[racket] Port of Plot collection to TR

I think this should do it:

   (define-type (Listof* A) (Rec T (U A (Listof T))))
   (define-type Renderer-Tree (Listof* (U renderer2d nonrenderer)))

Neil ⊥

On 08/09/2012 01:56 PM, Ray Racine wrote:
> I could try and and seed a few things out of plot into TR that I have an
> immediate need for.   require/typed, optional args, opaque, typing Snips
> as Class ... I can handle.
>
> This one however ...
> Suggestions on how one would type the following?
>
> renderer-tree : (treeof (or/c renderer2d? nonrenderer?))
>
> On Thu, Aug 9, 2012 at 3:27 PM, Neil Toronto <neil.toronto at gmail.com
> <mailto:neil.toronto at gmail.com>> wrote:
>
>     On 08/09/2012 12:52 PM, Ray Racine wrote:
>
>         Noticed here
>         http://www.ccs.neu.edu/home/__samth/adapt/Current_Status.__html
>         <http://www.ccs.neu.edu/home/samth/adapt/Current_Status.html>
>
>
>     I had no idea someone had been assigned. Cool!
>
>
>         That the Plot collection still awaits porting to TR.  Has any
>         partial
>         work been done, maybe languishing in a github repo somewhere,
>         that can
>         be leveraged?
>
>
>     Are you volunteering? :)
>
>     It's only possible now that TR has support for keyword arguments.
>
>     There's one issue that could cause problems: some renderer-producing
>     functions, like `points', accept lists of vectors as arguments. If
>     the data argument to `points' had a nice, general type like
>
>         (Listof (Vectorof Real Real))
>
>     then applying `points' to
>
>         '(#(0.0 1.0) #(1.0 2.2))
>
>     wouldn't typecheck. The problem is that TR thinks `points' might
>     change that 0.0 to 0, which would make the original argument type
>     (Listof (Vector Float Float)) incorrect. It thinks Bad Things could
>     happen. (Technically, a vector is "invariant".)
>
>     I can think of two solutions right now:
>
>       1. Wait for a Const type constructor or similar.
>
>       2. Change the contract of `points' to accept lists of pairs,
>     sequences or a specialized data type.
>
>     I think the contract of `points' should be changed anyway, so users
>     can send it any kind of sequence. Might as well make it
>     current-TR-friendly at the same time.
>
>     Neil ⊥
>
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