Re: overlay (combine) lines

[Kevin Rodgers]

ry2ngh@gmail.com wrote:
> I am trying to figure out how to overlay lines of code.
>
> For example, if I have the following two lines, how can i combine the
> non blanks into one line.
>
> -----before overlay--------------
>   one           three
>           two             four
>
> -------after overlay--------------
>   one   two  three   four
>
> In the past on a mainframe I was able to do this using a primative
> line editor by typing an M and O on the line numbers as follows:
>
> 00M001  one           three
> 00O002          two             four
>
> resulting in only one line:
> 0000001 one   two   three  four

Here is some pure hackery:

(defun combine-next-line ()
  "Combine the next line with the current line.
The printable characters in the next line are used to replace the
whitespace characters in the same column of the current line."
  (let* ((this-line-beg (line-beginning-position))
         (next-line-end (line-end-position 2))
         (this-line (buffer-substring this-line-beg
                                      (line-end-position)))
         (next-line (buffer-substring (line-beginning-position 2)
                                      next-line-end))
         (column 0)
         (line-length (min (length this-line) (length next-line))))
    (while (< column line-length)
      (when (and (equal (char-syntax (aref this-line column)) ?\s)
                 (not (equal (char-syntax (aref next-line column)) ?\s)))
        (aset this-line column (aref next-line column)))
      (setq column (1+ column)))
    (delete-region this-line-beg next-line-end)
    (goto-char this-line-beg)
    (insert this-line)
    (when (< column (length next-line))
      (insert (substring next-line column)))))


--
Kevin Rodgers
Denver, Colorado, USA