Re: change $$ to equations with automatic labels

[Tassilo Horn]

Uwe Brauer <oub@mat.ucm.es> writes:

> I am using the following code
>
> (defun my-change-dollar-to-equation ()
>   (interactive)
>   (save-excursion
>   (replace-regexp "\\$\\$\\(\\(.\\|\n\\)*?\\)\\$\\$"
>                   "\\\\begin{equation}\\1\\\\end{equation}")))

I just want to mention that this command will shoot into your foot when
you execute it when point is inside a $$...$$ block.

> But realized it would be nice to have for every changed equation, a
> label. I tend to use reftex-label for that purpose. But to include the
> automatic labeling in that simple function is beyond me, I am afraid.
>
> Can any of the elips gurus help?

The `replace-regexp' docstring says:

--8<---------------cut here---------------start------------->8---
This function is usually the wrong thing to use in a Lisp program.
What you probably want is a loop like this:
  (while (re-search-forward REGEXP nil t)
    (replace-match TO-STRING nil nil))
which will run faster and will not set the mark or print anything.
--8<---------------cut here---------------end--------------->8---

That will also give you the chance to compose a custom TO-STRING
programmatically, e.g., something like

  (concat "\\label{eqn:" my-num "}\n" (match-string 1))

where you'd have to increment my-num in every iteration.

Getting the initial value of my-num based on the labels already in the
document and ensuring that no duplicate labels are added is left as an
exercise to the reader. ;-)

You could skip that complication by using labels of the form
\label{eqn:dollar-converted:<NUM>} in the hope that "dollar-converted"
is very unlikely to appear in the wild.

Bye,
Tassilo