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Is there a way to cycle through \( x=1 \), \[ x=1\] and \begin{equation} x=1 \end{equation}

in any latex package? I find this function practical but I didn't know how to implement using elisp or maybe someone has already done that?

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3
  • I imagine I could write something to do this, but how would the function differentiate between math and some text that's simply in parens?
    – GJStein
    Jul 13, 2015 at 10:15
  • @GJStein sorry i forget to use double backslash to display backslash, maybe that is your question, because I never use dollar sign to start a math environment
    – seb
    Jul 13, 2015 at 10:27
  • Are you using AucTeX? If not, I'd recommend it. If so, there are some built in commands which would help out here.
    – GJStein
    Jul 13, 2015 at 13:58

1 Answer 1

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2

This function will do what you want:

(defun cycle-texmath () 

  (if (texmathp)
    (save-excursion
      (setq env (car texmathp-why))
      (if (string= env "equation") (progn 
        (search-backward "\\begin{equation}") (replace-match "\\[" t t)
        (search-forward "\\end{equation}") (replace-match "\\]" t t)))
      (if (string= env "\\[") (progn 
        (search-backward "\\[") (replace-match "\\(" t t)
        (search-forward "\\]") (replace-match "\\)" t t)))
      (if (string= env "\\(") (progn 
        (search-backward "\\(") (replace-match "\\begin{equation}" t t)
        (search-forward "\\)") (replace-match "\\end{equation}" t t)))
  )))

(eval-after-load "latex"
   '(progn
     (define-key LaTeX-mode-map (kbd "C-c t") (lambda () (interactive) (cycle-texmath)))
     ))

It relies on the texmathp and texmathp-why functions which are built into AucTeX to determine if the point is within a math mode and which indicators are used to invoke it. I've bound it to C-c t, but feel free to replace that with whatever you'd like.

EDIT:

After posing this as another question to handle the edge case of being within a text{} environment, the updated version of the code is here:

(defun cycle-texmath ()
  (save-excursion
    (while (member (TeX-current-macro) '("text"))
      (backward-char))
    (when (texmathp)
      (let ((env (car texmathp-why)))
        (cond
         ((string= env "equation")
          (search-backward "\\begin{equation}")
          (replace-match "\\[" t t)
          (search-forward "\\end{equation}")
          (replace-match "\\]" t t))
         ((string= env "\\[")
          (search-backward "\\[")
          (replace-match "\\(" t t)
          (search-forward "\\]")
          (replace-match "\\)" t t))
         ((string= env "\\(")
          (search-backward "\\(")
          (replace-match "\\begin{equation}" t t)
          (search-forward "\\)")
          (replace-match "\\end{equation}" t t)))))))
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  • Thanks you very much, it works exactly the way I want, and beside I learn some basic elisp buffer manip by looking at the code.
    – seb
    Jul 13, 2015 at 14:53
  • Well there is an issue with things like [xy=1 \text{ where (y=2)} ], but it is rare.
    – seb
    Jul 14, 2015 at 19:18
  • I posed this edge case as a (SO question)[emacs.stackexchange.com/questions/13988/…, and I've modified the code to handle it in accordance with the response. Be sure to upvote the correct answer there.
    – GJStein
    Jul 15, 2015 at 0:19
  • thanks a lot, in fact, I didn't state the edge case correctly. Actually when I am writing latex, frequently I need to change an inline math environment into display math, since it looks better; or sometimes I need to make a ref to some displayed equation, that's why changing \[\] into \begin{eq}etc is handy. So the question is, in a display math style like this \[ xy=1 \text{ where \(y=2\)}\], invoking cycle-math will produce \(xy=1 \text{ where \( y=2\) \) then comes to \begin{eq} \text{ where \( y=2 \end{eq} } \).
    – seb
    Jul 15, 2015 at 7:39

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