Transition Table

A transition table stores the next state for each state and event pair.

transition_table.c

#include <stdio.h>

enum DoorState {
    DOOR_CLOSED,
    DOOR_OPEN,
    DOOR_LOCKED
};

enum DoorEvent {
    EVENT_OPEN,
    EVENT_CLOSE,
    EVENT_LOCK
};

int main(void) {
    int event = ;
    int table[3][3] = {
        {DOOR_OPEN, DOOR_CLOSED, DOOR_LOCKED},
        {DOOR_OPEN, DOOR_CLOSED, DOOR_OPEN},
        {DOOR_LOCKED, DOOR_LOCKED, DOOR_LOCKED}
    };

    enum DoorState state = DOOR_CLOSED;
    state = (enum DoorState)table[state][event];

    printf("event=%d state=%d\n", event, state);
    return 0;
}

#include <stdio.h>

enum DoorState {
    DOOR_CLOSED,
    DOOR_OPEN,
    DOOR_LOCKED
};

enum DoorEvent {
    EVENT_OPEN,
    EVENT_CLOSE,
    EVENT_LOCK
};

int main(void) {
    int event = ;
    int table[3][3] = {
        {DOOR_OPEN, DOOR_CLOSED, DOOR_LOCKED},
        {DOOR_OPEN, DOOR_CLOSED, DOOR_OPEN},
        {DOOR_LOCKED, DOOR_LOCKED, DOOR_LOCKED}
    };

    enum DoorState state = DOOR_CLOSED;
    state = (enum DoorState)table[state][event];

    printf("event=%d state=%d\n", event, state);
    return 0;
}

#include <stdio.h>

enum DoorState {
    DOOR_CLOSED,
    DOOR_OPEN,
    DOOR_LOCKED
};

enum DoorEvent {
    EVENT_OPEN,
    EVENT_CLOSE,
    EVENT_LOCK
};

int main(void) {
    int event = ;
    int table[3][3] = {
        {DOOR_OPEN, DOOR_CLOSED, DOOR_LOCKED},
        {DOOR_OPEN, DOOR_CLOSED, DOOR_OPEN},
        {DOOR_LOCKED, DOOR_LOCKED, DOOR_LOCKED}
    };

    enum DoorState state = DOOR_CLOSED;
    state = (enum DoorState)table[state][event];

    printf("event=%d state=%d\n", event, state);
    return 0;
}

table Rows represent current states and columns represent events.

lookup One table lookup replaces a chain of repeated branch checks.