Control.Monad.Supervisor

A supervisor monad that explore the execution tree of an internal monad and define extra behaviours thanks to flexible instance definitions for each particular purpose. It can inject new behaviours for backtracking, trace generation, testing, transaction rollbacks etc The supervisor monad is used in the package MFlow to control the routing, tracing, state management, back button management and navigation in general

Documentation

(!>) :: c -> String -> c

data Control a

The internal computation can be reexecuted, proceed forward or backward

Constructors

Control a

Forward a

Backward

Instances

Typeable1 Control

Read a => Read (Control a)

Show a => Show (Control a)

newtype Sup s m a

The supervisor add a Control wrapper that is interpreted by the monad instance

Constructors

Sup

Fields

runSup :: m (Control a)

Instances

Supervise s m => MonadState s (Sup s m)

MonadTrans (Sup s)

Supervise s m => Monad (Sup s m)

The Supervisor Monad is in essence an Identity monad transformer when executing Forward.

(MonadIO m, Supervise s m) => MonadIO (Sup s m)

class MonadState s m => Supervise s m where

The supervise class add two general modifiers that can be applied:

Methods

supBack

Arguments

:: s

-> m ()

Called before initiating backtracking in a control point When the computation goes back, by default the state is kepth. This procedure can change that behaviour. The state passed is the one before the computation was executed.

supervise

Arguments

:: s

-> m (Control a)

-> m (Control a)

When the conputation has been executed this method is an opportunity for modifying the result By default: supervise _= id

Instances

MonadState SessionData m => Supervise SessionData m

breturn :: Monad m => a -> Sup s m a

Flag the computation that executes breturn as a control point.

When the computation is going back, it will be re-executed (see the monad definition)