code.delx.au - gnu-emacs/blob - lisp/thingatpt.el

   1 ;;; thingatpt.el --- Get the `thing' at point
   2
   3 ;; Copyright (C) 1991,1992,1993 Free Software Foundation, Inc.
   4
   5 ;; Author: Mike Williams <mikew@gopher.dosli.govt.nz>
   6 ;; Keywords: extensions, matching, mouse
   7 ;; Created: Thu Mar 28 13:48:23 1991
   8
   9 ;; This file is part of GNU Emacs.
  10
  11 ;; GNU Emacs is free software; you can redistribute it and/or modify
  12 ;; it under the terms of the GNU General Public License as published by
  13 ;; the Free Software Foundation; either version 2, or (at your option)
  14 ;; any later version.
  15
  16 ;; GNU Emacs is distributed in the hope that it will be useful,
  17 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
  18 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  19 ;; GNU General Public License for more details.
  20
  21 ;;; Commentary: ===========================================================
  22 ;;
  23 ;; This file provides routines for getting the `thing' at the location of
  24 ;; point, whatever that `thing' happens to be.  The `thing' is defined by
  25 ;; it's beginning and end positions in the buffer.
  26 ;;
  27 ;; The function bounds-of-thing-at-point finds the beginning and end
  28 ;; positions by moving first forward to the end of the `thing', and then
  29 ;; backwards to the beginning.  By default, it uses the corresponding
  30 ;; forward-`thing' operator (eg. forward-word, forward-line).
  31 ;;
  32 ;; Special cases are allowed for using properties associated with the named
  33 ;; `thing':
  34 ;;
  35 ;;   forward-op         Function to call to skip forward over a `thing' (or
  36 ;;                      with a negative argument, backward).
  37 ;;
  38 ;;   beginning-op       Function to call to skip to the beginning of a `thing'.
  39 ;;   end-op             Function to call to skip to the end of a `thing'.
  40 ;;
  41 ;; Reliance on existing operators means that many `things' can be accessed
  42 ;; without further code:  eg.
  43 ;;     (thing-at-point 'line)
  44 ;;     (thing-at-point 'page)
  45
  46 ;;; Code: =================================================================
  47
  48 (provide 'thingatpt)
  49
  50 ;;=== Basic movement ======================================================
  51
  52 ;;;###autoload
  53 (defun forward-thing (THING &optional N)
  54   "Move forward to the end of the next THING."
  55   (let ((forward-op (or (get THING 'forward-op)
  56                         (intern-soft (format "forward-%s" THING)))))
  57     (if (fboundp forward-op)
  58         (funcall forward-op (or N 1))
  59       (error "Can't determine how to move over %ss" THING))))
  60
  61 ;;=== General routines ====================================================
  62
  63 ;;;###autoload
  64 (defun bounds-of-thing-at-point (THING)
  65   "Determine the start and end buffer locations for the THING at point,
  66 where THING is an entity for which there is a either a corresponding
  67 forward-THING operation, or corresponding beginning-of-THING and
  68 end-of-THING operations, eg. 'word, 'sentence, 'defun.
  69   Return a cons cell '(start . end) giving the start and end positions."
  70   (let ((orig (point)))
  71     (condition-case nil
  72         (save-excursion
  73           (let ((end (progn
  74                        (funcall
  75                         (or (get THING 'end-op)
  76                             (function (lambda () (forward-thing THING 1)))))
  77                        (point)))
  78                 (beg (progn
  79                        (funcall
  80                         (or (get THING 'beginning-op)
  81                             (function (lambda () (forward-thing THING -1)))))
  82                        (point))))
  83             (if (and beg end (<= beg orig) (< orig end))
  84                 (cons beg end))))
  85       (error nil))))
  86
  87 ;;;###autoload
  88 (defun thing-at-point (THING)
  89   "Return the THING at point, where THING is an entity defined by
  90 bounds-of-thing-at-point."
  91   (let ((bounds (bounds-of-thing-at-point THING)))
  92     (if bounds
  93         (buffer-substring (car bounds) (cdr bounds)))))
  94
  95 ;;=== Go to beginning/end =================================================
  96
  97 (defun beginning-of-thing (THING)
  98   (let ((bounds (bounds-of-thing-at-point THING)))
  99     (or bounds (error "No %s here" THING))
 100     (goto-char (car bounds))))
 101
 102 (defun end-of-thing (THING)
 103   (let ((bounds (bounds-of-thing-at-point THING)))
 104     (or bounds (error "No %s here" THING))
 105     (goto-char (cdr bounds))))
 106
 107 ;;=== Special cases =======================================================
 108
 109 ;;--- Sexps ---
 110
 111 (defun in-string-p ()
 112   (let ((orig (point)))
 113     (save-excursion
 114       (beginning-of-defun)
 115       (nth 3 (parse-partial-sexp (point) orig)))))
 116
 117 (defun end-of-sexp ()
 118   (let ((char-syntax (char-syntax (char-after (point)))))
 119     (if (or (eq char-syntax ?\))
 120             (and (eq char-syntax ?\") (in-string-p)))
 121         (forward-char 1)
 122       (forward-sexp 1))))
 123
 124 (put 'sexp 'end-op 'end-of-sexp)
 125
 126 ;;--- Lists ---
 127
 128 (put 'list 'end-op (function (lambda () (up-list 1))))
 129 (put 'list 'beginning-op 'backward-sexp)
 130
 131 ;;--- Filenames ---
 132
 133 (defvar file-name-chars "~/A-Za-z0-9---_.${}#%,"
 134   "Characters allowable in filenames.")
 135
 136 (put 'filename 'end-op
 137      (function (lambda () (skip-chars-forward file-name-chars))))
 138 (put 'filename 'beginning-op
 139      (function (lambda () (skip-chars-backward file-name-chars (point-min)))))
 140
 141 ;;--- Whitespace ---
 142
 143 (defun forward-whitespace (ARG)
 144   (interactive "p")
 145   (if (natnump ARG)
 146       (re-search-forward "[ \t]+\\|\n" nil nil ARG)
 147     (while (< ARG 0)
 148       (if (re-search-backward "[ \t]+\\|\n" nil nil)
 149           (or (eq (char-after (match-beginning 0)) 10)
 150               (skip-chars-backward " \t")))
 151       (setq ARG (1+ ARG)))))
 152
 153 ;;--- Buffer ---
 154
 155 (put 'buffer 'end-op 'end-of-buffer)
 156 (put 'buffer 'beginning-op 'beginning-of-buffer)
 157
 158 ;;--- Symbols ---
 159
 160 (defun forward-symbol (ARG)
 161   (interactive "p")
 162   (if (natnump ARG)
 163       (re-search-forward "\\(\\sw\\|\\s_\\)+" nil nil ARG)
 164     (while (< ARG 0)
 165       (if (re-search-backward "\\(\\sw\\|\\s_\\)+" nil nil)
 166           (skip-syntax-backward "w_"))
 167       (setq ARG (1+ ARG)))))
 168
 169 ;;=== Aliases =============================================================
 170
 171 (defun word-at-point () (thing-at-point 'word))
 172 (defun sentence-at-point () (thing-at-point 'sentence))
 173
 174 (defun read-from-whole-string (STR)
 175   "Read a lisp expression from STR, signalling an error if the entire string
 176 was not used."
 177   (let* ((read-data (read-from-string STR))
 178          (more-left
 179           (condition-case nil
 180               (progn (read-from-string (substring STR (cdr read-data)))
 181                      t)
 182             (end-of-file nil))))
 183     (if more-left
 184         (error "Can't read whole string")
 185       (car read-data))))
 186
 187 (defun form-at-point (&optional THING PRED)
 188   (let ((sexp (condition-case nil
 189                   (read-from-whole-string (thing-at-point (or THING 'sexp)))
 190                 (error nil))))
 191     (if (or (not PRED) (funcall PRED sexp)) sexp)))
 192
 193 (defun sexp-at-point ()   (form-at-point 'sexp))
 194 (defun symbol-at-point () (form-at-point 'sexp 'symbolp))
 195 (defun number-at-point () (form-at-point 'sexp 'numberp))
 196 (defun list-at-point ()   (form-at-point 'list 'listp))
 197
 198 ;; thingatpt.el ends here.