Protesilaos Stavrou

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Emacs: introduction to 'substitute' (my new package?)

UPDATE 2023-01-16 19:13 +0200: I did add the package. Video demo here: https://protesilaos.com/codelog/2023-01-16-emacs-substitute-package-demo/.

I just set up the Git repositories of substitute for Emacs. Substitute is a set of commands that perform text replacement (i) throughout the buffer, (ii) limited to the current definition (per narrow-to-defun), (iii) from point to the end of the buffer, and (iv) from point to the beginning of the buffer.

These substitutions are meant to be as quick as possible and, as such, differ from the standard query-replace (which I still use). The provided commands prompt for substitute text and perform the substitution outright.

The substitution prompt mentions the target-to-be-substituted. It is possible to use the “future history” at this prompt (by typing M-n with the default key bindings for the next-history-element command). This populates the prompt with the text of the target. As such, if we want to operate on FOO to make it FOO-BAR, we use M-n and then append -BAR.

By default, the design is visually austere: the substitution prompt informs the user about the target but otherwise does not highlight anything. The post-substitution stage is also silent, with no report on how many occurences were replaced. This can be changed so that the substitution prompt highlights occurences (like isearch) and the post-substitution stage prints an informative message on what changed and where.

The substitution commands behave the same way except for their scope of application. What they have in common is the way they identify the target of the substitution: it is either the symbol at point or the text within the boundaries of the active region. The differences in scope are as follows:

  1. substitute-target-in-buffer: Substitute the target across the entire buffer.
  2. substitute-target-in-defun: Substitute the target only in the current definition (per narrow-to-defun).
  3. substitute-target-below-point: Substitute the target from point to the end of the buffer (alias substitute-target-to-end-of-buffer).
  4. substitute-target-above-point: Substitute the target from point to the beginning of the buffer (alias substitute-target-to-beginning-of-buffer).

Should this be on GNU ELPA?

I find these convenient, but I am not sure if I should formalise substitute as a package by adding it to GNU ELPA. What do others use for this case? I am aware of multiple-cursors and iedit but they are not what I am looking for. I also am still using query-replace for its interactivity (yes, I know about its ! operation) and for its ability to limit the effect to the region. I also know about combining embark with query-replace, which I also do. Still, I think there is a niche for substitute. Does anyone have the same feeling or am I deluding myself? In the latter case, there is no point in adding this to GNU ELPA.

You can contact me privately about this topic or, if you want a public discussion, use my “general issues” mailing list by sending an email to: ~protesilaos/general-issues@lists.sr.ht.

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