Re: Example use of macro to minimize and generalize the code

[Jean Louis <bugs@gnu.support>]

* Yuri Khan <yuri.v.khan@gmail.com> [2021-06-01 20:12]:
> On Tue, 1 Jun 2021 at 23:38, Jean Louis <bugs@gnu.support> wrote:
> 
> > > > (defmacro when-tabulated-id (table &rest body)
> > > >   (declare (indent 2) (debug t))
> > > >   ;;(ignore id)
> > > >   `(if id
> 
> > > Why don't you consider to make the id a real argument?
> >
> > I wish I could fully understand but I don't, and I consider your
> > advises important.
> >
> > How would I make the ID a real argument?
> 
> I believe Michael is hinting at this:
> 
>     (defmacro when-tabulated-id (id table &rest body)
>       `(if ,id
>            …
> 
> which means “at macro expansion time, substitute the value of the
> argument to the macro”, rather than your original
> 
>     (defmacro when-tabulated-id (id table &rest body)
>       `(if id
>            …
> 
> which means “at evaluation time, substitute the value of the symbol
> 'id”.

I have removed `id' argument and now I have:

(macroexpand '(when-tabulated-id "people" (ignore))) 
⇒ (if id (progn (ignore)) 
    (if (or (eq "people" 'any) (string-equal "people" rcd-current-table)) 
	(let ((id (tabulated-list-get-id)))
	  (if id (progn (ignore)) (message "Did not get ID"))) 
      (message "This function is for table `%s' only" "people")))

If I would use ,d it would expand into number or nil, it seem it would end up same.

Now I don't have compiler warnings, and functions work fine.

Let me know if I am making errors in this.

-- 
Jean

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