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+;;; find-func.el --- find the definition of the elisp function near point
+
+;; Copyright (C) 1997 Free Software Foundation, Inc.
+
+;; Author: Jens Petersen <petersen@kurims.kyoto-u.ac.jp>
+;; Maintainer: petersen@kurims.kyoto-u.ac.jp
+;; Keywords: emacs-lisp, help, functions
+;; Created: 97/07/25
+
+;; 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.
+
+;; You should have received a copy of the GNU General Public License
+;; along with GNU Emacs; see the file COPYING.  If not, write to the
+;; Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+;; Boston, MA 02111-1307, USA.
+
+;;; Commentary:
+;;
+;; The funniest thing about this is that I can't imagine why a package
+;; so obviously useful as this hasn't been written before!!
+;; This probably belongs in "help.el" or somewhere like that.
+;;
+;; Put this file in your `load-path', byte-compile it and add the
+;; following code in your init file:
+;;
+;; ;;; find-func
+;; (load "find-function")
+;; (global-set-key [(control ?c) ?f] 'find-function)
+;; (global-set-key [(control ?c) ?4 ?f] 'find-function-other-window)
+;; (global-set-key [(control ?c) ?5 ?f] 'find-function-other-frame)
+;; (global-set-key [(control ?c) ?k] 'find-function-on-key)
+;;
+;; and away you go!  It does pretty much what you would expect,
+;; putting the cursor at the definition of the function at point.
+;;
+;; The code is adapted from `describe-function', `describe-key'
+;; ("help.el") and `fff-find-loaded-emacs-lisp-function' (Noah Friedman's
+;; "fff.el").
+
+;;; To do:
+;;
+;; o custom?
+;;
+;; o improve handling of advice'd functions? (at the moment it goes to
+;; the advice, not the actual definition)
+
+;;;; Code:
+
+;;; User variables:
+
+(defvar find-function-function 'function-at-point
+  "*The function used by `find-function' to select the function near
+point.
+
+For example `function-at-point' or `function-called-at-point'.")
+
+(defvar find-function-source-path nil
+  "The default list of directories where find-function searches.
+
+If this variable is `nil' then find-function searches `load-path' by
+default.")
+
+
+;;; Functions:
+
+(defun find-function-noselect (function &optional path)
+  "Returns list `(buffer point)' pointing to the definition of FUNCTION.
+
+Finds the Emacs Lisp library containing the definition of FUNCTION
+in a buffer and places point before the definition.  The buffer is
+not selected.
+
+If the optional argument PATH is given, the library where FUNCTION is
+defined is searched in PATH instead of `load-path' (see
+`find-function-source-path')."
+  (and (subrp (symbol-function function))
+       (error "%s is a primitive function" function))
+  (if (not function)
+      (error "You didn't specify a function"))
+  (let ((def (symbol-function function))
+        library aliases)
+    (while (symbolp def)
+      (or (eq def function)
+          (if aliases
+              (setq aliases (concat aliases
+                                    (format ", which is an alias for %s"
+                                            (symbol-name def))))
+            (setq aliases (format "an alias for %s" (symbol-name
+                                                       def)))))
+      (setq function (symbol-function function)
+            def (symbol-function function)))
+    (if aliases
+        (message aliases))
+    (setq library
+          (cond ((eq (car-safe def) 'autoload)
+                 (nth 1 def))
+                ((describe-function-find-file function))))
+    (if (null library)
+        (error (format "`%s' is not in `load-history'" function)))
+    (if (string-match "\\(\\.elc?\\'\\)" library)
+        (setq library (substring library 0 (match-beginning 1))))
+    (let* ((path (or path find-function-source-path))
+           (compression (or (rassq 'jka-compr-handler file-name-handler-alist)
+                            (member 'crypt-find-file-hook find-file-hooks)))
+           (filename (or (locate-library (concat library ".el")
+                                         t path)
+                         (locate-library library t path)
+                         (if compression
+                             (or (locate-library (concat library ".el.gz")
+                                                 t path)
+                                 (locate-library (concat library ".gz")
+                                                 t path))))))
+      (if (not filename)
+          (error "The library \"%s\" is not in the path." library))
+      (save-excursion
+        (set-buffer (find-file-noselect filename))
+        (save-match-data
+          (let (;; avoid defconst, defgroup, defvar (any others?)
+                (regexp (format "^\\s-*(def[^cgv\W]\\w+\\s-+%s\\s-" function))
+                (syntable (syntax-table)))
+            (set-syntax-table emacs-lisp-mode-syntax-table)
+            (goto-char (point-min))
+            (if (prog1
+                    (re-search-forward regexp nil t)
+                  (set-syntax-table syntable))
+                (progn
+                  (beginning-of-line)
+                  (list (current-buffer) (point)))
+              (error "Cannot find definition of %s" function))))))))
+
+(defun function-at-point ()
+  (or (condition-case ()
+          (let ((stab (syntax-table)))
+            (unwind-protect
+                (save-excursion
+                  (set-syntax-table emacs-lisp-mode-syntax-table)
+                  (or (not (zerop (skip-syntax-backward "_w")))
+                      (eq (char-syntax (char-after (point))) ?w)
+                      (eq (char-syntax (char-after (point))) ?_)
+                      (forward-sexp -1))
+                  (skip-chars-forward "`'")
+                  (let ((obj (read (current-buffer))))
+                    (and (symbolp obj) (fboundp obj) obj)))
+              (set-syntax-table stab)))
+        (error nil))
+      (condition-case ()
+          (save-excursion
+            (save-restriction
+              (narrow-to-region (max (point-min) (- (point) 1000)) (point-max))
+              (backward-up-list 1)
+              (forward-char 1)
+              (let (obj)
+                (setq obj (read (current-buffer)))
+                (and (symbolp obj) (fboundp obj) obj))))
+        (error nil))))
+
+(defun find-function-read-function ()
+  "Read and return a function, defaulting to the one near point.
+
+The function named by `find-function-function' is used to select the
+default function."
+  (let ((fn (funcall find-function-function))
+        (enable-recursive-minibuffers t)
+        val)
+    (setq val (completing-read
+               (if fn
+                   (format "Find function (default %s): " fn)
+                 "Find function: ")
+               obarray 'fboundp t))
+    (list (if (equal val "")
+              fn (intern val)))))
+
+(defun find-function-do-it (function path switch-fn)
+  "find elisp FUNCTION in PATH and display it with SWITCH-FN.
+Point is saved if FUNCTION is in the current buffer."
+  (let ((orig-point (point))
+        (buffer-point (find-function-noselect function path)))
+    (if buffer-point
+        (progn
+          (if (eq (current-buffer) (car buffer-point))
+              (push-mark orig-point))
+          (funcall switch-fn (car buffer-point))
+          (goto-char (elt buffer-point 1))
+          (recenter 0)))))
+
+(defun find-function (function &optional path)
+  "Find the definition of the function near point in the current window.
+
+Finds the Emacs Lisp library containing the definition of the function
+near point (selected by `find-function-function') and places point
+before the definition.  Point is saved if FUNCTION is in the current
+buffer.
+
+If the optional argument PATH is given, the library where FUNCTION is
+defined is searched in PATH instead of `load-path'"
+  (interactive (find-function-read-function))
+  (find-function-do-it function path 'switch-to-buffer))
+
+(defun find-function-other-window (function &optional path)
+  "Find the definition of the function near point in the other window.
+
+Finds the Emacs Lisp package containing the definition of the function
+near point (selected by `find-function-function') and places point
+before the definition.  Point is saved if FUNCTION is in the current
+buffer.
+
+If the optional argument PATH is given, the package where FUNCTION is
+defined is searched in PATH instead of `load-path'"
+  (interactive (find-function-read-function))
+  (find-function-do-it function path 'switch-to-buffer-other-window))
+
+(defun find-function-other-frame (function &optional path)
+  "Find the definition of the function near point in the another frame.
+
+Finds the Emacs Lisp package containing the definition of the function
+near point (selected by `find-function-function') and places point
+before the definition.  Point is saved if FUNCTION is in the current
+buffer.
+
+If the optional argument PATH is given, the package where FUNCTION is
+defined is searched in PATH instead of `load-path'"
+  (interactive (find-function-read-function))
+  (find-function-do-it function path 'switch-to-buffer-other-frame))
+
+(defun find-function-on-key (key)
+  "Find the function that KEY invokes.  KEY is a string.
+Point is saved if FUNCTION is in the current buffer."
+  (interactive "kFind function on key: ")
+  (let ((defn (key-binding key)))
+    (if (or (null defn) (integerp defn))
+        (message "%s is undefined" (key-description key))
+      (if (and (consp defn) (not (eq 'lambda (car-safe defn))))
+          (message "runs %s" (prin1-to-string defn))
+        (find-function-other-window defn)))))
+
+(provide 'find-func)
+
+;;; find-func.el ends here
+