Re: [Emacs-diffs] master b88e7c8: Make transpose-regions interactive (Bug#30343)

[Karl Fogel <kfogel@red-bean.com>]

Richard Copley <rcopley@gmail.com> writes:
>I agree with Eli, it seems fine to me, but I'm not sure what the
>alternative is. If it's to move the body of the interactive spec into
>a function in an elisp file, and replace the spec with a call to that
>function, it seems overly complicated. (It also feel like a layering
>violation, but that can only be true if there is a rule or guideline
>saying so and I don't know of any.)

One solution would be to rename the C-defined function to Ftranspose_regions_internal (with no interactive spec), and move the entry point `transpose-regions' out to Lisp with the same interactive spec.  The Lisp function would just invoke `transpose-regions-internal'.

I'd be happy to do this, if there's consensus that it's a good solution.  

(I wrote the original non-interactive Ftranspose_regions, so am perhaps motivated by nostalgia.  Interestingly, while checking my memory to make sure, I discovered that although src/ChangeLog.4 has the correct record for 1994-04-29, in the git history that change is recorded as being authored by RMS -- commit b229b8d187a.  This suggests that there was some information lossage in a VC-system conversion somewhere along the way.  I don't know if we knew that already or not.)

I looked for all other C-defined functions that have a Lisp expression starting with "(" for their interactive spec in the DEFUN, i.e., are not just using the standard code-letter strings for `interactive'.  There appear to be a very small number of such functions:

  - Finsert_char
  - Ftranspose_regions
  - Frename_buffer
  - Fupcase_region
  - Fdowncase_region
  - Fdelete_file
  - Fset_file_modes

Of these, Ftranspose_regions is certainly the most complex, with Fdelete_file and Frename_buffer as runners up.  The others are relatively simple.  Maybe it's fine to just rely on our collective aesthetic judgement to say that the one in Ftranspose_regions is too complex to be tolerated, while the others are okay.

Best regards,
-Karl