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How to write an elisp function that transforms the word at point?

Specifically, in the C++ code I am refactoring I have to replace tons of raw pointers into smart pointers. Say, for class Foo, I would move point to the start of the word Foo, call my function, and obtain std::shared_ptr<Foo>.

So, the function I wish to implement would do these things:

  1. Move point to the beginning of the word.
  2. Insert hard-coded text (std::shared_ptr<).
  3. Go to the end of the word.
  4. Insert >.
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  • This question is likely a duplicate. Please search tag [query-replace] or tag [replace], and delete this question if you find it's a duplicate. Thx.
    – Drew
    Commented Oct 24, 2022 at 17:11
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    Of course, you could write and bind your own elisp command, but you might find it simpler to record, save and bind a keyboard macro.
    – dalanicolai
    Commented Oct 24, 2022 at 17:25
  • Sorry @Drew, I find your editing went a bit far. I do want to write an elisp macro. I do not want a complicated sequence of keystrokes which I have to remember and repeat anew in each session.
    – Joachim W
    Commented Oct 24, 2022 at 18:32
  • No, this has nothing to do with Elisp macros. Read the meaning of the tags. It sounds like you want a single key binding that does what you want. That's a keyboard macro or a command that's bound to a key. The meat of it is to make the change you want. How that's bound to a key is something else.
    – Drew
    Commented Oct 24, 2022 at 22:18
  • What Drew is talking about is that the word "macro" has two very different meanings in an emacs context. What you want is a keyboard macro which can automate repetitive key sequences. An elisp macro is a language construct that generates elisp code -- same word but very different meaning.
    – g-gundam
    Commented Oct 24, 2022 at 22:38

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Creating Reusable Keyboard Macros In Emacs

There is a concise article on how to use keyboard macros in Emacs that I recommend you read. The info in that article can be adapted to solve your specific problem like this:

  • Place your cursor on the 'F' in a variable declaration of type Foo.
  • Hit C-x ( to start recording a macro.
  • Type s t d : : s h a r e d _ p t r < C-right >
  • Hit C-x ) to stop recording the macro.
  • Hit M-x name-last-kbd-macro to give the macro you just created a name. For this example, I called it std-shared-ptr.
  • Open your emacs configuration file.
  • Type M-x insert-kbd-macro and tell it to insert std-shared-ptr. The end result should look like this.
(fset 'std-shared-ptr
   (kmacro-lambda-form [?s ?t ?d ?: ?: ?s ?h ?a ?r ?e ?d ?_ ?p ?t ?r ?< C-right ?>] 0 "%d"))

The fset function creates an interactive function named std-shared-ptr, and you can see what keys are going to be sent to Emacs by inspecting the vector it generated.

You can invoke this macro by hitting M-x std-shared-ptr, but if you're going to do this a lot, you might want to bind this to something that's easier to type. Also, we created this macro using Foo, but the C-right we hit while creating the macro should make it work for any type or class.

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    Instead of C-<right> (which is bound to right-word), I would recommend C-M-<right> (which is bound to forward-sexp): if the class name contains an underscore (which I iimagine is a a frequent occurrence), right-word would stop before the first underscore, wheres forward-sexp) would stop after the whole identifier. BTW, in my case, C-M-<right is preempted by my desktop environment, so I have to use <ESC> C-<right> instead.
    – NickD
    Commented Oct 26, 2022 at 12:27

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