[racket] "variadic"nested for?

myfor is 'dynamic' in that it expands to the desired depth but yes, I need to know the number at compile time. 

The advantage is that I get a variable list of my choice 


On Mar 13, 2012, at 10:00 PM, rob cook wrote:

> Thanks - did not post reply properly - this is very useful, as is the prior example in a different way (yours does not seem to allow the list of iteration variables to be provided dynamically, e.g., as a list, the prior has no such list, but I can index into the values). Both can fit my needs though.
> 
> What a great user group!
> 
> Thanks again,
> Rob
> 
> On Tue, Mar 13, 2012 at 5:09 PM, Matthias Felleisen <matthias at ccs.neu.edu> wrote:
> 
> May I propose a slightly more useful macro instead:
> 
> #lang racket
> 
> (define-syntax (myfor stx)
>  (syntax-case stx ()
>    [(_ (i ...) for-clause todo ...)
>     #'(for* ([i for-clause] ...) todo ...)]))
> 
> (define (nestfortest . args) (displayln args))
> 
> (myfor (a b c) '(1 2)
>       (displayln `(,a ,b ,c)))
> 
> 
> 
> 
> On Mar 13, 2012, at 8:02 PM, rob cook wrote:
> 
> > To add to prior query - here's what I did, but I just think there *must* be a more elegant solution.
> >
> > (define (nestfor depth forclause todo)
> >   (define (nf depth forclause todo resultant)
> >     (for ((x forclause))
> >       (if (= depth 1)
> >           (apply todo (append (list x) resultant))
> >           (nf (- depth 1) forclause todo (append (list x) resultant)))))
> >   (nf depth forclause todo empty))
> >
> > (define (nestfortest . args) (displayln args))
> >
> > (nestfor 3 '(1 2) nestfortest)
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> 
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