Re: Making a function than can only be used interactively

[Christopher Dimech]

> Sent: Friday, July 08, 2022 at 6:55 PM
> From: "Yuri Khan" <yuri.v.khan@gmail.com>
> To: "help-gnu-emacs" <help-gnu-emacs@gnu.org>
> Subject: Re: Making a function than can only be used interactively
>
> On Fri, 8 Jul 2022 at 13:31, Emanuel Berg <incal@dataswamp.org> wrote:
> 
> > > It does not matter for interactive use. [...] ‘&optional’
> > > comes into play if you use this function non-interactively,
> > > from Lisp
> >
> > No, it matters. One example how it matters is that optional
> > arguments defaults to nil.
> 
> You’re right, with an interactive specification that evaluates to a
> list it matters, because the list you return may or may not have as
> many arguments as the function takes.
> 
> My point was that in the specific case of a three-argument function
> and a three-item string-valued interactive specification, &optional
> does not matter for interactive use.


It looks as if the easiest understanding of mandatory versus optional
function arguments occurs when using a function interactively.

For the interactive case, it is quite complicated, depending on whether
the function uses code characters or a list.

My proposition would be to include the corresponding explanation on using
in either the "Emacs Lisp Reference Manual" or the "Introduction to Programming
in Emacs Lisp".