001    /*
002     * Licensed to the Apache Software Foundation (ASF) under one or more
003     * contributor license agreements.  See the NOTICE file distributed with
004     * this work for additional information regarding copyright ownership.
005     * The ASF licenses this file to You under the Apache License, Version 2.0
006     * (the "License"); you may not use this file except in compliance with
007     * the License.  You may obtain a copy of the License at
008     *
009     *      http://www.apache.org/licenses/LICENSE-2.0
010     *
011     * Unless required by applicable law or agreed to in writing, software
012     * distributed under the License is distributed on an "AS IS" BASIS,
013     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014     * See the License for the specific language governing permissions and
015     * limitations under the License.
016     */
017    package org.apache.commons.math3.geometry.partitioning;
018    
019    import org.apache.commons.math3.geometry.Space;
020    
021    /** This interface is used to visit {@link BSPTree BSP tree} nodes.
022    
023     * <p>Navigation through {@link BSPTree BSP trees} can be done using
024     * two different point of views:</p>
025     * <ul>
026     *   <li>
027     *     the first one is in a node-oriented way using the {@link
028     *     BSPTree#getPlus}, {@link BSPTree#getMinus} and {@link
029     *     BSPTree#getParent} methods. Terminal nodes without associated
030     *     {@link SubHyperplane sub-hyperplanes} can be visited this way,
031     *     there is no constraint in the visit order, and it is possible
032     *     to visit either all nodes or only a subset of the nodes
033     *   </li>
034     *   <li>
035     *     the second one is in a sub-hyperplane-oriented way using
036     *     classes implementing this interface which obeys the visitor
037     *     design pattern. The visit order is provided by the visitor as
038     *     each node is first encountered. Each node is visited exactly
039     *     once.
040     *   </li>
041     * </ul>
042    
043     * @param <S> Type of the space.
044    
045     * @see BSPTree
046     * @see SubHyperplane
047    
048     * @version $Id: BSPTreeVisitor.java 1416643 2012-12-03 19:37:14Z tn $
049     * @since 3.0
050     */
051    public interface BSPTreeVisitor<S extends Space> {
052    
053        /** Enumerate for visit order with respect to plus sub-tree, minus sub-tree and cut sub-hyperplane. */
054        enum Order {
055            /** Indicator for visit order plus sub-tree, then minus sub-tree,
056             * and last cut sub-hyperplane.
057             */
058            PLUS_MINUS_SUB,
059    
060            /** Indicator for visit order plus sub-tree, then cut sub-hyperplane,
061             * and last minus sub-tree.
062             */
063            PLUS_SUB_MINUS,
064    
065            /** Indicator for visit order minus sub-tree, then plus sub-tree,
066             * and last cut sub-hyperplane.
067             */
068            MINUS_PLUS_SUB,
069    
070            /** Indicator for visit order minus sub-tree, then cut sub-hyperplane,
071             * and last plus sub-tree.
072             */
073            MINUS_SUB_PLUS,
074    
075            /** Indicator for visit order cut sub-hyperplane, then plus sub-tree,
076             * and last minus sub-tree.
077             */
078            SUB_PLUS_MINUS,
079    
080            /** Indicator for visit order cut sub-hyperplane, then minus sub-tree,
081             * and last plus sub-tree.
082             */
083            SUB_MINUS_PLUS;
084        }
085    
086        /** Determine the visit order for this node.
087         * <p>Before attempting to visit an internal node, this method is
088         * called to determine the desired ordering of the visit. It is
089         * guaranteed that this method will be called before {@link
090         * #visitInternalNode visitInternalNode} for a given node, it will be
091         * called exactly once for each internal node.</p>
092         * @param node BSP node guaranteed to have a non null cut sub-hyperplane
093         * @return desired visit order, must be one of
094         * {@link Order#PLUS_MINUS_SUB}, {@link Order#PLUS_SUB_MINUS},
095         * {@link Order#MINUS_PLUS_SUB}, {@link Order#MINUS_SUB_PLUS},
096         * {@link Order#SUB_PLUS_MINUS}, {@link Order#SUB_MINUS_PLUS}
097         */
098        Order visitOrder(BSPTree<S> node);
099    
100        /** Visit a BSP tree node node having a non-null sub-hyperplane.
101         * <p>It is guaranteed that this method will be called after {@link
102         * #visitOrder visitOrder} has been called for a given node,
103         * it wil be called exactly once for each internal node.</p>
104         * @param node BSP node guaranteed to have a non null cut sub-hyperplane
105         * @see #visitLeafNode
106         */
107        void visitInternalNode(BSPTree<S> node);
108    
109        /** Visit a leaf BSP tree node node having a null sub-hyperplane.
110         * @param node leaf BSP node having a null sub-hyperplane
111         * @see #visitInternalNode
112         */
113        void visitLeafNode(BSPTree<S> node);
114    
115    }