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/*
 * Copyright (c) 2010-2021 Haifeng Li. All rights reserved.
 *
 * Smile is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * Smile 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with Smile.  If not, see .
 */

package smile.math.distance;

/**
 * A metric function defines a distance between elements of a set. Besides
 * non-negativity, isolation, and symmetry, it also has to satisfy triangular
 * inequality.
 * 
 *  non-negativity: {@code d(x, y) >= 0}
 * 
 isolation: {@code d(x, y) = 0} if and only if {@code x = y}
 * 
 symmetry: {@code d(x, y) = d(x, y)}
 * 
 triangular inequality: {@code |x - y| + |y - z| >= |x - z|}.
 * 
 *
 * @param  the input type of metric function.
 *
 * @author Haifeng Li
 */
public interface Metric extends Distance {

}