$~

($~) :: (HasGetter v, HasSetter v) => v a -> (a -> a) -> IO ()
OpenGL Graphics.Rendering.OpenGL.GL.StateVar
A modificator convenience function, transforming the contents of a state variable with a given funtion.
($~!) :: (HasGetter v, HasSetter v) => v a -> (a -> a) -> IO ()
OpenGL Graphics.Rendering.OpenGL.GL.StateVar
A variant of $~ which is strict in the transformed value.