-----------------------------------------------------------------------------
-- |
-- Module      :  Control.Monad.Indexed
-- Copyright   :  (C) 2008 Edward Kmett
-- License     :  BSD-style (see the file LICENSE)
--
-- Maintainer  :  Reiner Pope <reiner.pope@gmail.com>
-- Stability   :  experimental
-- Portability :  portable
--
----------------------------------------------------------------------------
module Control.Monad.Indexed
  ( IxFunctor(..)
  , IxPointed(..)
  , IxApplicative(..)
  , IxMonad(..)
  , IxMonadZero(..)
  , IxMonadPlus(..)
  , ijoin, (>>>=), (=<<<)
  , iapIxMonad
  ) where

import Data.Functor.Indexed

class IxApplicative m => IxMonad m where
  ibind :: (a -> m j k b) -> m i j a -> m i k b

ijoin :: IxMonad m => m i j (m j k a) -> m i k a
ijoin = ibind id

infixr 1 =<<<
infixl 1 >>>=

(>>>=) :: IxMonad m => m i j a -> (a -> m j k b) -> m i k b
m >>>= k = ibind k m

(=<<<) :: IxMonad m => (a -> m j k b) -> m i j a -> m i k b
(=<<<) = ibind

iapIxMonad :: IxMonad m => m i j (a -> b) -> m j k a -> m i k b
iapIxMonad f x = f >>>= \ f' -> x >>>= \x' -> ireturn (f' x')

class IxMonad m => IxMonadZero m where
  imzero :: m i j a

class IxMonadZero m => IxMonadPlus m where
  implus :: m i j a -> m i j a -> m i j a