[r6rs-discuss] Why can ... and _ not be literals?

[David Van Horn]

On Sun, 24 Jun 2007, AndrevanTonder wrote:
> There are advantages in [allowing ... as a literal], though.  Here is
> the germ of a simple pattern matcher (not tested):
> 
>     (define-syntax matches?
>       (syntax-rules (...)
>         ((_ x ())
>          (null? x))
>         ((_ x (y ...))
>          (and (list? x)
>               (forall? (lambda (z) (matches? z y))
>                        x)))
>         ((_ x (y . z))
>          (and (pair? x)
>               (matches? (car x) y)
>               (matches? (cdr x) z)))
>         ((_ x id) #t)))
> 
>     (matches? '((1 2) (3 4 5))
>        ((x ...) ...))     ==> #t
> 
> It seems a pity to force someone to use syntax-case for this kind of thing
> when syntax-rules would otherwise be adequate.

Agreed.

David