I tried to do something simple using the rmonad package (attached).
I followed the example that's in haddocks (it is wrong, constraints has
no arguments), grabbed the list of extensions from rmonad's source, but
this program doesn't typecheck:
Could not deduce (Hashable a) arising from a use of `HM.singleton'
This seems to be an obvious use of this package ... am I missing something ?
{-# LANGUAGE MultiParamTypeClasses, TypeFamilies, ScopedTypeVariables, FlexibleInstances #-}
module Test where
import Control.RMonad.Prelude
import Data.Suitable (Constraints)
import qualified Data.HashMap.Strict as HM
import Data.Hashable (Hashable)
data MonadOutcome st = MonadOutcome { getOutcome :: HM.HashMap st Rational } deriving (Show)
data instance Constraints MonadOutcome a = (Hashable a, Eq a) => OutcomeConstraints
instance (Hashable a, Eq a) => Suitable MonadOutcome a where
constraints = OutcomeConstraints
instance RMonad MonadOutcome where
return x = MonadOutcome (HM.singleton x 1)
(>>=) = undefined
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