    {-# LANGUAGE RankNTypes #-}

    -- We export this stuff separately so we don't clutter up the
    -- API of the Graphics.Gloss module.

    -- | Simulate mode is for producing an animation of some model who's picture
    --   changes over finite time steps. The behavior of the model can also depent
    --   on the current `ViewPort`.
    module Graphics.Gloss.Interface.IO.Simulate
            ( module Graphics.Gloss.Data.Display
            , module Graphics.Gloss.Data.Picture
            , module Graphics.Gloss.Data.Color
            , simulateIO
            , ViewPort(..))
    where
    import Graphics.Gloss.Data.Display
    import Graphics.Gloss.Data.Picture
    import Graphics.Gloss.Data.Color
    import Graphics.Gloss.Data.ViewPort
    import Graphics.Gloss.Internals.Interface.Simulate
    import Graphics.Gloss.Internals.Interface.Backend

    simulateIO :: forall model
            .  Display               -- ^ Display mode.
            -> Color                 -- ^ Background color.
            -> Int                   -- ^ Number of simulation steps to take for each second of real time.
            -> model                 -- ^ The initial model.
            -> (model -> IO Picture) -- ^ A function to convert the model to a picture.
            -> (ViewPort -> Float -> model -> IO model)
                                     -- ^ A function to step the model one iteration. It is passed the
                                     --     current viewport and the amount of time for this simulation
                                     --     step (in seconds).
            -> IO ()

    simulateIO :: Display
    -> Color
    -> Int
    -> model
    -> (model -> IO Picture)
    -> (ViewPort -> Float -> model -> IO model)
    -> IO ()
    simulateIO = GLUTState
    -> Display
    -> Color
    -> Int
    -> model
    -> (model -> IO Picture)
    -> (ViewPort -> Float -> model -> IO model)
    -> IO ()
    forall model a.
    Backend a =>
    a
    -> Display
    -> Color
    -> Int
    -> model
    -> (model -> IO Picture)
    -> (ViewPort -> Float -> model -> IO model)
    -> IO ()
    simulateWithBackendIO GLUTState
    defaultBackendState