[racket] How does free-identifier=? and bound-identifier=?works?

Your code also returne (#t #t)
Also see Ryan Culpepper's email.
Jos 

> -----Original Message-----
> From: users-bounces at racket-lang.org 
> [mailto:users-bounces at racket-lang.org] On Behalf Of Marco Maggi
> Sent: 10 April 2011 13:23
> To: Veer
> Cc: users at racket-lang.org
> Subject: Re: [racket] How does free-identifier=? and 
> bound-identifier=?works?
> 
> Veer wrote:
> > I  am  unable  to  understand  how  free-identifier=?  and
> > bound-identifier=? works?
> [...]
> > When I use them ,they both produces #t .
> 
> You are misunderstanding the  meaning of the function names;
> you may try  to read [1] which is  an annotated section from
> the R6RS standard.
> 
>   However,  your  true  misunderstanding  is to  think  that
> identifiers in the input form  of a macro transformer have a
> "meaning", for  example LET is  a binding syntax;  they have
> not: identifiers in an input form are just identifiers, they
> do  not affect the  binding of  other identifiers.   In your
> example:
> 
>   (check (lambda (x y) (let ([x 2]) x)))
> 
> the identifiers LAMBDA and LET  in the input form of the use
> of CHECK are "just identifiers",  they do not influence X in
> any way; only if you put  into the output form of CHECK they
> may behave  like the syntaxes  of the language (if  they are
> in the correct position).
> 
>   Also  notice that your  CHECK macro  (as I  understand it)
> does not do what  you want to do; to do what  you want to do
> you should (notice the use of #` and #,):
> 
> #!r6rs
> (import (rnrs))
> 
> (define-syntax check
>   (lambda (stx)
>     (syntax-case stx (lambda let)
>       [(_ (lambda (x y ...) (let ([a b]) c)))
>        #`(values #,(free-identifier=? #'x #'c)
>                  #,(bound-identifier=? #'x #'c))])))
> 
> (let-values (((r1 r2)
> 	      (check (lambda (x y) (let ([x 2]) x)))))
>   (write (list r1 r2))
>   (newline))
> 
> HTH
> 
> [1] 
> <http://marcomaggi.github.com/docs/nausicaa.html/stdlib-syntax
_002dcase-identifier.html>
> 
> P.S.  It takes time understand this stuff; also, some people
> think that  FREE-IDENTIFIER=? and BOUND-IDENTIFIER=?  are an
> unfortunate choice of names, which induces misunderstanding.
> -- 
> Marco Maggi
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