Apropos commands and regexps

[Kim F. Storm]

I was thinking about the use of regexps in connection with the various
apropos commands.

We often advise new users to use e.g. C-h a or M-x apropos (also
accessible through the Help menu).

However, these commands prompts like this:

        Apropos command (regexp):

which may be nonsense to some novice users.


Wouldn't it be simpler (for a novice user -- and for advanced users
too) to simply write one or more words (substrings) and then search
for all combinations of those words (substrings) in the relevant list.

E.g. C-h a open file RET  would find any matching

        open.*file and file.*open

BTW, this obvious example doesn't find `find-file' :-(
Maybe we should have a defalias open-file -> find-file ?

Of course, if the input is already a regexp (e.g. if it does not
contain any spaces), it should be used directly.  Below is a patch
to show the concept:

Index: apropos.el
===================================================================
RCS file: /cvs/emacs/lisp/apropos.el,v
retrieving revision 1.84
diff -c -r1.84 apropos.el
*** apropos.el  4 May 2002 14:51:16 -0000       1.84
--- apropos.el  11 May 2002 23:55:10 -0000
***************
*** 122,127 ****
--- 122,130 ----
  (defvar apropos-regexp nil
    "Regexp used in current apropos run.")
  
+ (defvar apropos-orig-regexp nil
+   "Regexp as entered by user.")
+ 
  (defvar apropos-files-scanned ()
    "List of elc files already scanned in current run of 
`apropos-documentation'.")
  
***************
*** 219,224 ****
--- 222,245 ----
      (and label button)))
  
  
+ (defun apropos-rewrite-regexp (regexp)
+   "Rewrite a list of words to a regexp matching all permutations.
+ If REGEXP is already a regexp, don't modify it."
+   (setq apropos-orig-regexp regexp)
+   (if (and (string-match " " regexp)
+          (string-equal (regexp-quote regexp) regexp))
+       ;; We don't actually make a regexp matching all permutations.
+       ;; Instead, for e.g. "a b c", we make a regexp matching
+       ;; any combination of two or more words like this:
+       ;; (a|b|c).*(a|b|c) which may give some false matches,
+       ;; but as long as it also gives the right ones, that's ok.
+       (let ((words (split-string regexp "[ \t]+"))
+           res)
+       (dolist (w words)
+         (setq res (concat (or res "\\(") (if res "\\|" "") w)))
+       (concat res "\\).*" res "\\)"))
+     regexp))
+     
  ;;;###autoload
  (define-derived-mode apropos-mode fundamental-mode "Apropos"
    "Major mode for following hyperlinks in output of apropos commands.
***************
*** 262,267 ****
--- 283,289 ----
                                       "or function ")
                                   "(regexp): "))
                     current-prefix-arg))
+   (setq apropos-regexp (apropos-rewrite-regexp apropos-regexp))
    (let ((message
         (let ((standard-output (get-buffer-create "*Apropos*")))
           (print-help-return-message 'identity))))
***************
*** 304,309 ****
--- 326,332 ----
  show unbound symbols and key bindings, which is a little more
  time-consuming.  Returns list of symbols and documentation found."
    (interactive "sApropos symbol (regexp): \nP")
+   (setq apropos-regexp (apropos-rewrite-regexp apropos-regexp))
    (setq apropos-accumulator
        (apropos-internal apropos-regexp
                          (and (not do-all)
***************
*** 371,376 ****
--- 394,400 ----
  at the function and at the names and values of properties.
  Returns list of symbols and values found."
    (interactive "sApropos value (regexp): \nP")
+   (setq apropos-regexp (apropos-rewrite-regexp apropos-regexp))
    (or do-all (setq do-all apropos-do-all))
    (setq apropos-accumulator ())
     (let (f v p)
***************
*** 397,402 ****
--- 421,427 ----
  bindings.
  Returns list of symbols and documentation found."
    (interactive "sApropos documentation (regexp): \nP")
+   (setq apropos-regexp (apropos-rewrite-regexp apropos-regexp))
    (or do-all (setq do-all apropos-do-all))
    (setq apropos-accumulator () apropos-files-scanned ())
    (let ((standard-input (get-buffer-create " apropos-temp"))
***************
*** 590,596 ****
  If SPACING is non-nil, it should be a string;
  separate items with that string."
    (if (null apropos-accumulator)
!       (message "No apropos matches for `%s'" apropos-regexp)
      (setq apropos-accumulator
          (sort apropos-accumulator (lambda (a b)
                                      (string-lessp (car a) (car b)))))
--- 615,621 ----
  If SPACING is non-nil, it should be a string;
  separate items with that string."
    (if (null apropos-accumulator)
!       (message "No apropos matches for `%s'" apropos-orig-regexp)
      (setq apropos-accumulator
          (sort apropos-accumulator (lambda (a b)
                                      (string-lessp (car a) (car b)))))


-- 
Kim F. Storm <address@hidden> http://www.cua.dk