(*=) :: State st s => Ref st s a -> (a->a) -> st s s ()
ref *= f = do v <- eval ref
              ref .= (f v)

{-
Records
-}
(*=) :: State st s => Ref st s a -> (a->a) -> st s s ()
ref *= f = do v <- eval ref
              ref .= (f v)

{-
Records
-}
ref *= f = do v <- eval ref
              ref .= (f v)

{-
Records
-}