[plt-dev] dependent case-lambda contracts

I'd like to write a contract like this:

(case->
  (-> number? number?)
  (->d ([n number?] [s1 symbol?] [s2 (lambda (e) (eq? s1 e))]) () [_ number?]))

What's the best way to do this, since `case->' doesn't support `->d'?

Thanks,
-- 
sam th
samth at ccs.neu.edu