= do { state1 <- getState
; ((), state2) <- withState code (state1 { cgs_tops = nilOL })
; setState $ state2 { cgs_tops = cgs_tops state1 }
= do { state1 <- getState
; ((), state2) <- withState code (state1 { cgs_tops = nilOL })
; setState $ state2 { cgs_tops = cgs_tops state1 }