Simulation.Aivika.Task

Tested with: GHC 8.0.1

The Task value represents a process that was already started in background. We can check the completion of the task, receive notifications about changing its state and even suspend an outer process awaiting the final result of the task. It complements the Process monad as it allows immediately continuing the main computation without suspension.

Task

data Task a

The task represents a process that was already started in background.

data TaskResult a

Represents the result of the task.

Constructors

TaskCompleted a

the task was successfully completed and it returned the specified result

TaskError IOException

the specified exception was raised when performing the task.

TaskCancelled

the task was cancelled

taskId :: Task a -> ProcessId

Return an identifier for the process that was launched in background for this task.

tryGetTaskResult :: Task a -> Event (Maybe (TaskResult a))

Try to get the task result immediately without suspension.

taskResult :: Task a -> Process (TaskResult a)

Return the task result suspending the outer process if required.

taskResultReceived :: Task a -> Signal (TaskResult a)

Return a signal that notifies about receiving the result of the task.

taskProcess :: Task a -> Process a

Return an outer process that behaves like the task itself, for example, when the task is cancelled if the outer process is cancelled.

cancelTask :: Task a -> Event ()

Cancel the task.

taskCancelled :: Task a -> Event Bool

Test whether the task was cancelled.

Running Task

runTask :: Process a -> Event (Task a)

Run the process in background and return the corresponding task immediately.

runTaskUsingId :: ProcessId -> Process a -> Event (Task a)

Run the process with the specified identifier in background and return the corresponding task immediately.

Spawning Tasks

spawnTask :: Process a -> Process (Task a)

Run a child process in background and return immediately the corresponding task.

spawnTaskUsingId :: ProcessId -> Process a -> Process (Task a)

Run using the specified identifier a child process in background and return immediately the corresponding task.

spawnTaskWith :: ContCancellation -> Process a -> Process (Task a)

Run a child process in background and return immediately the corresponding task.

spawnTaskUsingIdWith :: ContCancellation -> ProcessId -> Process a -> Process (Task a)

Run using the specified identifier a child process in background and return immediately the corresponding task.

Enqueueing Task

enqueueTask :: Double -> Process a -> Event (Task a)

Enqueue the process that will be started at the specified time from the event queue. It returns the corresponding task immediately.

enqueueTaskUsingId :: Double -> ProcessId -> Process a -> Event (Task a)

Enqueue the process that will be started at the specified time with the given identifier from the event queue. It returns the corresponding task immediately.

Parallel Tasks

taskParallelResult :: Task a -> Task a -> Process (TaskResult a, Task a)

Return the result of two parallel tasks.

taskParallelProcess :: Task a -> Task a -> Process (a, Task a)

Return an outer process for two parallel tasks returning the result of the first finished task and the rest task in pair.