Transient.Base

See http://github.com/agocorona/transient

The Monad

data TransIO x

Constructors

Transient

Fields

• runTrans :: StateT EventF IO (Maybe x)

Instances

Monad TransIO

Methods

(>>=) :: TransIO a -> (a -> TransIO b) -> TransIO b

(>>) :: TransIO a -> TransIO b -> TransIO b

return :: a -> TransIO a

fail :: String -> TransIO a

Functor TransIO

Methods

fmap :: (a -> b) -> TransIO a -> TransIO b

(<$) :: a -> TransIO b -> TransIO a

Applicative TransIO

Methods

pure :: a -> TransIO a

(<*>) :: TransIO (a -> b) -> TransIO a -> TransIO b

(*>) :: TransIO a -> TransIO b -> TransIO b

(<*) :: TransIO a -> TransIO b -> TransIO a

MonadIO TransIO

Methods

liftIO :: IO a -> TransIO a

Alternative TransIO

Methods

empty :: TransIO a

(<|>) :: TransIO a -> TransIO a -> TransIO a

some :: TransIO a -> TransIO [a]

many :: TransIO a -> TransIO [a]

MonadPlus TransIO

Methods

mzero :: TransIO a

mplus :: TransIO a -> TransIO a -> TransIO a

AdditionalOperators TransIO

Methods

(**>) :: TransIO a -> TransIO b -> TransIO b

(<**) :: TransIO a -> TransIO b -> TransIO a

atEnd' :: TransIO a -> TransIO b -> TransIO a

(<***) :: TransIO a -> TransIO b -> TransIO a

atEnd :: TransIO a -> TransIO b -> TransIO a

MonadState EventF TransIO

Methods

get :: TransIO EventF

put :: EventF -> TransIO ()

state :: (EventF -> (a, EventF)) -> TransIO a

(Num a, Eq a) => Num (TransIO a)

Methods

(+) :: TransIO a -> TransIO a -> TransIO a

(-) :: TransIO a -> TransIO a -> TransIO a

(*) :: TransIO a -> TransIO a -> TransIO a

negate :: TransIO a -> TransIO a

abs :: TransIO a -> TransIO a

signum :: TransIO a -> TransIO a

fromInteger :: Integer -> TransIO a

Monoid a => Monoid (TransIO a)

Methods

mempty :: TransIO a

mappend :: TransIO a -> TransIO a -> TransIO a

mconcat :: [TransIO a] -> TransIO a

type TransientIO = TransIO

Running the monad

keep :: Typeable a => TransIO a -> IO (Maybe a)

Keep the main thread running, initiate the non blocking keyboard input and execute the transient computation.

It also read a slash-separated list of string that are read by option and input as if they were entered by the keyboard

 foo  -p  options/to/be/read/by/option/and/input

keep' :: Typeable a => TransIO a -> IO (Maybe a)

Same than keep but do not initiate the asynchronous keyboard input. Useful for debugging or for creating background tasks, as well as to embed the Transient monad inside another computation. It returns either the value returned by exit. or Nothing, when there is no more threads running

stop :: Alternative m => m stopped

A sinonym of empty that can be used in a monadic expression. it stop the computation and execute the next alternative computation (composed with <|>)

input

option :: (Typeable b, Show b, Read b, Eq b) => b -> String -> TransIO b

Install a event receiver that wait for a string and trigger the continuation when this string arrives.

input :: (Typeable a, Read a, Show a) => (a -> Bool) -> String -> TransIO a

Validates an input entered in the keyboard in non blocking mode. non blocking means that the user can enter also anything else to activate other option unlike option, wich watch continuously, input only wait for one valid response

exit :: Typeable a => a -> TransIO a

Force the finalization of the main thread and thus, all the Transient block (and the application if there is no more code)

Asynchronous operations

async :: IO b -> TransIO b

Variant of parallel that execute the IO computation once

waitEvents :: IO b -> TransIO b

Variant of parallel that repeatedly executes the IO computation without end

spawn :: IO a -> TransIO a

`spawn= freeThreads . waitEvents`

parallel :: IO (StreamData b) -> TransIO (StreamData b)

Return empty to the current thread and execute the IO action in a new thread. When the IO action returns, the transient computation continues with this value as the result The IO action may be re-executed or not depending on the result. So parallel can spawn any number of threads/results.

If the maximum number of threads, set with threads has been reached parallel perform the work sequentially, in the current thread. So parallel means that 'it can be parallelized if there are thread available'

if there is a limitation of threads, when a thread finish, the counter of threads available is increased so another parallel can make use of it.

The behaviour of parallel depend on StreamData; If SMore, parallel will excute again the IO action. With SLast, SDone and SError, parallel will not repeat the IO action anymore.

sample :: Eq a => IO a -> Int -> TransIO a

Executes an IO action each certain interval of time and return his value if it changes

react :: Typeable eventdata => ((eventdata -> IO response) -> IO ()) -> IO response -> TransIO eventdata

De-invert an event handler.

The first parameter is the setter of the event handler to be deinverted. Usually it is the primitive provided by a framework to set an event handler

the second parameter is the value to return to the event handler. Usually it is `return()`

it configures the event handler by calling the setter of the event handler with the current continuation

State management

setState :: (MonadState EventF m, Typeable a) => a -> m ()

Synonym for setData

setData :: (MonadState EventF m, Typeable a) => a -> m ()

Set session data for this type. retrieved with getData or getSData Note that this is data in a state monad, that means that the update only affect downstream in the monad execution. it is not a global state neither a per user or per thread state it is a monadic state like the one of a state monad.

getState :: Typeable a => TransIO a

Synonym for getSData

getSData :: Typeable a => TransIO a

getData specialized for the Transient monad. if Nothing, the monadic computation does not continue.

If there is no such data, getSData silently stop the computation. That may or may not be the desired behaviour. To make sure that this does not get unnoticed, use this construction:

 getSData <|> error "no data"

To have the same semantics and guarantees than get, use a default value:

getInt= getSData <|> return (0 :: Int)

The default value (0 in this case) has the same role than the initial value in a state monad. The difference is that you can define as many get as you need for all your data types.

To distingish two data with the same types, use newtype definitions.

getData :: (MonadState EventF m, Typeable a) => m (Maybe a)

Get the state data for the desired type if there is any.

delState :: (MonadState EventF m, Typeable a) => a -> m ()

delData :: (MonadState EventF m, Typeable a) => a -> m ()

modifyData :: (MonadState EventF m, Typeable a) => (Maybe a -> Maybe a) -> m ()

Modify state data. It accept a function that get the current state (if exist) as parameter. The state will be deleted or changed depending on function result

modifyState :: (MonadState EventF m, Typeable a) => (Maybe a -> Maybe a) -> m ()

Synonym for modifyData

try :: TransIO a -> TransIO a

Executes the computation and reset the state if it fails.

Thread management

threads :: Int -> TransIO a -> TransIO a

Set the maximun number of threads for a procedure. It is useful to limit the parallelization of transient code that uses parallel spawn and waitEvents

addThreads :: Int -> TransIO ()

Assure that at least there are n threads available

freeThreads :: TransIO a -> TransIO a

The threads generated in the process passed as parameter will not be killed by `kill*` primitives.

Since there is no thread control, the application run slightly faster.

hookedThreads :: TransIO a -> TransIO a

The threads will be killed when the parent thread dies. That is the default. This can be invoked to revert the effect of freeThreads

oneThread :: TransIO a -> TransIO a

Delete all the previous child threads generated by the expression taken as parameter and continue execution of the current thread.

killChilds :: TransIO ()

kill all the child threads of the current thread

Additional operators

(**>) :: AdditionalOperators m => m a -> m b -> m b

Executes the second operand even if the frist return empty. A normal imperative (monadic) sequence uses the operator (>>) which in the Transient monad does not execute the next operand if the previous one return empty.

(<**) :: AdditionalOperators m => m a -> m b -> m a

Forces the execution of the second operand even if the first stop. It does not execute the second operand as result of internal events occuring in the first operand. Return the first result

(<***) :: AdditionalOperators m => m a -> m b -> m a

Forces the execution of the second operand even if the first stop. Return the first result. The second operand is executed also when internal events happens in the first operand and it returns something

(<|) :: TransIO a -> TransIO b -> TransIO a

When the first operand is an asynchronous operation, the second operand is executed once (one single time) when the first completes his first asyncronous operation.

This is useful for spawning asynchronous or distributed tasks that are singletons and that should start when the first one is set up.

for example a streaming where the event receivers are acivated before the senders.

exceptions

onException :: Exception e => (e -> TransIO ()) -> TransIO ()

When a exception is produced anywhere after this statement, the handler is executed. | handlers are executed Last in first out.

cutExceptions :: TransientIO ()

stop the backtracking mechanism from executing further handlers

continue :: TransIO ()

Resume to normal execution at this point

Utilities

data StreamData a

Async calls

Constructors

SMore a

SLast a

SDone

SError SomeException

Instances

Read a => Read (StreamData a)

Methods

readsPrec :: Int -> ReadS (StreamData a)

readList :: ReadS [StreamData a]

readPrec :: ReadPrec (StreamData a)

readListPrec :: ReadPrec [StreamData a]

Show a => Show (StreamData a)

Methods

showsPrec :: Int -> StreamData a -> ShowS

show :: StreamData a -> String

showList :: [StreamData a] -> ShowS

genId :: MonadState EventF m => m Int

Generator of identifiers that are unique withing the current monadic sequence They are not unique in the whole program.