lisp/regi.el

   1 ;;; regi.el --- REGular expression Interpreting engine
   2
   3 ;; Copyright (C) 1993 Free Software Foundation, Inc.
   4
   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
  11
  12 ;; This file is part of GNU Emacs.
  13
  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.
  18
  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.
  23
  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.
  28
  29 ;;; Commentary:
  30
  31 ;;; Code:
  32
  33 \f
  34 (defun regi-pos (&optional position col-p)
  35   "Return the character position at various buffer positions.
  36 Optional POSITION can be one of the following symbols:
  37
  38 `bol'  == beginning of line
  39 `boi'  == beginning of indentation
  40 `eol'  == end of line [default]
  41 `bonl' == beginning of next line
  42 `bopl' == beginning of previous line
  43
  44 Optional COL-P non-nil returns `current-column' instead of character position."
  45   (save-excursion
  46     (cond
  47      ((eq position 'bol)  (beginning-of-line))
  48      ((eq position 'boi)  (back-to-indentation))
  49      ((eq position 'bonl) (forward-line 1))
  50      ((eq position 'bopl) (forward-line -1))
  51      (t (end-of-line)))
  52     (if col-p (current-column) (point))))
  53
  54 (defun regi-mapcar (predlist func &optional negate-p case-fold-search-p)
  55   "Build a regi frame where each element of PREDLIST appears exactly once.
  56 The frame contains elements where each member of PREDLIST is
  57 associated with FUNC, and optionally NEGATE-P and CASE-FOLD-SEARCH-P."
  58   (let (frame tail)
  59     (if (or negate-p case-fold-search-p)
  60         (setq tail (list negate-p)))
  61     (if case-fold-search-p
  62         (setq tail (append tail (list case-fold-search-p))))
  63     (while predlist
  64       (let ((element (list (car predlist) func)))
  65         (if tail
  66             (setq element (append element tail)))
  67         (setq frame (append frame (list element))
  68               predlist (cdr predlist))
  69         ))
  70     frame))
  71
  72 \f
  73 (defun regi-interpret (frame &optional start end)
  74   "Interpret the regi frame FRAME.
  75 If optional START and END are supplied, they indicate the region of
  76 interest, and the buffer is narrowed to the beginning of the line
  77 containing START, and beginning of the line after the line containing
  78 END.  Otherwise, point and mark are not set and processing continues
  79 until your FUNC returns the `abort' symbol (see below).  Beware!  Not
  80 supplying a START or END could put you in an infinite loop.
  81
  82 A regi frame is a list of entries of the form:
  83
  84      (PRED FUNC [NEGATE-P [CASE-FOLD-SEARCH]])
  85
  86 PRED is a predicate against which each line in the region is tested,
  87 and if a match occurs, FUNC is `eval'd.  Point is then moved to the
  88 beginning of the next line, the frame is reset and checking continues.
  89 If a match doesn't occur, the next entry is checked against the
  90 current line until all entries in the frame are checked.  At this
  91 point, if no match occurred, the frame is reset and point is moved to
  92 the next line.  Checking continues until every line in the region is
  93 checked.  Optional NEGATE-P inverts the result of PRED before FUNC is
  94 called and `case-fold-search' is bound to the optional value of
  95 CASE-FOLD-SEARCH for the PRED check.
  96
  97 PRED can be a string, variable, function or one of the following
  98 symbols: t, nil, `begin', `end', and `every'.  If PRED is a string, or
  99 a variable or list that evaluates to a string, it is interpreted as a
 100 regular expression and is matched against the current line (from the
 101 beginning) using `looking-at'.  If PRED does not evaluate to a string,
 102 it is interpreted as a binary value (nil or non-nil).
 103
 104 PRED can also be one of the following symbols:
 105
 106 t       -- always produces a true outcome
 107 `begin' -- always executes before anything else
 108 `end'   -- always executes after everything else
 109 `every' -- execute after frame is matched on a line
 110
 111 Note that NEGATE-P and CASE-FOLD-SEARCH are meaningless if PRED is one
 112 of these special symbols.  Only the first occurrence of each symbol in
 113 a frame entry is used, the rest are ignored.
 114
 115 Your FUNC can return values which control regi processing.  If a list
 116 is returned from your function, it can contain any combination of the
 117 following elements:
 118
 119 the symbol `continue'
 120      Tells regi to continue processing frame-entries after a match,
 121      instead of resetting to the first entry and advancing to the next
 122      line, as is the default behavior.  When returning this symbol,
 123      you must take care not to enter an infinite loop.
 124
 125 the symbol `abort'
 126      Tells regi to terminate processing this frame.  any end
 127      frame-entry is still processed.
 128
 129 the list `(frame . NEWFRAME)'
 130      Tells regi to use NEWFRAME as its current frame.  In other words,
 131      your FUNC can modify the executing regi frame on the fly.
 132
 133 the list `(step . STEP)'
 134      Tells regi to move STEP number of lines forward during normal
 135      processing.  By default, regi moves forward 1 line.  STEP can be
 136      negative, but be careful of infinite loops.
 137
 138 You should usually take care to explicitly return nil from your
 139 function if no action is to take place.  Your FUNC will always be
 140 `eval'ed.  The following variables will be temporarily bound to some
 141 useful information:
 142
 143 `curline'
 144      the current line in the buffer, as a string
 145
 146 `curframe'
 147      the full, current frame being executed
 148
 149 `curentry'
 150      the current frame entry being executed."
 151
 152   (save-excursion
 153     (save-restriction
 154       (let (begin-tag end-tag every-tag current-frame working-frame donep)
 155
 156         ;; set up the narrowed region
 157         (and start
 158              end
 159              (let* ((tstart start)
 160                     (start (min start end))
 161                     (end   (max start end)))
 162                (narrow-to-region
 163                 (progn (goto-char end) (regi-pos 'bonl))
 164                 (progn (goto-char start) (regi-pos 'bol)))))
 165
 166         ;; lets find the special tags and remove them from the working
 167         ;; frame. note that only the last special tag is used.
 168         (mapcar
 169          (function
 170           (lambda (entry)
 171             (let ((pred (car entry))
 172                   (func (car (cdr entry))))
 173               (cond
 174                ((eq pred 'begin) (setq begin-tag func))
 175                ((eq pred 'end)   (setq end-tag func))
 176                ((eq pred 'every) (setq every-tag func))
 177                (t
 178                 (setq working-frame (append working-frame (list entry))))
 179                ) ; end-cond
 180               )))
 181          frame) ; end-mapcar
 182
 183         ;; execute the begin entry
 184         (eval begin-tag)
 185
 186         ;; now process the frame
 187         (setq current-frame working-frame)
 188         (while (not (or donep (eobp)))
 189           (let* ((entry            (car current-frame))
 190                  (pred             (nth 0 entry))
 191                  (func             (nth 1 entry))
 192                  (negate-p         (nth 2 entry))
 193                  (case-fold-search (nth 3 entry))
 194                  match-p)
 195             (catch 'regi-throw-top
 196               (cond
 197                ;; we are finished processing the frame for this line
 198                ((not current-frame)
 199                 (setq current-frame working-frame) ;reset frame
 200                 (forward-line 1)
 201                 (throw 'regi-throw-top t))
 202                ;; see if predicate evaluates to a string
 203                ((stringp (setq match-p (eval pred)))
 204                 (setq match-p (looking-at match-p)))
 205                ) ; end-cond
 206
 207               ;; now that we've done the initial matching, check for
 208               ;; negation of match
 209               (and negate-p
 210                    (setq match-p (not match-p)))
 211
 212               ;; if the line matched, package up the argument list and
 213               ;; funcall the FUNC
 214               (if match-p
 215                    (let* ((curline (buffer-substring
 216                                     (regi-pos 'bol)
 217                                     (regi-pos 'eol)))
 218                           (curframe current-frame)
 219                           (curentry entry)
 220                           (result (eval func))
 221                           (step (or (cdr (assq 'step result)) 1))
 222                           )
 223                      ;; changing frame on the fly?
 224                      (if (assq 'frame result)
 225                          (setq working-frame (cdr (assq 'frame result))))
 226
 227                      ;; continue processing current frame?
 228                      (if (memq 'continue result)
 229                          (setq current-frame (cdr current-frame))
 230                        (forward-line step)
 231                        (setq current-frame working-frame))
 232
 233                      ;; abort current frame?
 234                      (if (memq 'abort result)
 235                          (progn
 236                            (setq donep t)
 237                            (throw 'regi-throw-top t)))
 238                      ) ; end-let
 239
 240                 ;; else if no match occurred, then process the next
 241                 ;; frame-entry on the current line
 242                 (setq current-frame (cdr current-frame))
 243
 244                 ) ; end-if match-p
 245               ) ; end catch
 246             ) ; end let
 247
 248           ;; after every cycle, evaluate every-tag
 249           (eval every-tag)
 250           ) ; end-while
 251
 252         ;; now process the end entry
 253         (eval end-tag)))))
 254
 255 \f
 256 (provide 'regi)
 257
 258 ;;; regi.el ends here