/usr/lib/hugs/packages/base/Control/Monad/ST.hs is in libhugs-base-bundled 98.200609.21-5.3.
This file is owned by root:root, with mode 0o644.
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-- |
-- Module : Control.Monad.ST
-- Copyright : (c) The University of Glasgow 2001
-- License : BSD-style (see the file libraries/base/LICENSE)
--
-- Maintainer : libraries@haskell.org
-- Stability : experimental
-- Portability : non-portable (requires universal quantification for runST)
--
-- This library provides support for /strict/ state threads, as
-- described in the PLDI \'94 paper by John Launchbury and Simon Peyton
-- Jones /Lazy Functional State Threads/.
--
-----------------------------------------------------------------------------
module Control.Monad.ST
(
-- * The 'ST' Monad
ST, -- abstract, instance of Functor, Monad, Typeable.
runST, -- :: (forall s. ST s a) -> a
fixST, -- :: (a -> ST s a) -> ST s a
-- * Converting 'ST' to 'IO'
RealWorld, -- abstract
stToIO, -- :: ST RealWorld a -> IO a
-- * Unsafe operations
unsafeInterleaveST, -- :: ST s a -> ST s a
unsafeIOToST, -- :: IO a -> ST s a
unsafeSTToIO -- :: ST s a -> IO a
) where
import Prelude
import Control.Monad.Fix
import Data.Typeable
import Hugs.ST
import qualified Hugs.LazyST as LazyST
sTTc = mkTyCon "ST"; instance Typeable2 ST where { typeOf2 _ = mkTyConApp sTTc [] }; instance Typeable a => Typeable1 (ST a) where { typeOf1 = typeOf1Default }; instance (Typeable a, Typeable b) => Typeable (ST a b) where { typeOf = typeOfDefault }
realWorldTc = mkTyCon "RealWorld"; instance Typeable RealWorld where { typeOf _ = mkTyConApp realWorldTc [] }
fixST :: (a -> ST s a) -> ST s a
fixST f = LazyST.lazyToStrictST (LazyST.fixST (LazyST.strictToLazyST . f))
unsafeInterleaveST :: ST s a -> ST s a
unsafeInterleaveST =
LazyST.lazyToStrictST . LazyST.unsafeInterleaveST . LazyST.strictToLazyST
instance MonadFix (ST s) where
mfix = fixST
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