/**
 * An ordered pair is a pair which is ordered lexicographically.
 *  
 * @author Rossmanith
 *
 * @param <A> The type of the first value.
 * @param <B> The type of the second value.
 */
public class OPair<A extends Comparable<A>,B extends Comparable<B>>
extends Pair<A,B> implements Comparable<OPair<A,B>> {

    /**
     * Create a new pair with first value a and second value b
     * @param a The first value
     * @param b The second value
     */
    public OPair(A a, B b) {
        super(a, b);
    }

    /**
     * Equality is defined pairwise, i.e. [a1,b1] = [a2,b2] iff
     * a1 = a2 and b1 = b2. Note that o must be an ordered pair.
     * @param o The object to compare with this.
     */
    @SuppressWarnings("unchecked")
    @Override
    public boolean equals(Object o) {        
        OPair<A,B> p = (OPair<A,B>) o;
        return a.equals(p.a) && b.equals(p.b);
    }

    /**
     * Compares this pair with another pair p. Here
     * [a1,b1] is smaller/greater than [a2,b2] iff
     * a1 is smaller/greater than a2 or, if a1 = a2 then
     * b1 is smaller/greater than b2
     * @param p t
     * @return a negative number, if this < p, 
     * 0, if this = p, 
     * and a positive number, if this > p (confere the contract of {@link java.lang.Comparable})
     * @see java.lang.Comparable 
     */
    public int compareTo(OPair<A,B> p) {
        if(a.equals(p.a)) return  b.compareTo(p.b);
        else return a.compareTo(p.a);
    }

    @Override
    public int hashCode() {
        return (a.hashCode() << 8 | b.hashCode());
    }

}