Re: how-many/count-matches for non-interactive use

[Luc Teirlinck]

Stefan Monnier wrote:

   Sit-for doesn't wait when executed from a macro.  As for messages you might
   be right in some (maybe even in many) cases but I doubt it matters much
   since unless the message is the last in the macro it will just be
   overwritten anyway.

If the macro is called with M-1000 or M-0, then, if nothing else, all
these messages might slow macro execution down.  Moreover, if there
are at least two different messages printed during execution of the
macro, it will also get rid of all previous info in *Messages*.

It is not clear to me whether we are currently discussing _changing_
the behavior of `interactive-p', or declaring it obsolete.  

I believe that changing it now would be very bad.  The current
behavior is very well documented in both the docstring and the Elisp
manual (and even in comments in the source code and such) and has been
in effect for a long time.  We can theoretically check all occurrences
in the Emacs tree (although there are tons of those), but we can not
possibly check all packages not included with the Emacs distribution.

On the other hand, there also is the problem that `interactive-p'
returns t while _defining_ a keyboard macro.  It would appear to be
deceiving to the user to have different behavior while _defining_ the
macro and while executing it.

I do not know what declaring a function obsolete _exactly_ means.  I
believe that what we could do is keep the function around indefinitely
in its current form, but discourage its use in new code meant for
inclusion in Emacs.  If people write their own functions for private
use, they might find interactive-p more convenient than the
alternative.  It also would mean that we would not have to worry about
checking all existing calls _right now_.

We could then recommend the following in the Elisp manual:

     (defun foo (&optional interactive-p)
       (interactive "p")
       (when interactive-p
         (message "foo")))

if the message needs to be printed even during keyboard
macro-execution and:

     (defun foo (&optional interactive-p)
       (interactive "p")
       (or (not interactive-p)
           executing-kbd-macro
           defining-kbd-macro
           (message "foo")))
 
if not.

Note that the behavior of the latter version of `foo' differs from the
current behavior of `interactive-p' by not showing the message during
macro definition either.

Sincerely,

Luc.