Re: Arbitrary function: find the number(s) of expected arguments

[Paul Pogonyshev]

Eli Zaretskii wrote:

> > In the attached patch I modified `doc/lispref/functions.texi': text about

> > `subr-arity' is moved to a new section above about `func-arity' and

> > adapted as needed. `subr-arity' is still in the documentation, but I

> > replaced its description with an advice to use `func-arity' instead. Is

> > that enough?

> 

> It's enough, but in the future please also provide a NEWS entry, like

> the one I added.

>

> > Do you still need changelog entries? Long time since I committed

> > anything to Emacs, maybe you finally got rid of them (I hope)?

> 

> We no longer maintain ChangeLog files in the repository, but we do

> request commit log messages in the ChangeLog format, so please do

> provide them in the future.  (I wrote them for you this time.)

OK.

> I pushed the changes to the master branch, thanks.

Thank you.

> There's one potential issue left:

> 

>  (func-arity 'with-temp-buffer) => error-> Invalid function: with-temp-buffer

> 

> Is it possible to support macros as well?  If not, how about producing

> a more meaningful error message?

Well, according to `functionp' macros are not functions, so it's

sort of correct.  On the other hand, it seems (symbol-function ...)

works, returning ('macro . FUNCTION) for them.  However, I can't

find any real C-level way to handle macros, e.g. `macrop' is even

not a builtin.

Or is just treating them as lists fine?  If so, we could add

something like this (untested):

diff --git a/src/eval.c b/src/eval.c

index 64a6655..5c594b8 100644

--- a/src/eval.c

+++ b/src/eval.c

@@ -2958,6 +2958,9 @@ function with `&rest' args, or `unevalled' for a special form.  */)

       && (function = XSYMBOL (function)->function, SYMBOLP (function)))

     function = indirect_function (function);

 

+  if (CONSP (function) && EQ (XCAR (function), Qmacro))

+    function = XCDR (function);

+

   if (SUBRP (function))

     result = Fsubr_arity (function);

   else if (COMPILEDP (function))

However, I'm not exactly sure what will happen with autoloaded

macros.

Paul