module Pipes.Misc.State.Lazy where
import Control.Lens
import Control.Monad.Reader
import Control.Monad.State.Lazy
import qualified Pipes as P
import qualified Pipes.Prelude as PP
store :: MonadState s m => Getter a b -> Setter' s b -> P.Pipe a a m r
store v s = forever $ do
a <- P.await
s .= view v a
P.yield a
retrieve :: MonadState s m => Getter s b -> P.Pipe a (b, a) m r
retrieve v = forever $ do
a <- P.await
s <- get
P.yield (view v s, a)
retrieve' :: MonadState s m => Getter s b -> P.Pipe () b m r
retrieve' v = forever $ do
P.await
s <- get
P.yield (view v s)
onState :: (MonadState s m) => (s -> m ()) -> P.Pipe a a m r
onState f = PP.mapM $ \a -> do
s <- get
f s
pure a