For the case:
(setq A ( 1 2 3 ))
There is no (efficient) way to find the symbol (1 2 3) is bound to. So
would you have to know the symbol all the time.
(de add-to-global-list (Sym Value)
(setq Sym (cons Value Sym)))
(de delete-from-global-list (Sym)
(setq Sym (cdr Sym)))
But i guess you do not want to pass the symbol around. But the function
still does need to what global symbol to work on. You can either use
Picolisp object system for that or you can implement it on your own.
(de return-list-handler (@Symbol)
(fill '((Op-code . Operands)
(cond
((= Op-code "add") (setq @Symbol (cons (car Operands) @Symbol)))
((= Op-code "sort") (setq @Symbol (sort @Symbol)))
((= Op-code "readcar") (car @Symbol))
((= Op-code "readcdr") (cdr @Symbol))
((= Op-code "del") (setq @Symbol (cdr @Symbol)))))))
You use it like that:
(setq c (return-list-handler '*Global-List))
(c "add" 1)
(c "add" 2)
(c "add" 3)
(c "add" 4)
*Global-List #-> (4 3 2 1)
(c "sort")
(c "readcar") #-> 1
I would really recommend you using objects though even though they are
basically the same under the hood.
Does that answer our question?
2016-12-17 22:01 GMT+01:00 Alexander Burger <a...@software-lab.de>:
> Hi Dean,
>
> On Sat, Dec 17, 2016 at 06:02:29PM +0000, dean wrote:
> > #{Is it possible to change a list AND keep it's name the same at
> different
> > program levels}#
> > (setq L '(a))
> > (de doit_temp (L) (prog (setq L (append L '(b))) (prinl "inside of fn L
> is
> > " L)) )
> > (de doit_perm (L) (setq NewL (append L '(b))))
> > (doit_temp L)
> > (prinl "outside of fn L is " L)
> > (doit_perm L)
> > (prinl "outside of fn NewL is " NewL)
> >
> > #inside of fn L is ab
> > #outside of fn L is a
> > #outside of fn NewL is ab
>
> Hmm, again I can't really understand what your question is. And you seem
> to use
> the wrong terminology.
>
> The key concept is "symbol binding". Let me try to clear some things up:
>
>
> > #{Is it possible to change a list AND keep it's name the same at
> different
> > program levels}#
>
> A list does not have a "name". You can only *bind* a symbol to a list.
>
> Binding is fundamental concept of Lisp, and you should *really* try to
> understand it thoroughly before writing any programs. Please study the
> example
> code in the distro and at rosettacode.org!
>
>
> > (setq L '(a))
>
> This binds the symbol 'L' globally to the list '(a)'.
>
>
>
> > (de doit_temp (L)
> > (prog
> > (setq L (append L '(b)))
> > (prinl "inside of fn L is " L) ) )
>
> (The 'prog' is not needed)
>
> The symbol 'L' is bound to some value when the function is called. Then it
> is
> extended by appending '(b)' to whatever value that is. That is printed,
> then 'L'
> is restored upon function return to whatever global value it had before.
>
>
> > (de doit_perm (L)
> > (setq NewL (append L '(b))) )
>
> 'NewL' is global from this function.
>
> It should be named *NewL according to the PicoLisp naming conventions.
>
>
>
> All this explains the output you get :)
>
> - Alex
> --
> UNSUBSCRIBE: mailto:picolisp@software-lab.de?subject=Unsubscribe
>
