Re: [Chicken-users] Aliasing a module variable with a variable from the user ?

[minh thu]

2007/3/29, Graham Fawcett <address@hidden>:
> On 3/29/07, minh thu <address@hidden> wrote:
> > Hi,
> >
> > Say I've a module with a bunch of procedures that use a global variable.
> > Call it *global*.
> >
> > Can I use that module and specify that *global* is an alias of *my-global* ?
> > (So that every procedures of the above module now work actually on 
> *my-global*.)

Hi Graham,

> It might be cleaner to use parameters instead:
>
> (define *global* (make-parameter #f))
>
> ;; set the value:
> (*global* *my-global*)   ; or whatever
>
> ;; use the value
> (print (+ 3 (*global*)))

That way, *my-global* is only readable via *global*.
But it's a good idea, I can set *global*, not to *my-global*, but to a
procedure to
read/write *my-global* (in fact, another parameter).

> If you're not familiar with parameters, it's worth a quick read of the
> docs (in short, they give you dynamic scoping instead of lexical
> scoping).

Well I just viewed them as an easy way to have globals.

> If you're going to the bother of rewriting all your *global*
> references to (*global*) instead, I suppose you could cheat and use
> (define-macro (*global*) '*my-global*) instead. But I'd use
> parameters.

Just before requiring the module ? I prefer the other way too, but it
might be a good idea.

Thank you,
thu