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Tensorics is a java framework which uses a tensor as a central object. A tensor represents a set of values placed in an N-dimensional space. Wherever you are tempted to use maps of maps, a tensor might be a good choice ;-) Tensorics provides methods to create, transform and performing calculations with those tensors.

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// @formatter:off
/*******************************************************************************
*
* This file is part of tensorics.
* 
* Copyright (c) 2008-2011, CERN. All rights reserved.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
*     http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
* 
******************************************************************************/
// @formatter:on

package org.tensorics.core.tensor;

import static org.tensorics.core.tensor.Coordinates.requireValidCoordinates;

import java.io.Serializable;
import java.util.Collections;
import java.util.HashSet;
import java.util.Set;

import com.google.common.base.Preconditions;
import com.google.common.collect.ClassToInstanceMap;
import com.google.common.collect.ImmutableMultiset;
import com.google.common.collect.Interner;
import com.google.common.collect.Interners;

/**
 * Defines the position of a value within a tensor in the N-dimensional
 * coordinate space.
 * 
 * @author agorzaws
 */
public final class Position implements Serializable {

	private static final long serialVersionUID = 1L;

	private static final Interner INTERNER = Interners.newWeakInterner();

	/*
	 * NOTE: This has to be after the cachedPositions initialization, because
	 * the 'of' method uses it!
	 */
	private static final Position EMPTY_POSITION = Position.createFrom(Collections.emptySet());

	@SuppressWarnings("PMD.AvoidFieldNameMatchingMethodName")
	private final ClassToInstanceMap coordinates;

	private Position(Set coordinates) {
		this.coordinates = Coordinates.mapOf(coordinates);
		if (this.coordinates.containsKey(Position.class)) {
			throw new IllegalArgumentException("A position is contained in the collection of coordinates."
					+ "This is most-probably a programming mistake and therefore not allowed.");
		}
	}

	@SuppressWarnings("PMD.ShortMethodName")
	public static Position of(Set coordinates) {
		return createFrom(requireValidCoordinates(coordinates));
	}

	private static Position createFrom(Set coordinates) {
		return INTERNER.intern(new Position(coordinates));
	}

	public static Position empty() {
		return EMPTY_POSITION;
	}

	@SafeVarargs
	@SuppressWarnings("PMD.ShortMethodName")
	public static Position of(Object... coordinates) {
		return createFrom(requireValidCoordinates(ImmutableMultiset.copyOf(coordinates)));
	}

	public ClassToInstanceMap getCoordinates() {
		return coordinates;
	}

	public  CS coordinateFor(Class dimension) {
		return getCoordinates().getInstance(dimension);
	}

	public Set coordinates() {
		return new HashSet<>(coordinates.values());
	}

	/**
	 * Retrieves the dimensions of this position (i.e. the type of the
	 * containing coordinates)
	 * 
	 * @return the types of the coordinates
	 */
	public Set> dimensionSet() {
		return getCoordinates().keySet();
	}

	/**
	 * Checks if the position is consistent with the given dimensions.
	 * Conformity means that the position contains exactly one coordinate for
	 * each dimension in the given set of dimensions (classes of coordinates).
	 * 
	 * @param dimensions
	 *            the dimensions for which conformity has to be checked.
	 * @return {@code true} if the position is conform, {@code false} if not.
	 */
	public boolean isConsistentWith(Set> dimensions) {
		Preconditions.checkArgument(dimensions != null, "Argument '" + "dimensions" + "' must not be null!");
		return dimensions.equals(dimensionSet());
	}

	@Override
	public int hashCode() {
		final int prime = 31;
		int result = 1;
		result = prime * result + ((coordinates == null) ? 0 : coordinates.hashCode());
		return result;
	}

	@Override
	public boolean equals(Object obj) {
		if (this == obj) {
			return true;
		}
		if (obj == null) {
			return false;
		}
		if (getClass() != obj.getClass()) {
			return false;
		}
		Position other = (Position) obj;
		if (coordinates == null) {
			if (other.coordinates != null) {
				return false;
			}
		} else if (!coordinates.equals(other.coordinates)) {
			return false;
		}
		return true;
	}

	@Override
	public String toString() {
		return coordinates.values().toString();
	}

} 















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