-- | Models an interface to a digital control, such as a valve or clutch.module Language.Atom.Common.DigitalControl  ( DigitalControl (..)  , digitalControl  , engage  , disengage  , isEngaged  , isDisengaged  ) whereimport Language.Atom-- | A DigitalControl is a control that can be either engaged or disengaged.data DigitalControl = DigitalControl (Var Bool)-- | Creates a 'DigitalControl' with a given name and initial state.digitalControl :: Name -> Bool -> System DigitalControldigitalControl name init = do  v <- bool name init  return $ DigitalControl v-- | Engages a DigitalControl.engage :: DigitalControl -> Action ()engage (DigitalControl v) = v <== true-- | Disengages a DigitalControl.disengage :: DigitalControl -> Action ()disengage (DigitalControl v) = v <== falseisEngaged :: DigitalControl -> Term BoolisEngaged (DigitalControl v) = value visDisengaged :: DigitalControl -> Term BoolisDisengaged = inv . isEngaged