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The DSI utilities are a mish mash of classes accumulated during the last ten years in projects developed at the DSI (Dipartimento di Scienze dell'Informazione, i.e., Information Sciences Department), now DI (Dipartimento di Informatica, i.e., Informatics Department), of the Universita` degli Studi di Milano.

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package it.unimi.dsi.util;

/*		 
 * DSI utilities
 *
 * Copyright (C) 2003-2016 Paolo Boldi and Sebastiano Vigna 
 *
 *  This library is free software; you can redistribute it and/or modify it
 *  under the terms of the GNU Lesser General Public License as published by the Free
 *  Software Foundation; either version 3 of the License, or (at your option)
 *  any later version.
 *
 *  This library is distributed in the hope that it will be useful, but
 *  WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
 *  or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public License
 *  for more details.
 *
 *  You should have received a copy of the GNU Lesser General Public License
 *  along with this program; if not, see .
 *
 */      

import java.util.Comparator;

                                                                                                                                                             
/** A class providing static methods and objects that do useful things with intervals. 
 * 
 * @see Interval
 */

public class Intervals {

	private Intervals() {}

	public final static Interval[] EMPTY_ARRAY = {};

	/** An empty (singleton) interval. */
	public final static Interval EMPTY_INTERVAL = new Interval( 1, 0 );

	/** A singleton located at −∞. */
	public final static Interval MINUS_INFINITY = new Interval( Integer.MIN_VALUE, Integer.MIN_VALUE );

	/** A comparator between intervals defined as follows: 
	 * [a..b] is less than [a'..b'] iff
	 * the first interval starts before or prolongs the second one, that is,  
	 * iff a < a' or a=a' and b' < b.
	 */
	public final static Comparator STARTS_BEFORE_OR_PROLONGS = new Comparator() {
		public int compare( final Interval i1, final Interval i2 ) {
			final int t = i1.left - i2.left;
			if ( t != 0 ) return t;
			return i2.right - i1.right;
		}
	};

	/** A comparator between intervals defined as follows: 
	 * [a..b] is less than [a'..b'] iff
	 * the first interval ends before or is a suffix of the second one, that is,  
	 * iff b < b' or b=b' and a' < a.
	 */
	public final static Comparator ENDS_BEFORE_OR_IS_SUFFIX = new Comparator() {
		public int compare( final Interval i1, final Interval i2 ) {
			final int t = i1.right - i2.right;
			if ( t != 0 ) return t;
			return i2.left - i1.left;
		}
	};

	/** A comparator between intervals defined as follows:
	 * [a..b] is less than [a'..b']
	 * iff the first interval starts after the second one, that is, 
	 * iff a' < a.
	 */
	public final static Comparator STARTS_AFTER = new Comparator() {
		public int compare( final Interval i1, final Interval i2 ) {
			return i2.left - i1.left;
		}
	};                                                                                                                    

	/** A comparator between intervals defined as follows:
	 * [a..b] is less than [a'..b']
	 * iff the first interval starts before the second one, that is, 
	 * iff a < a'.
	 */
	public final static Comparator STARTS_BEFORE = new Comparator() {
		public int compare( final Interval i1, final Interval i2 ) {
			return i1.left - i2.left;
		}
	};                                                                                                                    

	/** A comparator between intervals defined as follows:
	 * [a..b] is less than [a'..b']
	 * iff the first interval ends after the second one, that is, 
	 * iff b' < b.
	 */
	public final static Comparator ENDS_AFTER = new Comparator() {
		public int compare( final Interval i1, final Interval i2 ) {
			return i2.right - i1.right;
		}
	};                                                                                                                    

	/** A comparator between intervals defined as follows:
	 * [a..b] is less than [a'..b']
	 * iff the first interval ends before the second one, that is, 
	 * iff b < b'.
	 */
	public final static Comparator ENDS_BEFORE = new Comparator() {
		public int compare( final Interval i1, final Interval i2 ) {
			return i1.right - i2.right;
		}
	};                                                                                                                    

	/** A comparator between intervals based on their length. */
	public final static Comparator LENGTH_COMPARATOR = new Comparator() {
		public int compare( final Interval i1, final Interval i2 ) {
			return i1.length() - i2.length();
		}
	};                                                                                                                    
}