Search strings, do a list with first occurences and use elements of that list

Question

I have a LaTeX source, call it main.tex.

Suppose it contains one or more of the classical groups, like "GL", "SL", "SO", "U", "SU", "Sp", "USp" or the spin group "Spin".

I want to write a script that it inserts all the nedeed \DeclareMathOperator{}{} macros in a specified point of main.tex. That's to say, if main.tex contains, for instance, "GL", "SU" and "Spin", script will print in a specified point of main.tex

\DeclareMathOperator{\GL}{GL}
\DeclareMathOperator{\SU}{SU}
\DeclareMathOperator{\Spin}{Spin}

Here there is my code for one group:

(when (search-forward "\\GL" nil t)
  (setq gstring (match-string 0)) ;; this is group with backslash
  (setq gsubstring (substring gstring 1 nil)) ;; this is group without backslash
  (goto-char mypoint)
  (if (search-forward "\\DeclareMathOperator{\\GL}{GL}" nil t)
      nil
    (progn
      (insert "\\DeclareMathOperator{"
              gstring
              "}{"
              gsubstring
              "}"))
    ))

How can I generalize the above-mentioned code?

PS: I am not sure about title of my question. Any suggest?

Test 1

I have tried with StarBug suggestion. So:

(goto-char (point-min))

(setq mypoint (search-forward "\\begin{document}" nil t))

(defun test ()
  (interactive)

  (goto-char (point-min))

    (when (re-search-forward (rx (group (or "\\GL" "\\SL" "\\SO"))))
      (setq gstring (match-string 1)) ;; this is group with backslash
      (setq gsubstring (substring gstring 1 nil)) ;; this is group without backslash
      (goto-char mypoint)
      (if (search-forward (concat
               "\\DeclareMathOperator{"
               gstring
               "}{"
               gsubstring
               "}")
              nil t)
      nil
        (progn
      (goto-char mypoint)
          (insert "\\DeclareMathOperator{"
              gstring
              "}{"
              gsubstring
              "}"))
        ))
    )

I have tested this code on my main.tex:

%% BOF


\begin{document}


\GL

\SL

\SO


%% EOF

The code works without errors, buy it prints exclusively \DeclareMathOperator{\GL}{GL}. Do have I misunderstood?

Answer 1

Your Test 1 code has no iteration. It does one search and then terminates. Here is a modification with an iteration:

(defun test ()
  (interactive)
  (save-excursion
    (goto-char (point-min))
    (while (re-search-forward (rx (group (or "\\GL" "\\SL" "\\SO"))) nil t nil)
      (setq gstring (match-string 1)) ;; this is group with backslash
      (setq gsubstring (substring gstring 1 nil)) ;; this is group without backslash
      (if (not (test-is-operator-declared gsubstring))
      (save-excursion
        (goto-char mypoint)
            (insert "\\DeclareMathOperator{" gstring "}{" gsubstring"}\n"))))))

(defun test-is-operator-declared (arg)
  (save-excursion
    (goto-char (point-min))
    (search-forward (concat "\\DeclareMathOperator{\\" arg "}") nil t nil)))

Note the save-excursion commands, which ensure that point is not modified in the iteration.