bard@THEORY.LCS.MIT.EDU (02/07/89)
> Then I was too obtuse. y-or-n-p reads a single character. yes-or-no-p > reads characters. I can switch buffers (C-x C-o) when the questioner uses > yes-or-no-p but not when it uses y-or-n-p. The y-or-n-p routine does not > allow one to go check things out because C-x is taken as a "no" answer. My > point is that they have two differences. One is the length of the answer > and the other is what you are allowed to do while answering. > > So, where I'm not worried about the question, y-or-n-p is fine, but I don't > mind having to type yes when I'm possibly in trouble. This has bothered me too. Here's my fairly baroque proposal for a fix, backed up by some code. y-or-n-p should accept answers other than y or n (which screws up the name, but who cares?). Here's a draft of the function; it has options like: r = recursive edit. This lets you go looking around the rest of the world and such, and still get back to the question. a = abort (almost like c-g, but can ask for confirmation -- is this complexity a good idea?) * = recursive edit in a less safe manner that lets you frob the position, window configuration, etc. (r restores all those things) I don't know how dangerous this may be. h = print a help message if y-or-n-p was called with one. ? = list these commands There is a confirm option. It can be the atom 'yes-or-no, which asks "Do you really mean it?" and wants a yes or no for an answer. I thought about a similar use of y-or-n, but I think people will get confused about whether it is "do you really mean it" (usual answer is y) or "type your answer again if you meant it". which are very different if you answered "n". Alternatively, the confirm option can be a function to call with some appropriate arguments; see the documentation. If you want to be *very* careful about confirmation, use the paranoid-confirm function I have listed. It generates a random number which the user has to type back at the computer to confirm the answer, forcing her to look at the prompt. Good for real paranoids, and calls of the form: (y-or-n-p "Destroy all your files, club you over the head with a frozen leg of lamb, shoot your spouse with a poisoned crossbow bolt, spray huge amounts of meta-hyper-fluorochlorocarbons into the atmosphere, send the Earth spiralling into the sun, and delete this buffer?" (function paranoid-confirm)) There's a variable controlling some assorted behavior which I thought might be obnoxious when I was playing with it. E.g., the command telling where the exit-recursive-edit command is is too slow, so I have some ways around it. Comments and improvements are welcome. Of course, if you run this y-or-n-p, it won't work on calls from C code. -- Bard the emacs gargoyle ;; Copyright (C) 1989 by Bard Bloom and the Free Software Foundation. ;; This code is distributed under the guarantee that it is an early ;; draft and needs to be thought out better before it is correct. ;; People are encouraged to adapt this code and distribute the revised ;; version to the network. (defvar y-or-n-p-nice '(recursive-edit slow abort) "Make y-or-n-p behave nicely. It's a list of atoms. recursive-edit ==> y-or-n-p tells you how to get out of a recursive edit slow ==========> if your computer is slow about substitute-command-keys, this prints a nice little message rather than doing nothing for a while. abort ===========> prompt you when you ask to abort a command. ") (defun y-or-n-p (question &optional confirm help) "Ask user a \"y or n\" question. Return t if answer is \"y\". No confirmation of the answer is requested unless CONFIRM is true; a single character is enough. Also accepts Space or Return to mean yes, or Delete to mean no. Other options: ? for help about y-or-n-p h prints the HELP argument if any. (Or calls it if it is a function) r invokes a recursive edit a aborts * invokes a recursive edit without some safety features. CONFIRM may be: 'yes-or-no -- confirmation is via yes-or-no-p. a function -- called (CONFIRM QUESTION HELP ANSWER) (where ANSWER is t or nil depending on what the user typed.) Should return a two-element list (answered answer): (nil anything) = ask the y-or-n-p question again (t t) = y-or-n-p returns t (t nil) = y-or-n-p returns nil " (let ((answered nil) (message (concat question " [ynhra?]")) answer c (recursive-edit-prelude (function (lambda () (if (memq 'recursive-edit y-or-n-p-nice) (progn (if (memq 'slow y-or-n-p-nice) (message "One moment please...")) (message (substitute-command-keys "Entering recursive edit -- \\[exit-recursive-edit] to return."))))))) ) (while (not answered) (message message) (setq c (downcase (read-char))) (cond ((memq c '(?y ?\ ?\n)) (setq answered t answer t)) ((memq c '(?n ?\C-?)) (setq answered t answer nil)) ((memq c '(?r)) (funcall recursive-edit-prelude) (save-window-excursion (save-excursion (save-restriction (widen) (recursive-edit)))) ;; no answer from the recursive edit, of course ) ((memq c '(?*)) (funcall recursive-edit-prelude) (recursive-edit)) ((memq c '(?a)) (if (if (memq 'abort y-or-n-p-nice) (let ((the-question question)) ;; damned dynamic binding! (new-y-or-n-p "Abort this command?" (function (lambda () (message "Abort `%s'" the-question))))) t) (error "`%s' aborted." question))) ((memq c '(?h)) (cond ((null help) (message "Sorry -- no help for this question.")) ((stringp help) (message help)) (t (funcall help))) (sit-for 2)) ((memq c '(??)) (message "Y[es], N[o], H[elp about question], R[ecursive edit], A[bort]") (sit-for 2)) (t (beep))) ;; now confirm it (maybe) (cond ((or (not answered) (not confirm)) ;; go on to next query ) ((eq confirm 'yes-or-no) (setq answered (yes-or-no-p (format "Just checking: do you really mean %s? " (if answer '\"Yes\" '\"No\"))))) (t (let ((conf (funcall confirm question help answer))) (setq answered (nth 0 conf) answer (nth 1 conf))))) ) answer)) (defun paranoid-confirm (q h a) (let* ((r (random)) (user-r (string-to-int (read-from-minibuffer (format "Type %d to confirm your %s answer to `%s':" r (if a "\"yes\"" "\"no\"") q) )))) (cond ((= r user-r) (list t a)) (t (message "...not confirmed...") (sit-for 2) '(nil nil)))))