{- | Module : Control.MonadOr.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.MonadOr.Graph where import Control.Graphted.Class import Control.MonadZero.Graph -- | Graph indexed monad with a monoidal operation satisfying the left catch law. -- -- See the typeclassopedia <https://wiki.haskell.org/Typeclassopedia>. class GMonadZero m => GMonadOr (m :: p -> * -> *) where -- | The or operation ('<|>') on the graph index. -- -- Default instance: @Or m i j = 'Combine' m i j@ type family Or m (i :: p) (j :: p) :: p type instance Or m i j = Combine m i j -- | An associative binary operation ('<|>'). gorelse :: m i a -> m j a -> m (Or m i j) a