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;;; shift-number.el --- Increase/decrease the number at point
;; Copyright © 2016 Alex Kost
;; Author: Alex Kost <alezost@gmail.com>
;; Created: 12 Apr 2016
;; Version: 0.1
;; Package-Version: 0.1
;; Package-Commit: ba3c1f2e6b01bf14aa1433c2a49098af1c025f7c
;; URL: https://github.com/alezost/shift-number.el
;; Keywords: convenience
;; 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 3 of the License, 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.
;; You should have received a copy of the GNU General Public License
;; along with this program. If not, see <http://www.gnu.org/licenses/>.
;;; Commentary:
;; Increase or decrease the number at point with `shift-number-up' and
;; `shift-number-down' commands.
;; To install the package manually, add the following to your init file:
;;
;; (add-to-list 'load-path "/path/to/shift-number-dir")
;; (autoload 'shift-number-up "shift-number" nil t)
;; (autoload 'shift-number-down "shift-number" nil t)
;; For more verbose description and a gif demonstration, see
;; <https://github.com/alezost/shift-number.el>.
;;; Code:
(defgroup shift-number nil
"Increase or decrease the number at point."
:group 'convenience)
(defcustom shift-number-regexp
(rx (group (one-or-more num)))
"Regexp for `shift-number' function.
The first parenthesized expression must match the number."
:type 'regexp
:group 'shift-number)
(defcustom shift-number-display-message nil
"If non-nil, display a message after shifting the current number."
:type 'boolean
:group 'shift-number)
(defun shift-number-in-regexp-p (regexp)
"Return non-nil, if point is inside REGEXP on the current line."
;; The code originates from `org-at-regexp-p'.
(save-excursion
(let ((pos (point))
(end (line-end-position))
found exit)
(beginning-of-line)
(while (and (not (or exit found))
(re-search-forward regexp end t))
(cond
((> (match-beginning 0) pos)
(setq exit t))
((>= (match-end 0) pos)
(setq found t))))
found)))
(defun shift-number (n)
"Change the number at point by N.
If there is no number at point, search forward till the end of
the current line and change it."
;; The whole number is removed and a new number is inserted in its
;; place, so `save-excursion' is not used, as it will put the point at
;; the beginning of the number. Instead, the point is saved and
;; restored later.
(let ((old-pos (point)))
(or (shift-number-in-regexp-p shift-number-regexp)
(re-search-forward shift-number-regexp (line-end-position) t)
(error "No number on the current line"))
(let* ((beg (match-beginning 1))
(end (match-end 1))
(old-num (string-to-number
(buffer-substring-no-properties beg end)))
(new-num (+ old-num n)))
(delete-region beg end)
(insert (number-to-string new-num))
(goto-char old-pos)
(when shift-number-display-message
(message "Number %d has been changed to number %d."
old-num new-num)))))
;;;###autoload
(defun shift-number-up (&optional arg)
"Increase the number at point (or on the current line) by ARG."
(interactive "p")
(shift-number arg))
;;;###autoload
(defun shift-number-down (&optional arg)
"Decrease the number at point (or on the current line) by ARG."
(interactive "p")
(shift-number (- arg)))
(provide 'shift-number)
;;; shift-number.el ends here