Nice. Thank you. On Thursday, July 19, 2012, Carl Eastlund <<a href="mailto:cce@ccs.neu.edu">cce@ccs.neu.edu</a>> wrote: > This works if you expand the use of Iteratee within the definition of > Continuation. Mutually-recursive polymorphic types are problematic, > but Continuation is only actually singly-recursive. You can still > have the definition Iteratee for outside use. > > Carl Eastlund > > #lang typed/racket/base > > ;; Inputs > (define-type (Stream D) (U (Datum D) 'Nothing 'EOS)) > (struct: (D) Datum ([iota : D])) > > ;; Iteratee > (define-type (Iteratee D A) (U (Done D A) (Continuation D A))) > (struct: (D A) Done ([accum : A] [stream : (Stream D)])) > (struct: (D A) Continuation ([resume : ((Stream D) -> (U (Done D A) > (Continuation D A)))])) > > > On Thu, Jul 19, 2012 at 6:07 PM, Ray Racine <<a href="mailto:ray.racine@gmail.com">ray.racine@gmail.com</a>> wrote: >> #lang typed/racket/base >> >> ;; Inputs >> (define-type (Stream D) (U (Datum D) 'Nothing 'EOS)) >> (struct: (D) Datum ([iota : D])) >> >> ;; Iteratee >> (define-type (Iteratee D A) (U (Done D A) (Continuation D A))) >> (struct: (D A) Done ([accum : A] [stream : (Stream D)])) >> (struct: (D A) Continuation ([resume : ((Stream D) -> (Iteratee D A))])) >> >> 1. How can I get the recursive nature of Iteratee and Continuation to type >> check? >> 2. Ideally, but not necessary, like to define Continuation as a >> define-struct/exec: >> >> Thanks, >> >> Ray >