This is a library of interactive processes combinators, usable to define extensible keymaps.
(Inspired by the Parsec library, written by Koen Claessen)
The processes are:
- composable: in parallel using
<|>, in sequence using monadic bind.
- extensible: it is always possible to override a behaviour by combination of
<|>. (See also
<||for a convenient combination of the two.)
- monadic: sequencing is done via monadic bind. (leveraging the whole battery of monadic tools that Haskell provides)
The processes can parse input, and write output that depends on it.
The semantics are quite obvious; only disjunction deserve a bit more explanation:
p = (a , what happens if
b recognize the same
input (prefix), but produce conflicting output?
- if the output is the same (as by the PEq class), then the processes (prefixes) are "merged"
- if a Write is more prioritized than the other, the one with low priority will be discarded
- otherwise, the output will be delayed until one of the branches can be discarded.
- if there is no way to disambiguate, then no output will be generated anymore.
This situation can be detected by using
- data I ev w a
- data P event w
- data InteractState event w
- class (PEq w, Monad m, Alternative m, Applicative m, MonadPlus m) => MonadInteract m w e | m -> w e where
- class PEq a where
- deprioritize :: MonadInteract f w e => f ()
- (<||) :: MonadInteract f w e => f a -> f a -> f a
- (||>) :: MonadInteract f w e => f a -> f a -> f a
- option :: MonadInteract m w e => a -> m a -> m a
- oneOf :: (Ord event, MonadInteract m w event) => [event] -> m event
- processOneEvent :: PEq w => P event w -> event -> ([w], P event w)
- computeState :: PEq w => P event w -> InteractState event w
- event :: (Ord event, MonadInteract m w event) => event -> m event
- events :: (Ord event, MonadInteract m w event) => [event] -> m [event]
- choice :: MonadInteract m w e => [m a] -> m a
- mkAutomaton :: PEq w => I ev w a -> P ev w
- idAutomaton :: (Ord a, PEq a) => P a a
- runWrite :: PEq w => P event w -> [event] -> [w]
- anyEvent :: (Ord event, MonadInteract m w event) => m event
- eventBetween :: (Ord e, MonadInteract m w e) => e -> e -> m e
- accepted :: Show ev => Int -> P ev w -> [[String]]
Interactive process description
Operational representation of a process
Abstraction of the automaton state.
Abstraction of monadic interactive processes
Outputs a result.
Consumes and returns the next character. Fails if there is no input left, or outside the given bounds.
option x p will either parse
p or return
x without consuming
Parses and returns the specified character.
Parses and returns the specified list of events (lazily).