State Machine Implementations

Question

I am trying to build a board game ... And looks like it has to be implemented using a state machine..

I know of the State pattern from GoF, but I am sure there must be other ways to implement state machine. Please let me know.. if you know of any articles or books that contains details about different implementation (trade off of each of them), please direct me.. thanks

Answer 1

Check out Ragel.

Answer 2

We've used Harel's statecharts (similar/equivalent to state machines but somewhat easier to think about), there's a good book called Practical Statecharts in C/C++.

Answer 3

Here's a very simple FSM implementation:

public delegate void ProcessEvent<TEvent>(TEvent ev);

public abstract class StateMachine<TEvent>
{
    private ProcessEvent<TEvent> state;

    protected ProcessEvent<TEvent> State
    {
        get { return this.state; }
        set { this.state = value; }
    }

    public void ProcessEvent(TEvent ev)
    {
        this.state(ev);
    }
}

You would use it as follows:

public class MyFsm : StateMachine<byte>
{
    public MyFsm()
    {
        this.State = this.Started;
    }

    private void Started(byte ev)
    {
        Console.WriteLine(ev);

        if (ev == 255)
        {
            this.State = this.Stopped;
        }
    }

    private void Stopped(byte ev) { }
}

class Program
{
    static void Main(string[] args)
    {
        MyFsm fsm = new MyFsm();
        fsm.ProcessEvent((byte) 0);
        fsm.ProcessEvent((byte) 255);
        fsm.ProcessEvent((byte) 0);
    }
}

Answer 4

Finite State Machines provide the best platform to implement games which are all events driven.

Since your goal is to build the state machine you can use an existing framework and than all you need is to add your events extractors and actions.

One example framework can be seen at:

http://www.StateSoft.org