Re: References/locations

[Maciek Godek]

Stephen Compall:

> Actually, if you (use-syntax (ice-9 syncase)), you should be able to
> define lexical symbol-macros that expand a single symbol, even in a
> set! place, something like:
>
> (define v #(1 2 3))
> (define-syntax v1
>  (lambda (stx)
>    (syntax-case stx ()
>      (_ v))))

I don't really get this syntax-rules. Do you know of any good tutorial?
[I find the description in the revised report too difficult to understand]

> Obviously aliasing will serve:
>
> (define-syntax alias-syntax
>  (syntax-rules ()
>    ((_ form)
>     (lambda (stx)
>       (syntax-case stx ()
>         (_ (syntax form)))))))
>
> (define-syntax defalias
>  (syntax-rules stx ()
>    ((_ new form)
>     (define-syntax new (alias-syntax form)))))

ERROR: invalid syntax (syntax-rules stx () ((_ new form)
(define-syntax new (alias-syntax form))))
 => error-in-evaluation
(That's what guile says)

> (define-syntax let-alias
>  (syntax-rules ()
>    ((_ ((new form) ...) body ...)
>     (let-syntax ((new (alias-syntax form)) ...) body ...))))
>
> (defalias v1 (vector-ref v 1))
>
> (set! v1 42)
> (vector-ref v 1) ; => 42

Could you explain it in more detail? Why should it work?
(Or at least give me a link with such explanations)

Thanks in advance
M.