I make a lot of mistakes when I write prose, because I usually write down everything that comes to mind and then edit sentences and paragraphs over and over again until I get what I want. This is a recipe for all sort of errors, of course.

Although I have been a happy user of Flyspell and proselint, in order not to get distracted by warnings and errors nowadays I like to avoid automatic spell-checkers or linters and rely on ispell-buffer.

There is however a specific category of errors for which ispell-buffer cannot help: duplicate words. When quickly rephrasing a sentence or adjusting a paragraph it could happen that I do not pay enough attention to the words I remove and so I keep typing with no care whatsoever.

Much in the spirit of my occasional use of ispell-buffer, I want a command that scans the buffer, finds consecutive occurrences of the same word, and removes all but one of them. Emacs already has a built-in solution for this: C-M-% (query-replace-regexp).

Nevertheless, laziness prevails. Why typing the necessary regular expression every time when a simple command can do it for me?

(defun mu-delete-duplicate-words ()
  "Delete duplicate words via `query-replace-regexp'."
  (interactive nil text-mode)
    (goto-char (point-min))
    (query-replace-regexp "\\(\\b\\w+\\b\\)\\W+\\1\\b" "\\1")))