com.thesett.aima.search.util.Searches Maven / Gradle / Ivy

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Search code developed from 'Artificial Intelligence a Modern Approach', Prentice Hall.
There is a newer version: 0.9.97
/*
 * Copyright The Sett Ltd, 2005 to 2014.
 *
 * 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.
 */
package com.thesett.aima.search.util;

import java.util.ArrayList;
import java.util.Collection;
import java.util.HashSet;
import java.util.Iterator;
import java.util.Set;

import com.thesett.aima.search.QueueBasedSearchMethod;
import com.thesett.aima.search.SearchMethod;
import com.thesett.aima.search.SearchNode;
import com.thesett.aima.search.SearchNotExhaustiveException;
import com.thesett.aima.search.Traversable;
import com.thesett.common.util.SequenceIterator;

/**
 * Searches provides static helper methods to simplify common operations using search methods.
 *
 * 
 * CRC Card Responsibilities  Collaborations
 * 
 Provide iterator over all solutions to a search space.  {@link QueueBasedSearchMethod}
 * 
 *
 * @author Rupert Smith
 */
public class Searches
{
    /**
     * Provides an iterator over a search method, that returns successive search solutions on demand.
     *
     * @param      The traversable state type of the search.
     * @param  method The search method to iterate over.
     *
     * @return An iterator over all solution states to the search.
     */
    public static  Iterator allSolutions(SearchMethod method)
    {
        //return new Filterator, T>(allSolutionNodes(method), new ExtractSearchNode());

        // Take a final reference to the search method to use from within the inner class.
        final SearchMethod search = method;

        return new SequenceIterator()
            {
                /**
                 * Generates the next element in the search.
                 *
                 * @return The next solution from the search if one is available, or null if the search is
                 *         complete.
                 */
                public T nextInSequence()
                {
                    try
                    {
                        return search.search();
                    }
                    catch (SearchNotExhaustiveException e)
                    {
                        // SearchNotExhaustiveException means that the search has completed within its designed parameters
                        // without exhausting the search space. Consequently there are no more solutions to find,
                        // the exception can be ignored and the sequence correctly terminated.
                        e = null;

                        return null;
                    }
                }
            };
    }

    /**
     * Finds the set of all goals of a search.
     *
     * @param      The traversable state type of the search.
     * @param  method The search method to find all goals of.
     *
     * @return A set of all goals found.
     */
    public static  Set setOf(SearchMethod method)
    {
        Set result = new HashSet();
        findAll(result, method);

        return result;
    }

    /**
     * Finds a bag of all goals of a search.
     *
     * @param      The traversable state type of the search.
     * @param  method The search method to find all goals of.
     *
     * @return A bag of all goals found.
     */
    public static  Collection bagOf(SearchMethod method)
    {
        Collection result = new ArrayList();
        findAll(result, method);

        return result;
    }

    /**
     * Provides an iterator over a search method, that returns successive search solutions on demand.
     *
     * @param      The operator type of the search.
     * @param      The traversable state type of the search.
     * @param  method The search method to iterate over.
     *
     * @return An iterator over all solutions to the search.
     */
    public static > Iterator> allSolutionPaths(
        QueueBasedSearchMethod method)
    {
        // Take a final reference to the search method to use from within the inner class.
        final QueueBasedSearchMethod search = method;

        return new SequenceIterator>()
            {
                /**
                 * Generates the next element in the search.
                 *
                 * @return The next solution from the search if one is available, or null if the search is
                 *         complete.
                 */
                public SearchNode nextInSequence()
                {
                    try
                    {
                        return search.findGoalPath();
                    }
                    catch (SearchNotExhaustiveException e)
                    {
                        // SearchNotExhaustiveException means that the search has completed within its designed parameters
                        // without exhausting the search space. Consequently there are no more solutions to find,
                        // the exception can be ignored and the sequence correctly terminated.
                        e = null;

                        return null;
                    }
                }
            };
    }

    /**
     * Finals all solutions to a search and inserts them into the specified collection.
     *
     * @param     The traversable state type of the search.
     * @param result The collection to build up the results in.
     * @param method The search to run.
     */
    private static  void findAll(Collection result, SearchMethod method)
    {
        for (Iterator i = allSolutions(method); i.hasNext();)
        {
            T nextSoltn = i.next();

            result.add(nextSoltn);
        }
    }
}