[racket] Capturing Procedures in Macros: Style Question

If your purpose is to have modules written in polynomial math, 
you could create a little domain-specific language from Racket.
Specifically, subtract +, -, *, and expt from Racket when you 
export and rename your poly-add as +, poly-sub as -, etc. That's 
a two-line specification. And your client modules are then written
in 

 #lang PolyMathRacket 

This might fit your needs better. 

Also check out syntax parameters: 

   http://docs.racket-lang.org/reference/stxparam.html?q=stxparam&q=syntax%20parameter

-- Matthias



On Jun 18, 2011, at 11:17 AM, Deren Dohoda wrote:

> Hi everyone,
> 
> I wrote a small polynomial math library. In it are operations like
> poly-add, poly-times, poly-expt, and poly-sub, performing the
> operations that should be obvious. In a language like C++, one might
> have defined a polynomial class and then, possibly, override the +, -,
> and * operators (and throw up about the expt operation). I'm not
> normally a fan of operator overloading in a language because I feel it
> obscures what's actually happening. But in a language like Racket,
> overloading for a particular scope can be explicit and it seems less
> like encryption and more like good sugar.
> 
> The macro I have is:
> (define-syntax using-poly-math
>  (λ(stx)
>    (syntax-case stx ()
>      ((_ exp exps ...)
>       (with-syntax ((+ (datum->syntax #'exp '+))
>                     (- (datum->syntax #'exp '-))
>                     (* (datum->syntax #'exp '*))
>                     (expt (datum->syntax #'exp 'expt)))
>         #'(let ((+ poly-add)
>                 (- poly-sub)
>                 (* poly-times)
>                 (expt poly-expt))
>             (begin exp
>                    exps ...)))))))
> 
> My understanding of macros which capture variables is poor, compounded
> by my also poor understanding of syntax-case, and in fact this was
> kind of ripped from a blog post (I believe Eli's). But with it:
>> (let ((p1 '(1 1)))
>    (using-poly-math
>     (+ p1 (expt p1 5))))
> '(1 5 10 10 6 2)
> 
> Which is nice and concise.
> 
> I have two questions:
> 1) Is this kind of capturing macro a bad style?
> 2) Is this macro correct for what I'm trying to do? Is it expressed poorly?
> 
> Thanks for any insight,
> Deren
> 
> _________________________________________________
>  For list-related administrative tasks:
>  http://lists.racket-lang.org/listinfo/users