 02110-1301, USA.
24
25;;; Commentary:
26;;
27;; This file contains macro-expansions functions that are not defined in
28;; the Lisp core, namely `macroexpand-all', which expands all macros in
29;; a form, not just a top-level one.
30;;
31
32;;; Code:
33
34;; Bound by the top-level `macroexpand-all', and modified to include any
35;; macros defined by `defmacro'.
36(defvar macroexpand-all-environment nil)
37
38(defun maybe-cons (car cdr original-cons)
39  "Return (CAR . CDR), using ORIGINAL-CONS if possible."
40  (if (and (eq car (car original-cons)) (eq cdr (cdr original-cons)))
41      original-cons
42    (cons car cdr)))
43
44;; We use this special macro to iteratively process forms and share list
45;; structure of the result with the input.  Doing so recursively using
46;; `maybe-cons' results in excessively deep recursion for very long
47;; input forms.
48(defmacro macroexp-accumulate (var+list &rest body)
49  "Return a list of the results of evaluating BODY for each element of LIST.
50Evaluate BODY with VAR bound to each `car' from LIST, in turn.
51Return a list of the values of the final form in BODY.
52The list structure of the result will share as much with LIST as
53possible (for instance, when BODY just returns VAR unchanged, the
54result will be eq to LIST).
55
56\(fn (VAR LIST) BODY...)"
57  (let ((var (car var+list))
58	(list (cadr var+list))
59	(shared (make-symbol "shared"))
60	(unshared (make-symbol "unshared"))
61	(tail (make-symbol "tail"))
62	(new-el (make-symbol "new-el")))
63    `(let* ((,shared ,list)
64	    (,unshared nil)
65	    (,tail ,shared)
66	    ,var ,new-el)
67       (while ,tail
68	 (setq ,var (car ,tail)
69	       ,new-el (progn ,@body))
70	 (unless (eq ,var ,new-el)
71	   (while (not (eq ,shared ,tail))
72	     (push (pop ,shared) ,unshared))
73	   (setq ,shared (cdr ,shared))
74	   (push ,new-el ,unshared))
75	 (setq ,tail (cdr ,tail)))
76       (nconc (nreverse ,unshared) ,shared))))
77(put 'macroexp-accumulate 'lisp-indent-function 1)
78
79(defun macroexpand-all-forms (forms &optional skip)
80  "Return FORMS with macros expanded.  FORMS is a list of forms.
81If SKIP is non-nil, then don't expand that many elements at the start of
82FORMS."
83  (macroexp-accumulate (form forms)
84    (if (or (null skip) (zerop skip))
85	(macroexpand-all-1 form)
86      (setq skip (1- skip))
87      form)))
88
89(defun macroexpand-all-clauses (clauses &optional skip)
90  "Return CLAUSES with macros expanded.
91CLAUSES is a list of lists of forms; any clause that's not a list is ignored.
92If SKIP is non-nil, then don't expand that many elements at the start of
93each clause."
94  (macroexp-accumulate (clause clauses)
95    (if (listp clause)
96	(macroexpand-all-forms clause skip)
97      clause)))
98
99(defun macroexpand-all-1 (form)
100  "Expand all macros in FORM.
101This is an internal version of `macroexpand-all'.
102Assumes the caller has bound `macroexpand-all-environment'."
103  (if (and (listp form) (eq (car form) 'backquote-list*))
104      ;; Special-case `backquote-list*', as it is normally a macro that
105      ;; generates exceedingly deep expansions from relatively shallow input
106      ;; forms.  We just process it `in reverse' -- first we expand all the
107      ;; arguments, _then_ we expand the top-level definition.
108      (macroexpand (macroexpand-all-forms form 1)
109		   macroexpand-all-environment)
110    ;; Normal form; get its expansion, and then expand arguments.
111    (setq form (macroexpand form macroexpand-all-environment))
112    (if (consp form)
113	(let ((fun (car form)))
114	  (cond
115	   ((eq fun 'cond)
116	    (maybe-cons fun (macroexpand-all-clauses (cdr form)) form))
117	   ((eq fun 'condition-case)
118	    (maybe-cons
119	     fun
120	     (maybe-cons (cadr form)
121			 (maybe-cons (macroexpand-all-1 (nth 2 form))
122				     (macroexpand-all-clauses (nthcdr 3 form) 1)
123				     (cddr form))
124			 (cdr form))
125	     form))
126	   ((eq fun 'defmacro)
127	    (push (cons (cadr form) (cons 'lambda (cddr form)))
128		  macroexpand-all-environment)
129	    (macroexpand-all-forms form 3))
130	   ((eq fun 'defun)
131	    (macroexpand-all-forms form 3))
132	   ((memq fun '(defvar defconst))
133	    (macroexpand-all-forms form 2))
134	   ((eq fun 'function)
135	    (if (and (consp (cadr form)) (eq (car (cadr form)) 'lambda))
136		(maybe-cons fun
137			    (maybe-cons (macroexpand-all-forms (cadr form) 2)
138					nil
139					(cadr form))
140			    form)
141	      form))
142	   ((memq fun '(let let*))
143	    (maybe-cons fun
144			(maybe-cons (macroexpand-all-clauses (cadr form) 1)
145				    (macroexpand-all-forms (cddr form))
146				    (cdr form))
147			form))
148	   ((eq fun 'quote)
149	    form)
150	   ((and (consp fun) (eq (car fun) 'lambda))
151	    ;; embedded lambda
152	    (maybe-cons (macroexpand-all-forms fun 2)
153			(macroexpand-all-forms (cdr form))
154			form))
155	   ;; The following few cases are for normal function calls that
156	   ;; are known to funcall one of their arguments.  The byte
157	   ;; compiler has traditionally handled these functions specially
158	   ;; by treating a lambda expression quoted by `quote' as if it
159	   ;; were quoted by `function'.  We make the same transformation
160	   ;; here, so that any code that cares about the difference will
161	   ;; see the same transformation.
162	   ;; First arg is a function:
163	   ((and (memq fun '(apply mapcar mapatoms mapconcat mapc))
164		 (consp (cadr form))
165		 (eq (car (cadr form)) 'quote))
166	    ;; We don't use `maybe-cons' since there's clearly a change.
167	    (cons fun
168		  (cons (macroexpand-all-1 (cons 'function (cdr (cadr form))))
169			(macroexpand-all-forms (cddr form)))))
170	   ;; Second arg is a function:
171	   ((and (eq fun 'sort)
172		 (consp (nth 2 form))
173		 (eq (car (nth 2 form)) 'quote))
174	    ;; We don't use `maybe-cons' since there's clearly a change.
175	    (cons fun
176		  (cons (macroexpand-all-1 (cadr form))
177			(cons (macroexpand-all-1
178			       (cons 'function (cdr (nth 2 form))))
179			      (macroexpand-all-forms (nthcdr 3 form))))))
180	   (t
181	    ;; For everything else, we just expand each argument (for
182	    ;; setq/setq-default this works alright because the variable names
183	    ;; are symbols).
184	    (macroexpand-all-forms form 1))))
185      form)))
186
187;;;###autoload
188(defun macroexpand-all (form &optional environment)
189  "Return result of expanding macros at all levels in FORM.
190If no macros are expanded, FORM is returned unchanged.
191The second optional arg ENVIRONMENT specifies an environment of macro
192definitions to shadow the loaded ones for use in file byte-compilation."
193  (let ((macroexpand-all-environment environment))
194    (macroexpand-all-1 form)))
195
196(provide 'macroexp)
197
198;;; arch-tag: af9b8c24-c196-43bc-91e1-a3570790fa5a
199;;; macroexp.el ends here
200