{- | Module : Control.MonadPlus.Graph Description : Graph indexed monads with choice and failure Copyright : (c) Aaron Friel License : BSD-3 Maintainer : Aaron Friel <mayreply@aaronfriel.com> Stability : unstable Portability : portable -} {-# LANGUAGE DefaultSignatures #-} {-# LANGUAGE FlexibleContexts #-} {-# LANGUAGE MultiParamTypeClasses #-} {-# LANGUAGE PolyKinds #-} {-# LANGUAGE TypeFamilies #-} -- For the default Apply, Then, and But instances. {-# LANGUAGE UndecidableInstances #-} module Control.MonadPlus.Graph where import Control.Graphted.Class import Control.MonadZero.Graph class GMonadZero m => GMonadPlus (m :: p -> * -> *) where type family Plus m (i :: p) (j :: p) :: p type instance Plus m i j = Combine m i j gplus :: m i a -> m j a -> m (Plus m i j) a