Re: [External] : Re: function arguments optional default values

[Heime <heimeborgia@protonmail.com>]

On Saturday, July 6th, 2024 at 3:55 PM, Stefan Monnier via Users list for the GNU Emacs text editor <help-gnu-emacs@gnu.org> wrote:

> > > > Does elisp support function arguments optional default values ?
> > > > I solve that problem with following:
> > > > (defun my-function (arg &optional other-arg)
> > > > (let* ((other-arg (or other-arg my-default)))
> > > > other-arg))
> > > > Simpler - no reason for another binding,
> > > > just change the value (it's a local var).
> > 
> > (defun my-function (arg &optional other-arg)
> > (setq other-arg (or other-arg my-default))
> > ...)
> 
> 
> FWIW, assuming you're using `lexical-binding` (which you should), this
> tends to result in less efficient byte-code.
> 
> The difference is marginal in most cases (and efficiency of ELisp code
> is irrelevant in most cases as well), but the point is that bindings
> don't "cost" as much as mutation.

Does the mutation occur with 'setq' ?  And the binding is about the use of 
'let' and 'let*' ?  Then using the 'let' version would be preferred, right?