macroexp.el 7.19 KB
Newer Older
1 2
;;; macroexp.el --- Additional macro-expansion support
;;
Glenn Morris's avatar
Glenn Morris committed
3
;; Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010 Free Software Foundation, Inc.
4 5 6 7 8 9
;;
;; Author: Miles Bader <miles@gnu.org>
;; Keywords: lisp, compiler, macros

;; This file is part of GNU Emacs.

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 13
;; the Free Software Foundation, either version 3 of the License, or
;; (at your option) any later version.
14 15 16 17 18 19 20

;; GNU Emacs 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 General Public License for more details.

;; You should have received a copy of the GNU General Public License
21
;; along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.
22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45

;;; Commentary:
;;
;; This file contains macro-expansions functions that are not defined in
;; the Lisp core, namely `macroexpand-all', which expands all macros in
;; a form, not just a top-level one.
;;

;;; Code:

;; Bound by the top-level `macroexpand-all', and modified to include any
;; macros defined by `defmacro'.
(defvar macroexpand-all-environment nil)

(defun maybe-cons (car cdr original-cons)
  "Return (CAR . CDR), using ORIGINAL-CONS if possible."
  (if (and (eq car (car original-cons)) (eq cdr (cdr original-cons)))
      original-cons
    (cons car cdr)))

;; We use this special macro to iteratively process forms and share list
;; structure of the result with the input.  Doing so recursively using
;; `maybe-cons' results in excessively deep recursion for very long
;; input forms.
46
(defmacro macroexp-accumulate (var+list &rest body)
47 48 49 50 51
  "Return a list of the results of evaluating BODY for each element of LIST.
Evaluate BODY with VAR bound to each `car' from LIST, in turn.
Return a list of the values of the final form in BODY.
The list structure of the result will share as much with LIST as
possible (for instance, when BODY just returns VAR unchanged, the
52 53 54 55 56
result will be eq to LIST).

\(fn (VAR LIST) BODY...)"
  (let ((var (car var+list))
	(list (cadr var+list))
57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91
	(shared (make-symbol "shared"))
	(unshared (make-symbol "unshared"))
	(tail (make-symbol "tail"))
	(new-el (make-symbol "new-el")))
    `(let* ((,shared ,list)
	    (,unshared nil)
	    (,tail ,shared)
	    ,var ,new-el)
       (while ,tail
	 (setq ,var (car ,tail)
	       ,new-el (progn ,@body))
	 (unless (eq ,var ,new-el)
	   (while (not (eq ,shared ,tail))
	     (push (pop ,shared) ,unshared))
	   (setq ,shared (cdr ,shared))
	   (push ,new-el ,unshared))
	 (setq ,tail (cdr ,tail)))
       (nconc (nreverse ,unshared) ,shared))))
(put 'macroexp-accumulate 'lisp-indent-function 1)

(defun macroexpand-all-forms (forms &optional skip)
  "Return FORMS with macros expanded.  FORMS is a list of forms.
If SKIP is non-nil, then don't expand that many elements at the start of
FORMS."
  (macroexp-accumulate (form forms)
    (if (or (null skip) (zerop skip))
	(macroexpand-all-1 form)
      (setq skip (1- skip))
      form)))

(defun macroexpand-all-clauses (clauses &optional skip)
  "Return CLAUSES with macros expanded.
CLAUSES is a list of lists of forms; any clause that's not a list is ignored.
If SKIP is non-nil, then don't expand that many elements at the start of
each clause."
92
  (macroexp-accumulate (clause clauses)
93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136
    (if (listp clause)
	(macroexpand-all-forms clause skip)
      clause)))

(defun macroexpand-all-1 (form)
  "Expand all macros in FORM.
This is an internal version of `macroexpand-all'.
Assumes the caller has bound `macroexpand-all-environment'."
  (if (and (listp form) (eq (car form) 'backquote-list*))
      ;; Special-case `backquote-list*', as it is normally a macro that
      ;; generates exceedingly deep expansions from relatively shallow input
      ;; forms.  We just process it `in reverse' -- first we expand all the
      ;; arguments, _then_ we expand the top-level definition.
      (macroexpand (macroexpand-all-forms form 1)
		   macroexpand-all-environment)
    ;; Normal form; get its expansion, and then expand arguments.
    (setq form (macroexpand form macroexpand-all-environment))
    (if (consp form)
	(let ((fun (car form)))
	  (cond
	   ((eq fun 'cond)
	    (maybe-cons fun (macroexpand-all-clauses (cdr form)) form))
	   ((eq fun 'condition-case)
	    (maybe-cons
	     fun
	     (maybe-cons (cadr form)
			 (maybe-cons (macroexpand-all-1 (nth 2 form))
				     (macroexpand-all-clauses (nthcdr 3 form) 1)
				     (cddr form))
			 (cdr form))
	     form))
	   ((eq fun 'defmacro)
	    (push (cons (cadr form) (cons 'lambda (cddr form)))
		  macroexpand-all-environment)
	    (macroexpand-all-forms form 3))
	   ((eq fun 'defun)
	    (macroexpand-all-forms form 3))
	   ((memq fun '(defvar defconst))
	    (macroexpand-all-forms form 2))
	   ((eq fun 'function)
	    (if (and (consp (cadr form)) (eq (car (cadr form)) 'lambda))
		(maybe-cons fun
			    (maybe-cons (macroexpand-all-forms (cadr form) 2)
					nil
137
					(cdr form))
138 139 140 141 142 143 144 145 146 147
			    form)
	      form))
	   ((memq fun '(let let*))
	    (maybe-cons fun
			(maybe-cons (macroexpand-all-clauses (cadr form) 1)
				    (macroexpand-all-forms (cddr form))
				    (cdr form))
			form))
	   ((eq fun 'quote)
	    form)
148 149 150 151 152
	   ((and (consp fun) (eq (car fun) 'lambda))
	    ;; Embedded lambda in function position.
	    (maybe-cons (macroexpand-all-forms fun 2)
			(macroexpand-all-forms (cdr form))
			form))
153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195
	   ;; The following few cases are for normal function calls that
	   ;; are known to funcall one of their arguments.  The byte
	   ;; compiler has traditionally handled these functions specially
	   ;; by treating a lambda expression quoted by `quote' as if it
	   ;; were quoted by `function'.  We make the same transformation
	   ;; here, so that any code that cares about the difference will
	   ;; see the same transformation.
	   ;; First arg is a function:
	   ((and (memq fun '(apply mapcar mapatoms mapconcat mapc))
		 (consp (cadr form))
		 (eq (car (cadr form)) 'quote))
	    ;; We don't use `maybe-cons' since there's clearly a change.
	    (cons fun
		  (cons (macroexpand-all-1 (cons 'function (cdr (cadr form))))
			(macroexpand-all-forms (cddr form)))))
	   ;; Second arg is a function:
	   ((and (eq fun 'sort)
		 (consp (nth 2 form))
		 (eq (car (nth 2 form)) 'quote))
	    ;; We don't use `maybe-cons' since there's clearly a change.
	    (cons fun
		  (cons (macroexpand-all-1 (cadr form))
			(cons (macroexpand-all-1
			       (cons 'function (cdr (nth 2 form))))
			      (macroexpand-all-forms (nthcdr 3 form))))))
	   (t
	    ;; For everything else, we just expand each argument (for
	    ;; setq/setq-default this works alright because the variable names
	    ;; are symbols).
	    (macroexpand-all-forms form 1))))
      form)))

;;;###autoload
(defun macroexpand-all (form &optional environment)
  "Return result of expanding macros at all levels in FORM.
If no macros are expanded, FORM is returned unchanged.
The second optional arg ENVIRONMENT specifies an environment of macro
definitions to shadow the loaded ones for use in file byte-compilation."
  (let ((macroexpand-all-environment environment))
    (macroexpand-all-1 form)))

(provide 'macroexp)

196
;; arch-tag: af9b8c24-c196-43bc-91e1-a3570790fa5a
197
;;; macroexp.el ends here