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))))
  • What does "it does not work" mean? Elaborate. Show us details. – phils Sep 12 '19 at 12:46
  • @phils some explanations were added. – Name Sep 12 '19 at 12:55
  • Use isearch-filter-predicate to ignore matches that don't satisfy texmathp. See the doc for that variable. – Drew Sep 12 '19 at 14:15

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."
  (setq-local isearch-filter-predicate
              (if (eq isearch-filter-predicate #'isearch-filter-visible)
                    (message "Query replace now only in math")
                  (message "Query replace back to normal")

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!

| improve this answer | |
  • Thank you for devoting time to provide this answer. I may have some comments after testing. – Name Sep 14 '19 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 '19 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 '19 at 19:30

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