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ABC、DEF, GHI, JKL、MNO
PQR、STU, VWX、YZ

How do I replace all , s with in the repeated pattern above?

The repeated pattern can be mapped with the regex below:

"^\\([A-Z]+、\\)\\(\\([A-Z]+\\), \\)+"

However, because the , is a subset of group \\2, even though it can be separated from its preceding letters in the regex,

enter image description here

there is no way to replace it using replace-regexp without some form of nested group code. Also, DEF, doesn't seem the match like GHI, and STU, with the regex.

(replace-regexp "^\\([A-Z]+、\\)\\(\\([A-Z]+\\), \\)+" "\\1\\2、")

What's the right way to do this, then?


Update:

@jue's answer below resulted in this:

failed result

2

In elisp you normally search for what you're looking for in a loop, potentially establishing sub-groups of interest, and then you act on the match data if the search succeeded. Here you can simply replace every , with within the subgroup.

(save-excursion
  (while (re-search-forward "^[A-Z]+、\\(\\(?:[A-Z]+, \\)+\\)" nil t)
    (goto-char (match-beginning 1))
    (let ((bound (match-end 1)))
      (while (search-forward "," bound t)
        (replace-match "、")))))

Edit: Or more simply:

(save-excursion
  (while (re-search-forward "^[A-Z]+、" nil t)
    (while (re-search-forward "\\=\\([A-Z]+\\), " nil t)
      (replace-match "\\1、 "))))

That \= construct anchors the match to the current position of point, so that only the intended sequence of cases will be matched for that loop. Other options are supplying a BOUND argument to the search, or using narrowing to temporarily limit the searchable text.


Also, DEF, doesn't seem the match like GHI, and STU, with the regex.

That's because re-builder was highlighting the text which was referred to by back-reference \2 (being the ultimate match for that repeated subgroup) differently to the rest of the text. Try adding more matches for that group in a line, and it will become more obvious.

  • What if there are commas behind PQR、STU, VWX、YZ which I do not want to touch? For this is a simplification of Chinese bibliographic citations, APA style. A full citation looks like this: 鄧天珍、史少華, 白云星、方北松 (2019). 玉門花海畢家灘棺板《晉律注》保護修復. 江漢考古, (S1), 26–30. , which roughly translates to PQR、STU, VWX、YZ (2019). Title. Journal, (issue), 26-30. – Sati Oct 11 '20 at 12:21
  • 1
    My answer was based on the case in your question. If you want to make more detailed replacements then the inner (while (search-forward ... might be a (while (re-search-forward with a more detailed search pattern, and you might be specifying a group in the replace-match call. As always in Emacs, read the help for the functions in question, or look them up in the manual. – phils Oct 11 '20 at 12:30
  • I've added a simpler approach with a nested regexp search. – phils Oct 11 '20 at 20:38

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