Re: Making code more Emacs Lisp-like

[Joseph Brenner <doom@kzsu.stanford.edu>]

Sarir Khamsi <sarir.khamsi@raytheon.com> writes:

> I wrote this function
>
> (defun sk-convert-to-ctor-init-list ()
>   "Convert a C++ member variable declaration to a ctor init list line.
> To use this, copy all member variable declarations into the constructor's member initialization list area and execute this command on each line. At the end of this command, it moves you to the next line setting it up for a key binding."
>   (interactive)
>   (save-excursion
>     (end-of-line)
>     (delete-horizontal-space)           ; delete whitespace at end of line
>     (backward-delete-char-untabify 1)   ; delete the ";"
>     (insert "(),")
>     (search-backward-regexp "[\t *]")     ; look for whitespace or "*"
>     (set-mark (+ (point) 1))              ; save the current position
>     (beginning-of-line)
>     (kill-region (point) (mark))
>     (c-indent-command))
>   (next-line 1))
>
> to take a region that containers C++ code for member variable
> declarations and convert it to a constructor's member init list. Is
> there a better (or a more ELisp) way than this approach? Thanks.

If you look up the Help screen for each function (using the default
bindings: cursor to the function, and do a "f1 f"), you'll often see
hints on better ways of doing things from inside of elisp.

For example, if you look up "set-mark", there's an example that's
easily adapted to what you're doing here:

>     (set-mark (+ (point) 1))              ; save the current position
>     (beginning-of-line)
>     (kill-region (point) (mark))

Would become:

   (let ((beg (point)))
      (beginning-of-line)
      (delete-region beg (point)))

The goal there is to avoid messing with the kill-ring or the mark
history if that's not necessary.  Otherwise you may surprise the
user with the unwanted side-effects.