withState

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.

Evaluate the inner monad of a stream using the supplied stateful runner function and the initial state. The state returned by an invocation of the runner is supplied as input state to the next invocation.

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.