DiningPhil.pj

import std.*;

// void philosopher(int id, chan<boolean>.write left,
// 		 chan<boolean>.write right) {
//     while (true) {
// 	println(id + ": I am thinking");
// 	par {                // pick up forks
// 	    left.write(true);   
// 	    right.write(true);
// 	}
// 	println(id + ": I am eating");
// 	par {                // put down forks
// 	    left.write(true);
// 	    right.write(true);
// 	}
//     }
// }

void securePhilosopher(int id, chan<boolean>.write left,
		       chan<boolean>.write right,
		       chan<boolean>.write down,
		       chan<boolean>.write up) {
    while (true) {
	println(id + ": I am thinking");
	println(id + ": I want to sit down.");
 	down.write(true);    // ask to sit down
	par {                // pick up forks
	    left.write(true);   
	    right.write(true);
	}
	println(id + ": I am eating");
	par {                // put down forks
	    left.write(true);
	    right.write(true);
	}
	println(id + ": I want to get up.");
	up.write(true);      // get up
    }
}

// fork is a reserved word for now, so use Fork
void Fork(int i, chan<boolean>.read left,
	  chan<boolean>.read right) {
    boolean any;
    while (true) {
	alt {
	    any = left.read(): {   // right phil picks up
            println(i + ": picked up from the right."); 
            any = left.read();   // right phil puts down
            println(i + ": put down from the right."); 
	    }
	    any = right.read(): {  // left phil picks up
            println(i + ": picked up from the left."); 
            any = right.read();  // left phil puts down
            println(i + ": put down from the left.");      
	    }
	}
    }
}

void security(chan<boolean>.read[] up, chan<boolean>.read[] down) {
    // up.length does not cause an error! 
    const int maxSatDown = up.size - 1;
    int satDown = 0;
    boolean any;
    while (true) {
      println("Sat Down = " + satDown);
      alt {
	    (satDown < maxSatDown) && any = down[0].read(): satDown = satDown + 1;
	    (satDown < maxSatDown) && any = down[1].read(): satDown = satDown + 1;
	    (satDown < maxSatDown) && any = down[2].read(): satDown = satDown + 1;
	    (satDown < maxSatDown) && any = down[3].read(): satDown = satDown + 1;
	    (satDown < maxSatDown) && any = down[4].read(): satDown = satDown + 1;
	    any = up[0].read(): satDown = satDown - 1;
	    any = up[1].read():	satDown = satDown - 1;
	    any = up[2].read():	satDown = satDown - 1;
	    any = up[3].read():	satDown = satDown - 1;
	    any = up[4].read():	satDown = satDown - 1;
	    }
    }
}

void college() {    
    // I handcoded this for you - I didn't check I got
    // it right, so you may wanna check that yourself ;-)
    chan<boolean> left0, left1, left2, left3, left4;
    chan<boolean> right0, right1, right2, right3, right4;

    par {
        philosopher(0, left0.write, right0.write);
        philosopher(1, left1.write, right1.write);
        philosopher(2, left2.write, right2.write);
        philosopher(3, left3.write, right3.write);
        philosopher(4, left4.write, right4.write);
        
        Fork(0, left0.read, right1.read);
        Fork(1, left1.read, right2.read);
        Fork(1, left2.read, right3.read);
        Fork(1, left3.read, right4.read);
        Fork(2, left4.read, right0.read);
    }
}


void secureCollege() {
    // I handcoded this for you - I didn't check I got                                                                  
    // it right, so you may wanna check that yourself ;-)                                                               
    chan<boolean> left0, left1, left2, left3, left4;
    chan<boolean> right0, right1, right2, right3, right4;
    chan<boolean> down0, down1, down2, down3, down4;
    chan<boolean> up0, up1, up2, up3, up4;

    chan<boolean>.read[] ups = new chan<boolean>.read[5];
    chan<boolean>.read[] downs = new chan<boolean>.read[5];
    ups[0] = up0.read;
    ups[1] = up1.read;
    ups[2] = up2.read;
    ups[3] = up3.read;
    ups[4] = up4.read;
    downs[0] = down0.read;
    downs[1] = down1.read;
    downs[2] = down2.read;
    downs[3] = down3.read;
    downs[4] = down4.read;

    par {
	    //securePhilosopher(i, left[i].write, right[i].write, down[i].write, up[i].write)
        securePhilosopher(0, left0.write, right0.write, down0.write, up0.write);
	    securePhilosopher(1, left1.write, right1.write, down1.write, up1.write);
        securePhilosopher(2, left2.write, right2.write, down2.write, up2.write);
        securePhilosopher(3, left3.write, right3.write, down3.write, up3.write);
        securePhilosopher(4, left4.write, right4.write, down4.write, up4.write);

	    // fork(left[i].read, right[(i+1)%max].read);
        Fork(0, left0.read, right1.read);
        Fork(1, left1.read, right2.read);
        Fork(2, left2.read, right3.read);
        Fork(3, left3.read, right4.read);
        Fork(4, left4.read, right0.read);

	    security(ups, downs);
    }
}

public void main(string args[]) {
  //college();
  secureCollege(); 
}