withState -package:streamly-core

withState f m executes action m on a state modified by applying f.

• withState f m = modify f >> m

>>> runPureEff $ withState 10 $ \st -> do
n <- get st
pure (s -> (2 * n, s))
(20,10)

>>> runPureEff $ withState 10 $ \st -> do
n <- get st
pure (s -> (2 * n, s))
(20,10)

withStateT f m executes action m on a state modified by applying f.

• withStateT f m = modify f >> m

withStateT f m executes action m on a state modified by applying f.

• withStateT f m = modify f >> m

Opens a prepared statement, executes an action using this statement, and closes the statement, even in the presence of exceptions.

Bracket prepare and finalize. Useful for stepping multiple times through a Statement

runPureEff $ withStateSource $ \source -> do
n <- newState source 5
total <- newState source 0

withJump $ \done -> forever $ do
n' <- get n
modify total (+ n')
when (n' == 0) $ jumpTo done
modify n (subtract 1)

get total
15

runPureEff $ withStateSource $ \source -> do
n <- newState source 5
total <- newState source 0

withJump $ \done -> forever $ do
n' <- get n
modify total (+ n')
when (n' == 0) $ jumpTo done
modify n (subtract 1)

get total
15

Set a flag in the parser to True before running a parser, then set the flag's value to False.

Iterator that can be used to split computation jobs, while using a stateful scheduler.

Run a stateful parser with some initial state on a text. See also: runTextParser, runJournalParser.