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• PrefixMap.java

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src.it.unimi.dsi.util.PrefixMap Maven / Gradle / Ivy

/*
 * DSI utilities
 *
 * Copyright (C) 2004-2020 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 .
 *
 */

package it.unimi.dsi.util;

import it.unimi.dsi.fastutil.objects.Object2ObjectFunction;

/** A map from prefixes to string intervals (and possibly vice versa).
 *
 * 
Instances of this class provide the services of a {@link StringMap}, but by assuming
 * the strings are lexicographically ordered, they can provide further information by
 * exposing a {@linkplain #rangeMap() function from string prefixes to intervals} and a
 * {@linkplain #prefixMap() function from intervals to string prefixes}.
 *
 * 
In the first case, given a prefix, we can ask for the range of strings starting
 * with that prefix, expressed as an {@link Interval}. This information is very useful to
 * satisfy prefix queries (e.g., monitor*) with a brute-force approach.
 *
 * 
Optionally, a prefix map may provide the opposite service: given an interval of terms, it
 *  may provide the maximum common prefix. This feature can be checked for by calling
 *  {@link #prefixMap()}.
 *
 * @author Sebastiano Vigna
 * @since 0.9.2
 */

public interface PrefixMap extends StringMap {
	/** Returns a function mapping prefixes to ranges of strings.
	 *
	 * @return a function mapping prefixes to ranges of strings.
	 */
	Object2ObjectFunction rangeMap();

	/** Returns a function mapping ranges of strings to common prefixes (optional operation).
	 *
	 * @return a function mapping ranges of strings to common prefixes, or {@code null} if this
	 * map does not support prefixes.
	 */
	Object2ObjectFunction prefixMap();
}