general-purpose.el - a general-forms-resource-utility

[Andreas Roehler <andreas.roehler@easy-emacs.de>]

There are general usable functions scattered in the
source files, which are useful in a lot of
circumstances and could be callable in a given context.

Roman-to-latin- and Latin-to-roman-numbers for example.

Just today I saw

(defun region-around-match (&optional n)
  (set-mark (match-beginning n))
  (goto-char (match-end n)))

(defun region-to-string ()
  (buffer-substring (min (point) (mark)) (max (point) (mark))))

in mlsupport.el.

To have an (indexed) collection of all these goodies,
not only developers would gain an additional - sorted -
resource: This would also be useful for beginners to
learn Elisp - as function given there will be rather
basic ones, avoiding complexity. Also the Elisp-Manual
could refer to in order to give more examples, to
deepen understanding.

To show up such basic utilities one by one and in
relation might help finding errors and/or to optimize
usage.

Already started to collect some forms (example below)
but realize, this should not be done by hand.

Post this here, as there are probably more ideas to
consider before a major writing effort starts.

At the moment I see the following requirements at such
a general-resource-utility:

- take a given function or form where the point is in
  and prompt the user where to sort it (as groups in
  customize deliver a hierarchy and system)

- display a list of clickable functions or forms the
  way `apropos' does; i.e. M-x `general-resource-utility'
  RET `string-strip' should display several
  string-strip-utilities to examine, insert at point etc.

- allow users to edit the collection via
  copy-and-paste; provide some automated indexing
  afterward

- display related topics as customize does with
  parent groups

- collect resources from inside Emacs and third party
  stuff separately. (As a lot of users and me too use
  such stuff, it should not be impossible to collect
  and use it, provided it doesn't not disturb
  distribution. There might be - and should be probably
  - a warning at least once in that case.)

---

Thought to use/adapt cus-edit.el as a starting
point.

Please send your suggestions and/or objections.

__
Andreas Roehler

;;;

;; Please look with patience at this decent
   beginning :)

;;;_. * move related functions

(defun skip-blank-lines-backward ()
  " "
  (interactive)
  (while (looking-at "[ \t]*$")
      (forward-line -1))
  (forward-line 1))

(defun skip-blank-lines-forward ()
  " "
  (interactive)
  (while (looking-at "[ \t\n]")
    (forward-line 1))
  (forward-line -1))


;;;_. * string related functions
;;;_. ** strip-whitespace
;;;_. *** string-strip

(defun string-strip (str beforep afterp)
  "Strip STR of any leading (if BEFOREP) and/or trailing (if AFTERP) space.
"
  (string-match (concat "\\`" (if beforep "\\s-*")
            "\\(.*?\\)" (if afterp "\\s-*\n?")
            "\\'") str)
  (match-string 1 str))

;; Source: comment-string-strip, newcomment.el, GNU Emacs 22.0.50.1  ;;

;;;_. *** truncate-string-left

(defun concat-and-truncate-string-left (str prefix newlen)
  ;; leave space for ... on the left
  (let ((len (length str))
    (lenprefix (length prefix))
    substr)
    (if (<= len newlen)
    str
      (setq newlen (max 0 (- newlen lenprefix)))
      (setq substr (substring str (max 0 (- len 1 newlen))))
      (concat prefix substr))))

;; Example:
;; (concat-and-truncate-string-left "dasddddd" "+++" 4)
;; -> "+++dd"

;; following ediff-truncate-string-left from ediff-init.el

;;;_. *** nonempty-string-p

(defsubst nonempty-string-p (string)
  (and (stringp string) (not (string= string ""))))

;; Source: ediff-nonempty-string-p; ediff-init.el ---
;; Macros, variables, and defsubsts used by Ediff
;; Author: Michael Kifer <kifer@cs.sunysb.edu> ;;

;;;_. *** kill-trailing-spaces

;;;_. *** clean-out-spaces

(defun string-reverse (s)
  "Return the mirror image of string S, without any trailing space."
  (comment-string-strip (concat (nreverse (string-to-list s))) nil t))

;; Source: comment-string-reverse, newcomment.el, GNU Emacs 22.0.50.1 ;;

;;;_. ** numeral-string-conversions
;;;_. *** decimal-to-roman

(defvar w3-roman-characters "ivxLCDMVX" "Roman numerals.")

(defun w3-decimal-to-roman (n)
  "Convert from decimal to roman numerals"

  (let ((curmod 1000)
    (str "")
    (j 7)
    i2 k curcnt)
    (while (>= curmod 1)
      (if (>= n curmod)
      (progn
        (setq curcnt (/ n curmod)
          n (- n (* curcnt curmod)))
        (if (= 4 (% curcnt 5))
        (setq i2 (+ j (if (> curcnt 5) 1 0))
              str (format "%s%c%c" str
                  (aref w3-roman-characters (1- j))
                  (aref w3-roman-characters i2)))
          (progn
        (if (>= curcnt 5)
            (setq str (format "%s%c" str (aref w3-roman-characters j))
              curcnt (- curcnt 5)))
        (setq k 0)
        (while (< k curcnt)
          (setq str (format "%s%c" str
                    (aref w3-roman-characters (1- j)))
            k (1+ k)))))))
      (setq curmod (/ curmod 10)
        j (- j 2)))
    str))

;; Source: w3-display.el --- W3 display engine.   Author: William M. 
Perry <wmperry@cs.indiana.edu" ;;

;;;_. *** decimal-to-alpha

(defun w3-decimal-to-alpha (n)
  "Convert from decimal to alphabetical (a, b, c, ..., aa, ab,...)"
  (cond
   ((< n 1) (char-to-string ?Z))
   ((<= n 26) (char-to-string (+ ?A (1- n))))
   (t (concat (w3-decimal-to-alpha (/ n 26))
          (w3-decimal-to-alpha (% n 26))))))

;;   Source: w3-display.el --- W3 display engine.   Author: William M. 
Perry <wmperry@cs.indiana.edu" ;;

;;;_. * clipboard related functions
;;;_. ** clipboard and x-select-enable-clipboard

(defun clipboard-yank ()
  "Insert the clipboard contents, or the last stretch of killed text."
  (interactive)
  (let ((x-select-enable-clipboard t))
    (yank)))

(defun clipboard-kill-ring-save (beg end)
  "Copy region to kill ring, and save in the X clipboard."
  (interactive "r")
  (let ((x-select-enable-clipboard t))
    (kill-ring-save beg end)))

(defun clipboard-kill-region (beg end)
  "Kill the region, and save it in the X clipboard."
  (interactive "r")
  (let ((x-select-enable-clipboard t))
    (kill-region beg end)))

;; Source: menu-bar.el ;;

;;;;; End