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 <[email protected] <mailto:[email protected]>> 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 ⊥ ____________________ Racket Users list: http://lists.racket-lang.org/__users <http://lists.racket-lang.org/users>
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