Elisp macros for cleaning LaTeX-code - emacs

Question

does anyone know of some good elisp macros for cleaning up LaTeX code?
I do a lot of LaTeX editing of other peoples sources and I'd like to extend my set of clean up tools since not everyone organize their code in the manner I like it ;-)
One in particular would be interesting, to run function X on a buffer and get all LaTeX environments (\begin{...} and \end{...} pairs) to sit on lines of their own, this helps readability of the code.
I could try this myself, but would like to hear suggestions as to a best practice for programming such a function, e.g. it should of course not introduce blank lines of its own.
suggestions?
Edit: For the archives, here are my current version based on the answer given (assumes the use of auctex). It more or less suits my needs at the moment. I added the y-or-n test just to be able to detect corner cases that I had not thought of.
(defun enviro-split ()
"Find begin and end macros, and put them on their own line."
(interactive)
(save-excursion
(beginning-of-buffer)
;; loop over document looking for begin and end macros
(while (re-search-forward "\\\\\\(begin\\|end\\)" nil t)
(catch 'continue
; if the line is a pure comment, then goto next
(if (TeX-in-commented-line)
(throw 'continue nil)
)
;; when you find one, back up to the beginning of the macro
(search-backward "\\")
;; If it's not at the beginning of the line, add a newline
(when (not (looking-back "^[ \t]*"))
(if (y-or-n-p "newline?")
(insert "\n")
)
)
;; move over the arguments, one or two pairs of matching braces
(search-forward "{") ; start of the argument
(forward-char -1)
(forward-sexp) ; move over the argument
(if (looking-at "[ \t]*{") ; is there a second argument?
(forward-sexp)
) ; move over it if so
(if (looking-at "[ \t]*\\[") ; is there a second argument?
(forward-sexp)
) ; move over it if so
(when (looking-at (concat "[ \t]*" (regexp-quote TeX-esc) "label"))
(goto-char (match-end 0))
(forward-sexp)
)
(if (looking-at (concat "[ \t]*%" ))
(throw 'continue nil)
)
;; If there is anything other than whitespace following the macro,
;; insert a newline
(if (not (looking-at "\\s *$"))
;;(insert "\n")
(if (y-or-n-p "newline (a)?")
(insert "\n")
)
)
) ; end catch 'continue
)
(LaTeX-fill-buffer 'left)
)
)

Answer 1

You could probably work up a single regexp and do a regexp replace for this. However, I find the logic of these manipulations becomes pretty hairy, particularly when you want to account for various edge-cases. In your example, you need to deal with some environments taking one argument, while others take two. I think it is easier to combine a series of simple regexps with basic text editing commands for this:
(defun enviro-split ()
"Find begin and end macros, and put them on their own line."
(interactive)
(save-excursion
(beginning-of-buffer)
;; loop over document looking for begin and end macros
(while (re-search-forward "\\\\\\(begin\\|end\\)" nil t)
;; when you find one, back up to the beginning of the macro
(search-backward "\\")
;; If it's not at the beginning of the line, add a newline
(when (not (looking-at "^"))
(insert "\n"))
;; move over the arguments, one or two pairs of matching braces
(search-forward "{") ; start of the argument
(forward-char -1)
(forward-sexp) ; move over the argument
(if (looking-at "\\s *{") ; is there a second argument?
(forward-sexp)) ; move over it if so
;; If there is anything other than whitespace following the macro,
;; insert a newline
(if (not (looking-at "\\s *$"))
(insert "\n")))))
This approach has the advantage of using Emacs' built-in functions for moving over sexps, which is much easier than coming up with your own regexp that can handle multiple, potentially nested, expressions inside braces.