table.el, adding an option to customize escaping in latex export

[Pranshu <pranshusharma366@gmail.com>]

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diff --git a/lisp/textmodes/table.el b/lisp/textmodes/table.el
index 19c6a8d7c4..28401084a6 100644
--- a/lisp/textmodes/table.el
+++ b/lisp/textmodes/table.el
@@ -697,6 +697,19 @@ table-word-continuation-char
   :type 'character
   :group 'table)
 
+(defcustom table-source-latex-escape-characters (cons "[#$~_^%{}&]" t)
+  "A cons cell containing which charecters to escape in the latex source
+of `table-generate-source'.  The head of the list, if non-nil contains a
+regexp that matches all text that is to be adding a preceding backslash
+to the matching text. If nil, no non-backslash charecters will be
+escaped.  The tail, if non-nil, escapes all the backslashes in the latex
+source."
+  :tag "Source Latex Escape Charecters Regexp"
+  :type '(cons (radio (regexp :tag "regexp")
+                        (const :tag "Off" nil))
+               boolean)
+  :group 'table)
+
 (defcustom table-detect-cell-alignment t
   "Detect cell contents alignment automatically.
 When non-nil cell alignment is automatically determined by the
@@ -3264,19 +3277,29 @@ table--generate-source-scan-lines
                   (lambda (from to)
                     (let ((line (table--buffer-substring-and-trim
                                  (table--goto-coordinate (cons from y))
-                                 (table--goto-coordinate (cons to y)))))
+                                 (table--goto-coordinate (cons to y))))
+                          (escape-char-reg
+                           (apply 'concat (append (and (car table-source-latex-escape-characters)
+                                               (list "\\("
+                                                     (car table-source-latex-escape-characters)
+                                                     "\\)"
+                                                     (and (cdr table-source-latex-escape-characters)
+                                                          "\\|")))
+                                   (and (cdr table-source-latex-escape-characters)
+                                        (list"\\(\\\\\\)"))))))
                       ;; escape special characters
                       (with-temp-buffer
                         (insert line)
                         (goto-char (point-min))
-                        (while (re-search-forward "\\([#$~_^%{}&]\\)\\|\\(\\\\\\)\\|\\([<>|]\\)" nil t)
-                          (if (match-beginning 1)
-                              (save-excursion
-                                (goto-char (match-beginning 1))
-                                (insert  "\\"))
-                            (if (match-beginning 2)
-                                (replace-match "$\\backslash$" t t)
-                              (replace-match (concat "$" (match-string 3) "$")) t t)))
+                        (when (or (car table-source-latex-escape-characters)
+                                  (cdr table-source-latex-escape-characters))
+                          (while (re-search-forward escape-char-reg nil t)
+                            (if (and (car table-source-latex-escape-characters)
+                                     (match-beginning 1))
+                                    (save-excursion
+                                      (goto-char (match-beginning 1))
+                                      (insert  "\\"))
+                              (replace-match "$\\backslash$" t t))))
                         (setq line (buffer-substring (point-min) (point-max))))
                       ;; insert a column separator and column/multicolumn contents
                       (with-current-buffer dest-buffer

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When table.el tables are exported to latex, stuff like the dollar sign
is all escaped, so that you cannot make a table of latex equations.

This diff just adds a variable that works adding a variable that let's
the user control what is escaped and what is not.  Since backslashes
cannot be escaped the same way as charecters like '$', instead of making
2 vairbales( one for backslash and other for chars), I just added one
cons cell.

Instead of using string, I think using regexp better choice as it allows
for more complex escaping, such as turning mentions of "LaTeX" to
"\Latex".

Overall, this fixes the problem of being able to have column
wrapped paragraphs which include tex equations in some org exports.