fn merge_compatible_states()

in cli/src/generate/build_tables/minimize_parse_table.rs [113:189]

• 62 lines of code
• 5 McCabe index (conditional complexity)

    fn merge_compatible_states(&mut self) {
        let core_count = 1 + self
            .parse_table
            .states
            .iter()
            .map(|state| state.core_id)
            .max()
            .unwrap();

        // Initially group the states by their parse item set core.
        let mut group_ids_by_state_id = Vec::with_capacity(self.parse_table.states.len());
        let mut state_ids_by_group_id = vec![Vec::<ParseStateId>::new(); core_count];
        for (i, state) in self.parse_table.states.iter().enumerate() {
            state_ids_by_group_id[state.core_id].push(i);
            group_ids_by_state_id.push(state.core_id);
        }

        split_state_id_groups(
            &self.parse_table.states,
            &mut state_ids_by_group_id,
            &mut group_ids_by_state_id,
            0,
            |left, right, groups| self.states_conflict(left, right, groups),
        );

        while split_state_id_groups(
            &self.parse_table.states,
            &mut state_ids_by_group_id,
            &mut group_ids_by_state_id,
            0,
            |left, right, groups| self.state_successors_differ(left, right, groups),
        ) {
            continue;
        }

        let error_group_index = state_ids_by_group_id
            .iter()
            .position(|g| g.contains(&0))
            .unwrap();
        let start_group_index = state_ids_by_group_id
            .iter()
            .position(|g| g.contains(&1))
            .unwrap();
        state_ids_by_group_id.swap(error_group_index, 0);
        state_ids_by_group_id.swap(start_group_index, 1);

        // Create a list of new parse states: one state for each group of old states.
        let mut new_states = Vec::with_capacity(state_ids_by_group_id.len());
        for state_ids in &state_ids_by_group_id {
            // Initialize the new state based on the first old state in the group.
            let mut parse_state = ParseState::default();
            mem::swap(&mut parse_state, &mut self.parse_table.states[state_ids[0]]);

            // Extend the new state with all of the actions from the other old states
            // in the group.
            for state_id in &state_ids[1..] {
                let mut other_parse_state = ParseState::default();
                mem::swap(
                    &mut other_parse_state,
                    &mut self.parse_table.states[*state_id],
                );

                parse_state
                    .terminal_entries
                    .extend(other_parse_state.terminal_entries);
                parse_state
                    .nonterminal_entries
                    .extend(other_parse_state.nonterminal_entries);
            }

            // Update the new state's outgoing references using the new grouping.
            parse_state.update_referenced_states(|state_id, _| group_ids_by_state_id[state_id]);
            new_states.push(parse_state);
        }

        self.parse_table.states = new_states;
    }