65 lines
1.4 KiB
Idris
65 lines
1.4 KiB
Idris
module Control.Monad.ST.Extra
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import public Control.Monad.ST
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import Data.IORef
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import Control.MonadRec
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%default total
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export %inline
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MonadRec (ST s) where
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tailRecM seed (Access rec) st f = MkST $ do
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let MkST io = f seed st
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case !io of
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Done res => pure res
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Cont seed2 prf vst =>
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let MkST io = tailRecM seed2 (rec seed2 prf) vst f in io
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public export
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interface HasST (0 m : Type -> Type -> Type) where
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liftST : ST s a -> m s a
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export %inline HasST ST where liftST = id
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public export
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record STErr e s a where
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constructor STE
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fromSTErr : ST s (Either e a)
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export
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Functor (STErr e s) where
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map f (STE e) = STE $ map f <$> e
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export
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Applicative (STErr e s) where
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pure x = STE $ pure $ pure x
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STE f <*> STE x = STE [|f <*> x|]
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export
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Monad (STErr e s) where
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STE m >>= k = STE $ do
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case !m of
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Left err => pure $ Left err
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Right x => fromSTErr $ k x
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export
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MonadRec (STErr e s) where
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tailRecM s (Access r) x k = STE $ do
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let STE m = k s x
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case !m of
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Left err => pure $ Left err
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Right (Cont s' p y) => fromSTErr $ tailRecM s' (r s' p) y k
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Right (Done y) => pure $ Right y
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export
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runSTErr : (forall s. STErr e s a) -> Either e a
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runSTErr ste = runST $ fromSTErr ste
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export %inline HasST (STErr e) where liftST = STE . map Right
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export
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stLeft : e -> STErr e s a
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stLeft e = STE $ pure $ Left e
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