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[emacs.git] / lisp / regi.el
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1 ;;; regi.el --- REGular expression Interpreting engine
3 ;; Copyright (C) 1993 Free Software Foundation, Inc.
5 ;; Author: 1993 Barry A. Warsaw, Century Computing, Inc. <bwarsaw@cen.com>
6 ;; Maintainer: bwarsaw@cen.com
7 ;; Created: 24-Feb-1993
8 ;; Version: 1.8
9 ;; Last Modified: 1993/06/01 21:33:00
10 ;; Keywords: extensions, matching
12 ;; This file is part of GNU Emacs.
14 ;; GNU Emacs is free software; you can redistribute it and/or modify
15 ;; it under the terms of the GNU General Public License as published by
16 ;; the Free Software Foundation; either version 2, or (at your option)
17 ;; any later version.
19 ;; GNU Emacs is distributed in the hope that it will be useful,
20 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
21 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
22 ;; GNU General Public License for more details.
24 ;; You should have received a copy of the GNU General Public License
25 ;; along with GNU Emacs; see the file COPYING. If not, write to the
26 ;; Free Software Foundation, Inc., 59 Temple Place - Suite 330,
27 ;; Boston, MA 02111-1307, USA.
29 ;;; Code:
32 (defun regi-pos (&optional position col-p)
33 "Return the character position at various buffer positions.
34 Optional POSITION can be one of the following symbols:
36 `bol' == beginning of line
37 `boi' == beginning of indentation
38 `eol' == end of line [default]
39 `bonl' == beginning of next line
40 `bopl' == beginning of previous line
42 Optional COL-P non-nil returns `current-column' instead of character position."
43 (save-excursion
44 (cond
45 ((eq position 'bol) (beginning-of-line))
46 ((eq position 'boi) (back-to-indentation))
47 ((eq position 'bonl) (forward-line 1))
48 ((eq position 'bopl) (forward-line -1))
49 (t (end-of-line)))
50 (if col-p (current-column) (point))))
52 (defun regi-mapcar (predlist func &optional negate-p case-fold-search-p)
53 "Build a regi frame where each element of PREDLIST appears exactly once.
54 The frame contains elements where each member of PREDLIST is
55 associated with FUNC, and optionally NEGATE-P and CASE-FOLD-SEARCH-P."
56 (let (frame tail)
57 (if (or negate-p case-fold-search-p)
58 (setq tail (list negate-p)))
59 (if case-fold-search-p
60 (setq tail (append tail (list case-fold-search-p))))
61 (while predlist
62 (let ((element (list (car predlist) func)))
63 (if tail
64 (setq element (append element tail)))
65 (setq frame (append frame (list element))
66 predlist (cdr predlist))
68 frame))
71 (defun regi-interpret (frame &optional start end)
72 "Interpret the regi frame FRAME.
73 If optional START and END are supplied, they indicate the region of
74 interest, and the buffer is narrowed to the beginning of the line
75 containing START, and beginning of the line after the line containing
76 END. Otherwise, point and mark are not set and processing continues
77 until your FUNC returns the `abort' symbol (see below). Beware! Not
78 supplying a START or END could put you in an infinite loop.
80 A regi frame is a list of entries of the form:
82 (PRED FUNC [NEGATE-P [CASE-FOLD-SEARCH]])
84 PRED is a predicate against which each line in the region is tested,
85 and if a match occurs, FUNC is `eval'd. Point is then moved to the
86 beginning of the next line, the frame is reset and checking continues.
87 If a match doesn't occur, the next entry is checked against the
88 current line until all entries in the frame are checked. At this
89 point, if no match occurred, the frame is reset and point is moved to
90 the next line. Checking continues until every line in the region is
91 checked. Optional NEGATE-P inverts the result of PRED before FUNC is
92 called and `case-fold-search' is bound to the optional value of
93 CASE-FOLD-SEARCH for the PRED check.
95 PRED can be a string, variable, function or one of the following
96 symbols: t, nil, `begin', `end', and `every'. If PRED is a string, or
97 a variable or list that evaluates to a string, it is interpreted as a
98 regular expression and is matched against the current line (from the
99 beginning) using `looking-at'. If PRED does not evaluate to a string,
100 it is interpreted as a binary value (nil or non-nil).
102 PRED can also be one of the following symbols:
104 t -- always produces a true outcome
105 `begin' -- always executes before anything else
106 `end' -- always executes after everything else
107 `every' -- execute after frame is matched on a line
109 Note that NEGATE-P and CASE-FOLD-SEARCH are meaningless if PRED is one
110 of these special symbols. Only the first occurrence of each symbol in
111 a frame entry is used, the rest are ignored.
113 Your FUNC can return values which control regi processing. If a list
114 is returned from your function, it can contain any combination of the
115 following elements:
117 the symbol `continue'
118 Tells regi to continue processing frame-entries after a match,
119 instead of resetting to the first entry and advancing to the next
120 line, as is the default behavior. When returning this symbol,
121 you must take care not to enter an infinite loop.
123 the symbol `abort'
124 Tells regi to terminate processing this frame. any end
125 frame-entry is still processed.
127 the list `(frame . NEWFRAME)'
128 Tells regi to use NEWFRAME as its current frame. In other words,
129 your FUNC can modify the executing regi frame on the fly.
131 the list `(step . STEP)'
132 Tells regi to move STEP number of lines forward during normal
133 processing. By default, regi moves forward 1 line. STEP can be
134 negative, but be careful of infinite loops.
136 You should usually take care to explicitly return nil from your
137 function if no action is to take place. Your FUNC will always be
138 `eval'ed. The following variables will be temporarily bound to some
139 useful information:
141 `curline'
142 the current line in the buffer, as a string
144 `curframe'
145 the full, current frame being executed
147 `curentry'
148 the current frame entry being executed."
150 (save-excursion
151 (save-restriction
152 (let (begin-tag end-tag every-tag current-frame working-frame donep)
154 ;; set up the narrowed region
155 (and start
157 (let* ((tstart start)
158 (start (min start end))
159 (end (max start end)))
160 (narrow-to-region
161 (progn (goto-char end) (regi-pos 'bonl))
162 (progn (goto-char start) (regi-pos 'bol)))))
164 ;; lets find the special tags and remove them from the working
165 ;; frame. note that only the last special tag is used.
166 (mapcar
167 (function
168 (lambda (entry)
169 (let ((pred (car entry))
170 (func (car (cdr entry))))
171 (cond
172 ((eq pred 'begin) (setq begin-tag func))
173 ((eq pred 'end) (setq end-tag func))
174 ((eq pred 'every) (setq every-tag func))
176 (setq working-frame (append working-frame (list entry))))
177 ) ; end-cond
179 frame) ; end-mapcar
181 ;; execute the begin entry
182 (eval begin-tag)
184 ;; now process the frame
185 (setq current-frame working-frame)
186 (while (not (or donep (eobp)))
187 (let* ((entry (car current-frame))
188 (pred (nth 0 entry))
189 (func (nth 1 entry))
190 (negate-p (nth 2 entry))
191 (case-fold-search (nth 3 entry))
192 match-p)
193 (catch 'regi-throw-top
194 (cond
195 ;; we are finished processing the frame for this line
196 ((not current-frame)
197 (setq current-frame working-frame) ;reset frame
198 (forward-line 1)
199 (throw 'regi-throw-top t))
200 ;; see if predicate evaluates to a string
201 ((stringp (setq match-p (eval pred)))
202 (setq match-p (looking-at match-p)))
203 ) ; end-cond
205 ;; now that we've done the initial matching, check for
206 ;; negation of match
207 (and negate-p
208 (setq match-p (not match-p)))
210 ;; if the line matched, package up the argument list and
211 ;; funcall the FUNC
212 (if match-p
213 (let* ((curline (buffer-substring
214 (regi-pos 'bol)
215 (regi-pos 'eol)))
216 (curframe current-frame)
217 (curentry entry)
218 (result (eval func))
219 (step (or (cdr (assq 'step result)) 1))
221 ;; changing frame on the fly?
222 (if (assq 'frame result)
223 (setq working-frame (cdr (assq 'frame result))))
225 ;; continue processing current frame?
226 (if (memq 'continue result)
227 (setq current-frame (cdr current-frame))
228 (forward-line step)
229 (setq current-frame working-frame))
231 ;; abort current frame?
232 (if (memq 'abort result)
233 (progn
234 (setq donep t)
235 (throw 'regi-throw-top t)))
236 ) ; end-let
238 ;; else if no match occurred, then process the next
239 ;; frame-entry on the current line
240 (setq current-frame (cdr current-frame))
242 ) ; end-if match-p
243 ) ; end catch
244 ) ; end let
246 ;; after every cycle, evaluate every-tag
247 (eval every-tag)
248 ) ; end-while
250 ;; now process the end entry
251 (eval end-tag)))))
254 (provide 'regi)
255 ;;; regi.el ends here