Emacs Redux

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A Peek at Emacs 24.4: Superword-mode

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In a previous post I wrote about camel-case aware editing with subword-mode. Emacs 24.4 adds a complementary minor mode called superword-mode, which also alters the behavior of word-based commands when enabled.

Normally Emacs would consider underscores and dashes word separators (snake_case and lisp-case anyone?). This affects all word commands - forward-word, backward-word, kill-word, etc. Let’s see a couple of examples (| denotes the cursor position):

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;; word with dash
|some-word

;; press M-f (forward-word) once
some|-word

;; press M-f again
some-word|

;; press M-b (backward-word) once
some-|word

;; word with underscore
|some_word

;; press M-f once
some|_word

;; press M-f again
some_word|

;; press M-b once
some_|word

;; word in camelCase (assuming subword-mode is not enabled)
|someWord

;; press M-f once
someWord|

;; word in camelCase (assuming subword-mode is enabled)
|someWord

;; press M-f once
some|Word

Personally I find the default behavior combined with subword-mode great. I do a lot of Ruby and Lisp programming and it also makes a lot of sense to me to be able to navigate the portions of a complex word, but I guess not everyone feels this way. Enter superword-mode - when it’s enabled all “complex/compound” words are treated as a single word:

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;; word with dash
|some-word

;; press M-f once
some-word|

;; word with underscore
|some_word

;; press M-f once
some_word|

;; word in camelCase
|someWord

;; press M-f once
someWord|

Note that you cannot have subword-mode and superword-mode enabled at the same time. Turning one of them on will disable the other.

Personally, I don’t see much value in superword-mode as a mode that’s enabled all the time, but I can imagine some useful scenarios in which I’d enable it briefly to do some focused editing.

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