Re: replace-regexp from A to B?

[Yuri Khan <yurivkhan@gmail.com>]

On Sun, Aug 26, 2018 at 9:40 PM Rodolfo Medina <rodolfo.medina@gmail.com> wrote:

> Is it possible, and how?, to perform a replace-regexp from a certain point,
> e.g. the current one, or from a certain word/expression, up to the next
> occurrence of a certain other word/expression...?  In my case, with MusiXTeX
> documents, the starting point should be the TeX command `\startpiece' and the
> final one `\Endpiece'.  So I could replace strings/expressions within a single
> musical piece without going out of it.

I’d decompose the problem into two.

1. Mark the piece enclosing the point as a region.
2. Do an ordinary ‘replace-regexp’ or ‘query-replace-regexp’ in the region.

To solve (1), I’d first look if the major mode recognizes pieces as a
construct analogous to a function in a programming language, by
invoking ‘mark-defun’ and looking if it marks the whole piece. If it
does, problem solved; you can query-and-replace in current piece by
doing ‘C-M-h M-%’ or ‘C-M-h C-M-%’; or, if you want to do multiple
replacements in a piece, first narrow to it with ‘C-x n d’, then do
all your replacements, then widen back with ‘C-x n w’.

If the major mode does not have any useful notion of defun, I’d define
my own and arrange for it to be used by the major mode:

    (defun my-musixtex-beginning-of-piece (arg)
      (if (> arg 0)
          (dotimes arg (re-search-backward "\\\\startpiece\\>"))
        (dotimes (- arg) (re-search-forward "\\\\startpiece\\>"))))

    (defun my-musixtex-end-of-piece ()
      (re-search-forward "\\\\Endpiece\\>"))

    (defun my-musixtex-init-defun ()
      (setq-local beginning-of-defun-function
                  #'my-musixtex-beginning-of-piece)
      (setq-local end-of-defun-function
                  #'my-musixtex-end-of-piece))

    ;; change the mode hook variable name to suit your major mode
    (add-hook 'musixtex-mode-hook #'my-musixtex-init-defun)


If the major mode does have a useful idea of defun, I’d then just
write a function like this:

    (defun my-musixtex-mark-piece ()
      (interactive)
      (let* ((end (re-search-forward "\\\\Endpiece\\>"))
             (begin (search-backward "\\\\startpiece\\>")))
        (push-mark end nil t)
        (goto-char begin)))

and bind it to a convenient key probably involving the letter ‘h’ and
a few modifiers and/or prefix keys (because ‘mark-paragraph’ is on
‘M-h’, ‘mark-defun’ on ‘C-M-h’ and ‘mark-whole-buffer’ on ‘C-x h’).