[plt-scheme] simple macro

Eli,Joe,

Thanks for the help.

After Eli's message I decided to go with the
approach Joe's suggested.

Cheers
David

 -------------- Original message ----------------------
From: Joe Marshall <jrm at ccs.neu.edu>
> Eli Barzilay <eli at barzilay.org> writes:
> 
> >   For list-related administrative tasks:
> >   http://list.cs.brown.edu/mailman/listinfo/plt-scheme
> >
> > On Mar  2, David J. Neu wrote:
> >> 
> >>  (define-syntax init
> >>   (syntax-rules ()
> >>     ((_ sym def) (cond ((assq (quote sym) args) => cadr)
> >>                        (else def)))))
> 
> 
> > This will work:
> >
> >   (define-syntax (init stx)
> >     (syntax-case stx ()
> >       [(_ sym def)
> >        (with-syntax ([args (datum->syntax-object stx 'args stx)])
> >          #'(cond [(assq (quote sym) args) => cadr]
> >                  (else def)))]))
> 
> As will passing ARGS in to the macro:
> 
>  (define-syntax init
>    (syntax-rules ()
>      ((_ sym def args) (cond ((assq (quote sym) args) => cadr)
>                              (else def)))))
> 
>  (define f
>    (lambda (x . args)
>      (let  ((y (init y 2 args)))
>        (printf "x=~a y=~a~n" x y))))
> 
>