Re: [Caml-list] GADTs and JSON

["Milan Stanojević" <milanst@gmail.com>]

You must have 'a in the input if you want to return 'a json (at least
a non-empty one). Same way you can't have function unit -> 'a list
that returns a non-empty list.

But it is probably not hard for you to create a witness type and have
that in input.
For example
eg get:(map : map json) -> key:string -> 'a witness -> 'a json option

You get None if key is not there or if it is not of the expected type.



On Thu, May 21, 2015 at 5:42 PM, Trevor Smith
<trevorsummerssmith@gmail.com> wrote:
> Hello,
>
> Is it possible to encode a recursive, heterogenous map and list
> datastructure with GADTs?
>
> I want to encode JSON (there are already a couple of great libraries out
> there so this is kind of an academic question). I would like to have
> functions that can only take a JSON map type, for example to take a json map
> and return a value. The key here is that the map can hold values of type
> int,string and also maps. Is this possible?
>
> eg get : (map : map json) -> key:string -> 'a json
>
> Thank you.
>
> Trevor