68 lines
2.2 KiB
Haskell
68 lines
2.2 KiB
Haskell
-- ghc-mod: Happy Haskell Hacking
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-- Copyright (C) 2015,2016 Daniel Gröber <dxld ÄT darkboxed DOT org>
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--
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-- This program is free software: you can redistribute it and/or modify
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-- it under the terms of the GNU Affero General Public License as published by
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-- the Free Software Foundation, either version 3 of the License, or
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-- (at your option) any later version.
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--
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-- This program is distributed in the hope that it will be useful,
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-- but WITHOUT ANY WARRANTY; without even the implied warranty of
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-- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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-- GNU Affero General Public License for more details.
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--
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-- You should have received a copy of the GNU Affero General Public License
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-- along with this program. If not, see <http://www.gnu.org/licenses/>.
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{-# LANGUAGE GeneralizedNewtypeDeriving, StandaloneDeriving #-}
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{-# LANGUAGE FlexibleInstances, UndecidableInstances #-}
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module Language.Haskell.GhcMod.Monad.State where
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import Language.Haskell.GhcMod.Types
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import Language.Haskell.GhcMod.Monad.Newtypes
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import Control.Monad
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import Control.Monad.State.Strict (StateT(..))
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import Control.Monad.Trans.Maybe (MaybeT(..))
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import Control.Monad.State.Class (MonadState(..))
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import Control.Monad.Trans.Class (MonadTrans(..))
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import Prelude
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class Monad m => GmState m where
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gmsGet :: m GhcModState
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gmsGet = gmsState (\s -> (s, s))
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gmsPut :: GhcModState -> m ()
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gmsPut s = gmsState (\_ -> ((), s))
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gmsState :: (GhcModState -> (a, GhcModState)) -> m a
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gmsState f = do
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s <- gmsGet
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let ~(a, s') = f s
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gmsPut s'
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return a
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{-# MINIMAL gmsState | gmsGet, gmsPut #-}
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instance GmState m => GmState (StateT s m) where
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gmsGet = lift gmsGet
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gmsPut = lift . gmsPut
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gmsState = lift . gmsState
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instance Monad m => GmState (StateT GhcModState m) where
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gmsGet = get
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gmsPut = put
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gmsState = state
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instance Monad m => GmState (GmT m) where
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gmsGet = GmT get
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gmsPut = GmT . put
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gmsState = GmT . state
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instance GmState m => GmState (MaybeT m) where
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gmsGet = MaybeT $ Just `liftM` gmsGet
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gmsPut = MaybeT . (Just `liftM`) . gmsPut
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gmsState = MaybeT . (Just `liftM`) . gmsState
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deriving instance (Monad m, GmState (GhcModT m)) => GmState (GmlT m)
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