philosophers.abs

// Written by Daniel Rødskog 2014
// http://www.mn.uio.no/ifi/english/research/groups/pma/completedmasters/2014/rodskog/

module Philosophers;

interface Philosopher { }

interface Fork {
    Unit grab(Philosopher owner);
    Unit release(Philosopher owner);
}


class Philosopher(Fork f1, Fork f2) implements Philosopher {

    Unit run() {
        while (True) {
            this.tell("is thinking");

            Fut<Unit> f;
            f = f1!grab(this);
            f.get;

            // await f1!grab(this);

            this.tell("grabbed left fork");

            // await f2!grab(this);
            f = f2!grab(this);
            f.get;

            this.tell("grabbed right fork");
            this.tell("is eating");

            f1!release(this);
            f2!release(this);

            this.tell("released both forks");
        }
    }

    Unit tell(String s) {
        Unit p = println(toString(this)+" "+s);
    }
}

class Fork implements Fork {
    Philosopher owner;

    Unit grab(Philosopher p) {
        await owner == null;
        owner = p;
    }

    Unit release(Philosopher p) {
        if (p == owner)
            owner = null;
    }
    
}


// MAIN //
{
    Fork f1 = new Fork();
    Fork f2 = new Fork();
    Fork f3 = new Fork();
    Fork f4 = new Fork();
    Fork f5 = new Fork();

    new Philosopher(f1, f2);
    new Philosopher(f2, f3);
    new Philosopher(f3, f4);
    new Philosopher(f4, f5);
    new Philosopher(f5, f1);
}