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;;; map-ynp.el -- General-purpose boolean question-asker.
;;; Copyright (C) 1991 Free Software Foundation, Inc.
;;; Written by Roland McGrath.
;;;
;;; This program 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 1, or (at your option)
;;; any later version.
;;;
;;; This program 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.
;;;
;;; A copy of the GNU General Public License can be obtained from this
;;; program's author (send electronic mail to roland@ai.mit.edu) or from
;;; the Free Software Foundation, Inc., 675 Mass Ave, Cambridge, MA
;;; 02139, USA.
;;;
;;; map-y-or-n-p is a general-purpose question-asking function.
;;; It asks a series of y/n questions (a la y-or-n-p), and decides to
;;; applies an action to each element of a list based on the answer.
;;; The nice thing is that you also get some other possible answers
;;; to use, reminiscent of query-replace: ! to answer y to all remaining
;;; questions; ESC or q to answer n to all remaining questions; . to answer
;;; y once and then n for the remainder; and you can get help with C-h.
(defun map-y-or-n-p-help (object objects action)
(format "Type SPC or `y' to %s the current %s;
DEL or `n' to skip the current %s;
! to %s all remaining %s;
ESC or `q' to exit;
or . (period) to %s the current %s and exit."
action object object action objects action object))
;;;###autoload
(defun map-y-or-n-p (prompter actor list &optional help)
"Ask a series of boolean questions.
Takes args PROMPTER ACTOR LIST, and optional arg HELP.
LIST is a list of objects, or a function of no arguments to return the next
object or nil.
PROMPTER is a function of one arg (an object from LIST),
which returns a string to be used as the prompt for that object.
If the return value is not a string, it is eval'd to get the answer.
So, it may be nil to ignore the object, t to act on the object without
asking the user, or a form to do a more complex prompt.
PROMPTER may instead be a string, in which case the prompt is
\(format PROMPTER OBJECT\).
ACTOR is a function of one arg (an object from LIST),
which gets called with each object that the user answers `yes' for.
If HELP is given, it is a list (OBJECT OBJECTS ACTION),
where OBJECT is a string giving the singular noun for an elt of LIST;
OBJECTS is the plural noun for elts of LIST, and ACTION is a transitive
verb describing ACTOR. The default is \(\"object\" \"objects\" \"act on\"\).
At the prompts, the user may enter y, Y, or SPC to act on that object;
n, N, or DEL to skip that object; ! to act on all following objects;
ESC or q to exit (skip all following objects); . (period) to act on the
current object and then exit; or \\[help-command] to get help.
Returns the number of actions taken."
(let ((old-help-form help-form)
(help-form (cons 'map-y-or-n-p-help
(or help '("object" "objects" "act on"))))
(actions 0)
prompt
char
(next (if (or (symbolp list)
(subrp list)
(compiled-function-p list)
(and (consp list)
(eq (car list) 'lambda)))
list
(function (lambda ()
(if list
(prog1
(car list)
(setq list (cdr list)))
nil)))))
elt)
(if (stringp prompter)
(setq prompter (` (lambda (object)
(format (, prompter) object)))))
(while (setq elt (funcall next))
(setq prompt (funcall prompter elt))
(if (stringp prompt)
(progn
;; Prompt the user about this object.
(let ((cursor-in-echo-area t))
(message "%s(y, n, ! ., q, or %s)"
prompt (key-description (char-to-string help-char)))
(setq char (read-char)))
(cond ((or (= ?q char)
(= ?\e char))
(setq next (function (lambda () nil))))
((or (= ?y char)
(= ?Y char)
(= ? char))
;; Act on the object.
(let ((help-form old-help-form))
(funcall actor elt))
(setq actions (1+ actions)))
((or (= ?n char)
(= ?N char)
(= ?\^? char))
;; Skip the object.
)
((= ?. char)
;; Act on the object and then exit.
(funcall actor elt)
(setq actions (1+ actions)
next (function (lambda () nil))))
((= ?! char)
;; Act on this and all following objects.
(if (eval (funcall prompter elt))
(progn
(funcall actor elt)
(setq actions (1+ actions))))
(while (setq elt (funcall next))
(if (eval (funcall prompter elt))
(progn
(funcall actor elt)
(setq actions (1+ actions))))))
((= ?? char)
(setq unread-command-char help-char)
(setq next (` (lambda ()
(setq next '(, next))
'(, elt)))))
(t
;; Random char.
(message "Type %s for help."
(key-description (char-to-string help-char)))
(beep)
(sit-for 1)
(setq next (` (lambda ()
(setq next '(, next))
'(, elt)))))))
(if (eval prompt)
(progn
(funcall actor elt)
(setq actions (1+ actions))))))
;; Clear the last prompt from the minibuffer.
(message "")
;; Return the number of actions that were taken.
actions))
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