{-# LANGUAGE ScopedTypeVariables #-}
module Rvarsample where {
import qualified System.Random as Random;
import Data.Random.Internal.Source(GetPrim(GetPrim));
import Control.Monad.State.Lazy(evalState,State); -- lazy state monad also works
import qualified Data.Random as Randomfu;
import Data.Random.Source.StdGen(getRandomPrimFromRandomGenState);
import Data.Function((&));

-- at least one of the GetPrim type annotations is required
rvarsample :: forall a gentype . (Random.RandomGen gentype) => gentype -> Randomfu.RVar a -> a;
rvarsample gen r = (GetPrim getRandomPrimFromRandomGenState :: GetPrim (State gentype))
& (Randomfu.runRVar r :: GetPrim (State gentype) -> State gentype a)
& ((\state -> evalState state gen) :: State gentype a -> a);
}