Matthias Fischmann wrote:
now i want to create a list of a type similar to
[r1, r2, r3] :: (Resource a) => [a]
but with r1 being pizza, r2 being crude oil, and so on.
The type you actually want here is [exists a. (Resource a) && a], but no
Haskell implementation supports that.
data Rs = forall a . (Resource a) => Rs a
unRs (Rs a) = a
rsName :: Rs -> String
rsName = resourceName . unRs
...
[...]
but what is the type of unRs?
Its type is (Rs -> (exists a. (Resource a) && a)), but again no Haskell
implementation supports that.
-- Ben
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