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 <pjspere...@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 <j...@cs.byu.edu> Assistant Professor / Brigham Young University http://faculty.cs.byu.edu/~jay "The glory of God is Intelligence" - D&C 93 ____________________ Racket Users list: http://lists.racket-lang.org/users
