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Add localReaderT to StreamK

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This commit is contained in:
Harendra Kumar 2024-01-28 10:26:03 +05:30
parent 76fc41fefd
commit 358e82cb32
1 changed files with 13 additions and 1 deletions
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14
core/src/Streamly/Internal/Data/StreamK/Transformer.hs
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@ -13,13 +13,16 @@ module Streamly.Internal.Data.StreamK.Transformer
, liftInner
, evalStateT
, localReaderT
)
where
import Control.Monad.Trans.Class (MonadTrans(lift))
import Control.Monad.Trans.State.Strict (StateT)
import Streamly.Internal.Data.StreamK.Type
(StreamK, nil, cons, uncons, concatEffect)
(StreamK(..), nil, cons, uncons, concatEffect, foldStream, mkStream)
import Control.Monad.Trans.Reader (ReaderT, local)
import qualified Control.Monad.Trans.State.Strict as State
@ -77,3 +80,12 @@ liftInner = go
case res of
Just (h, t) -> cons h (go t)
Nothing -> nil
-- | Modify the environment of the underlying ReaderT monad.
{-# INLINABLE localReaderT #-}
localReaderT :: (r -> r) -> StreamK (ReaderT r m) a -> StreamK (ReaderT r m) a
localReaderT f m =
mkStream $ \st yld sng stp ->
let single = local f . sng
yieldk a r = local f $ yld a (localReaderT f r)
in foldStream st yieldk single (local f stp) m