incoming g s returns the symbol that labels the transition into state s. Returns None for initial states (which have no incoming transition). For non-initial states, returns Some sym where sym is the symbol that was parsed to reach this state.

items g s returns the set of LR(0) items in state s. These are the core items before closure is applied.

is_entrypoint g s returns Some prod if s is an initial state corresponding to an entrypoint, where prod is the pseudo (start) production for that entrypoint. Returns None for non-initial states.