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Inspired by this answer, I have written the following function to perform a query-replace inside a math environment, but it does not work.

Edit. If you execute the function, the query-search tries to find all occurrences of string1, not necessarily those in math expressions, in other words texmathp is ignored.

Any hint to correct the code is welcomed. 

(defun my-query-replace-in-math (string1 string2)
  (interactive "Mfrom-string: \nMto-string: ")
  (while (and (query-replace string1 string2) (texmathp))))
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3
  • What does "it does not work" mean? Elaborate. Show us details.
    – phils
    Sep 12, 2019 at 12:46
  • @phils some explanations were added.
    – Name
    Sep 12, 2019 at 12:55
  • Use isearch-filter-predicate to ignore matches that don't satisfy texmathp. See the doc for that variable.
    – Drew
    Sep 12, 2019 at 14:15

1 Answer 1

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3

As suggested by @Drew, this can be achieved by setting isearch-filter-predicate appropriately. Indeed, the docstring for query-replace includes:

C-h f query-replace

...

Ignore read-only matches if ‘query-replace-skip-read-only’ is non-nil, ignore hidden matches if ‘search-invisible’ is nil, and ignore more matches using ‘isearch-filter-predicate’.

Here's a proposal allowing to toggle between "normal" and "math only" query replace:

(defun isearch-filter-visible-and-texmath (beg end)
  "Possible value for isearch-filter-predicate."
  (and (isearch-filter-visible beg end)
       (save-excursion (goto-char beg) (texmathp))))

(defun toggle-query-replace-in-maths ()
  "Toggle restricting query-replace to TeX math content."
  (interactive)
  (setq-local isearch-filter-predicate
              (if (eq isearch-filter-predicate #'isearch-filter-visible)
                  (progn
                    (message "Query replace now only in math")
                    #'isearch-filter-visible-and-texmath)
                (progn
                  (message "Query replace back to normal")
                  #'isearch-filter-visible))))

Note that setq-local is used so that the change is buffer local (it probably does not make sense for non tex buffers, anyway).

I don't find it totally satisfactory, since it will break other changes that could have been done to isearch-filter-predicate. Maybe someone will propose something better!

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4
  • Thank you for devoting time to provide this answer. I may have some comments after testing.
    – Name
    Sep 14, 2019 at 14:45
  • It is interesting that, when toggle-query-replace-in-maths in enabled, one can also do an isearch-forward (C-s) in math. The only inconvenience is that, when something is found, the entire equation from its beginning until the found term is highlighted. To see what I mean do a C-s for n in $A_{n}(X_1,\ldots,X_n)=0$, then press C-s again.
    – Name
    Sep 15, 2019 at 15:02
  • @Name isearch-forward being affected is not unexpected, given the name of the variable, but the highliting is indeed annoying. This needs more investigation!
    – JeanPierre
    Sep 18, 2019 at 19:30
  • I've been struggling with this problem for a long time and I was very happy to find this very elegant solution! Thank you very much!! However I found a litthe glitch, probably within texmathp, which prevents proper behavior when replacing within a construct I often use in TeX, namely $$ long equation $$$$ long equation continued $$. The second math environment is not recognized as such, unless I use a space between the 4.th and 5.th dollar sign.
    – Ruy
    Oct 8, 2022 at 1:44

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