/* PROBLEM:

   A trip is a series of legs. Each leg has two attributes:
     -- the distance traveled 
     -- the time needed
*/

// -----------------------------------------------------------------------------
// represent a series of legs 
interface ITrip {
  // convert relative distances in legs to absolute distances 
  ITrip relativeToAbs();
  // accumulator: soFar measures the distance between the 
  // start of the trip and __this__ trip
  ITrip relativeToAbsAccu(int soFar);
}

class Mt implements ITrip {
  Mt() {
  }
  
  ITrip relativeToAbs() {
    return new Mt();
  }
  
  ITrip relativeToAbsAccu(int soFar) {
    return new Mt();
  }
}

class ConsLeg implements ITrip {
  Leg first; 
  ITrip rest; 
  ConsLeg(Leg first, ITrip rest) {
    this. first = first; 
    this. rest = rest; 
  }
  
  ITrip relativeToAbs() {
    return this.relativeToAbsAccu(0);
  }

  ITrip relativeToAbsAccu(int soFar) {
    return 
      new ConsLeg(this.first.rTA(soFar), 
                  this.rest.relativeToAbsAccu(soFar+this.first.distance));
  }
}

// -----------------------------------------------------------------------------
// one leg of a salesman's trip 
class Leg {
  int time; // in minutes 
  int distance; // in miles 
  Leg(int time, int distance) {
    this. time = time; 
    this. distance = distance; 
  }
  
  // convert the leg's distance from relative to absolute, 
  // assuming soFar is the distance traveled from beginning of trip
  Leg rTA(int soFar) {
    return new Leg(this.time,this.distance+soFar);
  }
  
  // to compute the speed at which the salesman travelled __this__ leg 
  double speed() {
    return (1.0 * this.distance) / this.time;
  }
}


// -----------------------------------------------------------------------------
// examples of legs and trips 
class Examples {
  Leg l1 = new Leg(-10,-20); 
  Leg l2 = new Leg(100,200);
  Leg l3 = new Leg(100,500);
  Leg l4 = new Leg(200,10);
  boolean test1 = check l2.speed() expect 2.0 within .0001;
  boolean test2 = check l3.speed() expect 5.0 within .01;
  boolean test3 = check l4.speed() expect .05 within .01;

  boolean testX = check l4.rTA(200) expect new Leg(200,210);
  
  ITrip trip1 = new Mt();
  ITrip trip2 = new ConsLeg(l2,trip1);
  ITrip trip3 = new ConsLeg(l3,trip2); 
  
  boolean test4 = check trip1.relativeToAbs() expect trip1; 
  boolean test5 = check trip2.relativeToAbs() expect trip2; 
  boolean test6 = check trip3.relativeToAbs() expect 
  new ConsLeg(l3,new ConsLeg(new Leg(100,700),trip1));
}