[racket] Simplified scut-like macro

I think you should look at the Macro Stepper output for your failing
example, because you'll see that the code that references y appears in
the branch that doesn't have access to a y. You'd want to do something
in the macro to determine which function to compile to.

Jay

p.s. I'm glad you like super cut. =)

On 2/22/12, Paul Pereira <pjspereira at gmail.com> wrote:
> I am new to macro writing and am trying to do the following:
>
> (fun body ...)
>  =>  (lambda (x) body ...)
> or (lambda (x y) body ...)
> or (lambda (x y z) body ...)
>
> where x, y, z are taken from the scope of body.
> Right now, I am just trying to use case-lambda to switch between
> these. I guess I am trying for a much simpler version of scut (
> https://github.com/jeapostrophe/exp/blob/master/scut.ss ), but I don't
> understand that macro yet.
>
> What I have so far does not work:
>
> (define-syntax (fun stx)
>   (syntax-case stx ()
>     ((fun body rest ...)
>      (with-syntax ((x (datum->syntax #'body 'x))
>                    (y (datum->syntax #'body 'y))
>                    (z (datum->syntax #'body 'z)))
>         #'(case-lambda ((x) body rest ...)
>                        ((x y) body rest ...)
>                        ((x y z) body rest ...))))))
>
> (map (fun x) '(1 2 3))  => '(1 2 3)    ... ok
> (map (fun (+ x x)) '(1 2 3))  => '(2 4 6) ... ok
> (map (fun (+ x y)) '(1 2 3) '(1 2 3))  ... y is an unbound identifier
>
> Do you have any suggestions? Thanks!
>
> Paul
> ____________________
>   Racket Users list:
>   http://lists.racket-lang.org/users
>


-- 
Jay McCarthy <jay at cs.byu.edu>
Assistant Professor / Brigham Young University
http://faculty.cs.byu.edu/~jay

"The glory of God is Intelligence" - D&C 93