org.tensorics.core.math.Operations.java Source code

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Here is the source code for org.tensorics.core.math.Operations.java

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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.math;

import java.io.Serializable;
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 <T> BinaryOperation<T> inverseBinaryFor(Group<T> group) {
        return new InverseOperationView<>(group);
    }

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

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

    private static final class InverseOperationView<T> implements BinaryOperation<T>, Serializable {
        private static final long serialVersionUID = 1L;

        private final Group<T> group;

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

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

        @Override
        public int hashCode() {
            final int prime = 31;
            int result = 1;
            result = prime * result + ((group == null) ? 0 : group.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;
            }
            InverseOperationView<?> other = (InverseOperationView<?>) obj;
            if (group == null) {
                if (other.group != null) {
                    return false;
                }
            } else if (!group.equals(other.group)) {
                return false;
            }
            return true;
        }

        @Override
        public String toString() {
            return "InverseOperationView [group=" + group + "]";
        }

    }

}