Why does replace-regexp backwards work so differently?

C-u - M-x replace-regexp \w+

The - prefix arg replaces backwards but it hits one char at a time, as if the plus sign weren’t there. The same replacement forwards (without the prefix arg) does hit one word at a time. What’s going on, @emacs@lemmy.ml?

  • SandraOP
    link
    fedilink
    1
    edit-2
    8 months ago

    So it’s literally looking at the regexp backwards and forwards at the same time 😵‍💫

    @0v0 @emacs

    • @0v0
      link
      18 months ago

      The regexp itself always looks forward, the BACKWARD argument just determines which direction the point should move after a match.

      • SandraOP
        link
        fedilink
        1
        edit-2
        8 months ago

        But what’s so weird is that replace-regexp forwards with \w+ replaces all words, while replace-regexp backwards with \w+ replaces the characters individually.

        @0v0 @emacs

        • @0v0
          link
          18 months ago

          Consider the string abc. From the end, moving backwards, when does it match \w+, and what does it match? When it reaches c, it matches c. And from the front, moving forwards? When it reaches a, it matches abc. This is why it acts differently.

          • SandraOP
            link
            fedilink
            38 months ago

            Yes, I got that, that wasn’t the weird part. The weird part is why the matcher is searching char-by-char backwards in the first place as opposed to skipping match-by-match.

            I’ll use “\b\w+”, that seems to work well. \W\w+ was not good since it caught the spaces.

            (Thanks for your patient repeated replies, BTW, I don’t mean to come across as ungrateful.)

            @0v0 @emacs