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{-# OPTIONS_GHC -fno-warn-deprecations #-}
{-# LANGUAGE MultiParamTypeClasses, FunctionalDependencies #-}
module Foo where
-- This example suggested by Yitzchak Gale
import Control.Monad.State
import Control.Monad.Error
class Error e => Game b mv e | b -> mv e where
newBoard :: MonadState b m => m ()
-- This method is unambiguous, because
-- m determines b (via a fundep in MonadState)
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