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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
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 *
 * 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.
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// @formatter:on

package org.tensorics.core.math;

import java.util.Collection;
import java.util.List;
import java.util.Map.Entry;

import org.tensorics.core.commons.util.ValuePair;
import org.tensorics.core.math.operations.BinaryOperation;
import org.tensorics.core.math.structures.grouplike.Group;

import com.google.common.collect.ImmutableList;
import com.google.common.collect.ImmutableListMultimap;
import com.google.common.collect.ListMultimap;
import com.google.common.collect.Multimap;

/**
 * Contains utility methods for operations.
 * 
 * @author kfuchsbe
 */
public final class Operations {

    private Operations() {
        /* Only static methods */
    }

    public static  BinaryOperation inverseBinaryFor(Group group) {
        return new InverseOperationView(group);
    }

    public static  List performOnAll(Iterable> valuePairs, BinaryOperation operation) {
        ImmutableList.Builder builder = ImmutableList.builder();
        for (ValuePair valuePair : valuePairs) {
            builder.add(operation.perform(valuePair.left(), valuePair.right()));
        }
        return builder.build();
    }

    public static  ListMultimap mapAll(Multimap> valuePairs, BinaryOperation operation) {
        ImmutableListMultimap.Builder builder = ImmutableListMultimap.builder();
        for (Entry>> entry : valuePairs.asMap().entrySet()) {
            builder.putAll(entry.getKey(), performOnAll(entry.getValue(), operation));
        }
        return builder.build();
    }

    private static final class InverseOperationView implements BinaryOperation {
        private final Group group;

        InverseOperationView(Group group) {
            super();
            this.group = group;
        }

        @Override
        public T perform(T left, T right) {
            return group.operation().perform(left, group.inversion().perform(right));
        }

    }

}