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The forward-sexp command in EMACS can be used to find the $ that closes an inline equation: if the point is before the $ that opens the equation, then forward-sexp moves the point after the closing $. This does the correct thing with nested equations: e.g., if the point is before $a + \text{b $c$}$, then forward-sexp moves the point past the entire equation. Is there a way to find the \) or \] that closes a \( and \[ with auctex, perhaps with texmathp or font-latex-match-math-env? This seems to be a bit tricky in EMACS as there is no way to store multi-char delimiters in a syntax table.

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I would not bother: $...$, as opposed to \(...\), is reliably robust in macro arguments and when written to files (i.e., table of contents), and \begin{equation*}...\end{equation*} (using amsmath package) is quite better visible. – user9588 Apr 19 '12 at 16:28
@DavidKastrup Are \( and \) preferable to $? – N.N. Apr 21 '12 at 11:37
As I already said: I would not bother with \( \) \[ \]. The theoretic gain of matched delimiters is not worth the price in editing support and loss of robustness in LaTeX. – user9588 Apr 22 '12 at 15:41
@DavidKastrup But many people use fixltx2e which redefines them as robust. – N.N. Apr 22 '12 at 16:25
@N.N. I finally saw this discussion today; it is precisely the lack of support for matching these delimiters in EMACS that has kept me using $ in LaTeX. I have some macros to quickly switch equations between inline and displayed that make critical use of forward-sexp. – Samuel Isaacson May 13 '12 at 18:05
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1 Answer

up vote 4 down vote

I have put together a function that might do what you want. It searches for the next LaTeX math delimiter – \(, \), \[ or \] – while ignoring comments and if is an opening delimiter it tries to find its matching delimiter.

(defun forward-latex-math ()
  "Move forward across the next LaTeX equation. It is meant work like `forward-sexp' but for LaTeX math delimiters."
  (interactive)
  (let ((count 1))
    ;; Search for either of the following \( \) \[ \]
    (re-search-forward-ignore-TeX-comments "\\\\(\\|\\\\)\\|\\\\\\[\\|\\\\]")
    (cond
     ;; If the search hits \(
     ((looking-back "\\\\(" (- (point) 2))
      (while (< 0 count)
        ;; Search for delimiters inside the equation
        (re-search-forward-ignore-TeX-comments "\\\\(\\|\\\\)")
        (if (looking-back "\\\\(" (- (point) 2))
            (setq count (1+ count))     ; If start of a nested level
          (setq count (1- count))))     ; If end of a nested level
      ;; Find the matching \)
      (re-search-forward "\\\\)" (eobp) t count))
     ;; If the search hits \[
     ((looking-back "\\\\\\[" (- (point) 2))
      (while (< 0 count)
        ;; Search for delimiters inside the equation
        (re-search-forward-ignore-TeX-comments "\\\\\\[\\|\\\\]")
        (if (looking-back "\\\\\\[" (- (point) 2))
            (setq count (1+ count))     ; If start of a nested level
          (setq count (1- count))))     ; If end of a nested level
      ;; Find the matching \]
      (re-search-forward "\\\\]" (eobp) t count)))))

(defun re-search-forward-ignore-TeX-comments (regexp)
  "Search for REGEXP and ignore TeX comments. Used by `forward-latex-math'."
  (re-search-forward regexp (eobp) t)
  ;; If in comment search to after it
  (while (TeX-in-comment)
    (forward-line)
    (re-search-forward regexp (eobp) t)))

To use it place it in your .emacs and run it by M-xforward-latex-math. If you want to use it often you might want to bind it to key.

Since I have just started to learn Lisp I am sure this code can improved in many ways. Please comment if you have any suggestions.

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This doesn't deal with commented-out delimiters correctly. It's not clear to me that these delimiters can be properly matched without reimplementing LaTeX. – Samuel Isaacson May 13 '12 at 17:52
@SamuelIsaacson How should it deal with commented out delimiters? – N.N. May 13 '12 at 17:59
This code matches \( % \) as a single unit, but it shouldn't; it should continue searching on the next line to find the closing \). – Samuel Isaacson May 13 '12 at 18:12
@SamuelIsaacson I have updated the function to ignore comments. Let me know if it does not work as you want. – N.N. May 15 '12 at 15:44

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