GADTs in the wild

[Christian Maeder]

Am 14.08.2012 14:48, schrieb Felipe Almeida Lessa:
>    data AccessToken kind where
>        UserAccessToken :: UserId -> AccessTokenData -> UTCTime ->
> AccessToken UserKind
>        AppAccessToken  :: AccessTokenData -> AccessToken AppKind
>
>    data UserKind
>    data AppKind
>
> (Yes, that could be a data kind!)  And for convenience we also export
> some type synonyms:
>
>    type UserAccessToken = AccessToken UserKind
>    type AppAccessToken = AccessToken AppKind

Why not use plain h98?

   data UserAccessToken = UserAccessToken UserId AccessTokenData UTCTime
   data AppAccessToken = AppAccessToken AccessTokenData

   type AccessToken = Either UserAccessToken AppAccessToken

C.