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+;;; thingatpt.el --- Get the `thing' at point
+
+;; Copyright (C) 1991,1992,1993 Free Software Foundation, Inc.
+
+;; Author: Mike Williams <mikew@gopher.dosli.govt.nz>
+;; Keywords: extensions
+;; Created: Thu Mar 28 13:48:23 1991
+;; Version: $Revision: 1.16 $
+
+;; This file is part of GNU Emacs.
+
+;; GNU Emacs is free software; you can redistribute it and/or modify
+;; it under the terms of the GNU General Public License as published by
+;; the Free Software Foundation; either version 2, or (at your option)
+;; any later version.
+
+;; 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.
+
+;;; Commentary:
+;;
+;; This file provides routines for getting the `thing' at the location of
+;; point, whatever that `thing' happens to be.  The `thing' is defined by
+;; it's beginning and end positions in the buffer.
+;;
+;; The function bounds-of-thing-at-point finds the beginning and end
+;; positions by moving first forward to the end of the `thing', and then
+;; backwards to the beginning.  By default, it uses the corresponding
+;; forward-`thing' operator (eg. forward-word, forward-line).
+;;
+;; Special cases are allowed for using properties associated with the named
+;; `thing': 
+;;
+;;   forward-op		Function to call to skip forward over a `thing' (or
+;;                      with a negative argument, backward).
+;;                      
+;;   beginning-op	Function to call to skip to the beginning of a `thing'.
+;;   end-op		Function to call to skip to the end of a `thing'.
+;;
+;; Reliance on existing operators means that many `things' can be accessed
+;; without further code:  eg.
+;;     (thing-at-point 'line)
+;;     (thing-at-point 'page)
+
+;;; Code:
+
+(provide 'thingatpt)
+
+;;=== Version =============================================================
+
+(defconst thing@pt-version (substring "$Revision: 1.16 $" 11 -2)
+  "The revision number of thing@pt (as string).  The complete RCS id is:
+
+  $Id: thing@pt.el,v 1.16 1993/09/30 23:54:56 mike Exp $")
+
+;;=== Basic movement ======================================================
+
+;;;###autoload
+(defun forward-thing (THING &optional N)
+  "Move forward to the end of the next THING."
+  (let ((forward-op (or (get THING 'forward-op)
+			(intern-soft (format "forward-%s" THING)))))
+    (if (fboundp forward-op)
+	(funcall forward-op (or N 1))
+      (error "Can't determine how to move over %ss" THING))))
+
+;;=== General routines ====================================================
+
+;;;###autoload
+(defun bounds-of-thing-at-point (THING)
+  "Determine the start and end buffer locations for the THING at point,
+where THING is an entity for which there is a either a corresponding
+forward-THING operation, or corresponding beginning-of-THING and
+end-of-THING operations, eg. 'word, 'sentence, 'defun.
+  Return a cons cell '(start . end) giving the start and end positions."
+  (let ((orig (point)))
+    (condition-case nil
+	(save-excursion
+	  (let ((end (progn 
+		       (funcall 
+			(or (get THING 'end-op) 
+			    (function (lambda () (forward-thing THING 1)))))
+		       (point)))
+		(beg (progn 
+		       (funcall 
+			(or (get THING 'beginning-op) 
+			    (function (lambda () (forward-thing THING -1)))))
+		       (point))))
+	    (if (and beg end (<= beg orig) (< orig end))
+		(cons beg end))))
+      (error nil))))
+
+;;;###autoload
+(defun thing-at-point (THING)
+  "Return the THING at point, where THING is an entity defined by
+bounds-of-thing-at-point."
+  (let ((bounds (bounds-of-thing-at-point THING)))
+    (if bounds 
+	(buffer-substring (car bounds) (cdr bounds)))))
+
+;;=== Go to beginning/end =================================================
+
+(defun beginning-of-thing (THING)
+  (let ((bounds (bounds-of-thing-at-point THING)))
+    (or bounds (error "No %s here" THING))
+    (goto-char (car bounds))))
+
+(defun end-of-thing (THING)
+  (let ((bounds (bounds-of-thing-at-point THING)))
+    (or bounds (error "No %s here" THING))
+    (goto-char (cdr bounds))))
+
+;;=== Special cases =======================================================
+
+;;--- Sexps ---
+
+(defun in-string-p ()
+  (let ((orig (point)))
+    (save-excursion
+      (beginning-of-defun)
+      (nth 3 (parse-partial-sexp (point) orig)))))
+
+(defun end-of-sexp ()
+  (let ((char-syntax (char-syntax (char-after (point)))))
+    (if (or (eq char-syntax ?\))
+	    (and (eq char-syntax ?\") (in-string-p)))
+	(forward-char 1)
+      (forward-sexp 1))))
+
+(put 'sexp 'end-op 'end-of-sexp)
+
+;;--- Lists ---
+
+(put 'list 'end-op (function (lambda () (up-list 1))))
+(put 'list 'beginning-op 'backward-sexp)
+
+;;--- Filenames ---
+
+(defvar file-name-chars "~/A-Za-z0-9---_.${}#%,"
+  "Characters allowable in filenames.")
+
+(put 'filename 'end-op    
+     (function (lambda () (skip-chars-forward file-name-chars))))
+(put 'filename 'beginning-op
+     (function (lambda () (skip-chars-backward file-name-chars (point-min)))))
+
+;;--- Whitespace ---
+
+(defun forward-whitespace (ARG)
+  (interactive "p")
+  (if (natnump ARG) 
+      (re-search-forward "[ \t]+\\|\n" nil nil ARG)
+    (while (< ARG 0)
+      (if (re-search-backward "[ \t]+\\|\n" nil nil)
+	  (or (eq (char-after (match-beginning 0)) 10)
+	      (skip-chars-backward " \t")))
+      (setq ARG (1+ ARG)))))
+
+;;--- Buffer ---
+
+(put 'buffer 'end-op 'end-of-buffer)
+(put 'buffer 'beginning-op 'beginning-of-buffer)
+
+;;--- Symbols ---
+
+(defun forward-symbol (ARG)
+  (interactive "p")
+  (if (natnump ARG) 
+      (re-search-forward "\\(\\sw\\|\\s_\\)+" nil nil ARG)
+    (while (< ARG 0)
+      (if (re-search-backward "\\(\\sw\\|\\s_\\)+" nil nil)
+	  (skip-syntax-backward "w_"))
+      (setq ARG (1+ ARG)))))
+
+;;=== Aliases =============================================================
+
+(defun word-at-point () (thing-at-point 'word))
+(defun sentence-at-point () (thing-at-point 'sentence))
+
+(defun read-from-whole-string (STR)
+  "Read a lisp expression from STR, signalling an error if the entire string
+was not used."
+  (let* ((read-data (read-from-string STR))
+	 (more-left 
+	  (condition-case nil
+	      (progn (read-from-string (substring STR (cdr read-data)))
+		     t)
+	    (end-of-file nil))))
+    (if more-left
+	(error "Can't read whole string")
+      (car read-data))))
+
+(defun form-at-point (&optional THING PRED) 
+  (let ((sexp (condition-case nil 
+		  (read-from-whole-string (thing-at-point (or THING 'sexp)))
+		(error nil))))
+    (if (or (not PRED) (funcall PRED sexp)) sexp)))
+
+(defun sexp-at-point ()   (form-at-point 'sexp))
+(defun symbol-at-point () (form-at-point 'sexp 'symbolp))
+(defun number-at-point () (form-at-point 'sexp 'numberp))
+(defun list-at-point ()   (form-at-point 'list 'listp))
+
+;; thingatpt.el ends here.