Mark region and insert prefix

Question

I recently switched from vi to emacs, and now I'm porting my most important macros to emacs. What I need most is the ability to prefix a marked region of text with a string, including header and footer:

Original:

line 1
line 2
line 3
line 4

After marking the 2nd and 3rd line, I want emacs to ask me for a number, say 002, and do the following, ideally remembering my choice:

line 1
*#002# Start:
*$line 2
*$line 3
*#002# End.
line 4

So far, I have managed to insert start and end tags with the following code:

(defun comment-region (start end)
  "Insert COBOL comments."
  (interactive "r")
  (save-excursion 
    (goto-char end) (insert "*#xxx# End.\n")
    (goto-char start) (insert "*#xxx# Start:\n")
    ))

However, I can't seem to find out how to prefix all lines in the region with *$ and how to make emacs ask me for a string.

Any ideas?

Answer 1

I've taken to solving this type of problems by dynamically generating a snippet with yasnippet lately.

Here is the code:

(require 'yasnippet)
(defun cobol-comment-region (beg end)
  "comment a region as cobol (lines 2,3 commented)

line 1
*#002# Start:
*$line 2
*$line 3
*#002# End.
line 4
"
  (interactive "*r")
  (setq beg (progn
             (goto-char beg)
             (point-at-bol 1))
       end (progn
             (goto-char end)
             (if (bolp)
                 (point)
               (forward-line 1)
               (if (bolp)
                   (point)
                 (insert "\n")
                 (point)))))
  (let* ((str (replace-regexp-in-string
               "^" "*$" (buffer-substring-no-properties beg (1- end))))
         (template (concat "*#${1:002}# Start:\n"
                           str
                           "\n*#$1# End.\n"))
         (yas-indent-line 'fixed))
    (delete-region beg end)
    (yas-expand-snippet template)))

video included, what???

Here is a video of it in action:

Answer 2

This is a better approach, but its a little awkward at the end...

(defun comment-region (start end prefix)
  "Insert COBOL comments."
  (interactive "r\nsPrefix: ")
  (save-excursion
    (narrow-to-region start end)
    (goto-char (point-min))
    (insert "*#" prefix " #Start.\n")
    (while (not (eobp))
      (insert "*$")
      (forward-line))
    (insert "*#" prefix " #End.\n")
    (widen)))

Answer 3

Your best bet is to use cobol-mode instead of writing ad hoc functions yourself.

The file header contains detailed instructions on how to use it.

Then just use Cx C which runs the command comment-region , which comments the region according to the major mode (in your case, cobol).