[plt-scheme] problem with example macro

michael rice skrev:
> Noticed this about the first macro given in
> "Syntax-rules Primer for the Merely Eccentric" in the
> Macro section of schematics:cookbook.
> 
> Hope it's not something I'm doing wrong.
> 
> Michael
> 
> 
> (define-syntax nth-value
>   (syntax-rules ()
>     ((nth-value n values-producing-form)
>      (call-with-values
>        (lambda () values-producing-form)
>        (lambda all-values
>          (list-ref all-values n))))))
> 
> =================================
> 
> Welcome to DrScheme, version 360.
> Language: Swindle.
>> (nth-value 3 '(a b c d e f))
> . list-ref: index 3 too large for list: ((a b c d e
> f))


Your values-producing-form is '(a b c d e f).
That produces 1 value. This explains, why the
error say index 3 is too large.

Try

(nth-value 3 (values 'a 'b 'c 'd 'e 'f))

-- 
Jens Axel Søgaard