1 /* 2 * Licensed to the Apache Software Foundation (ASF) under one or more 3 * contributor license agreements. See the NOTICE file distributed with 4 * this work for additional information regarding copyright ownership. 5 * The ASF licenses this file to You under the Apache License, Version 2.0 6 * (the "License"); you may not use this file except in compliance with 7 * the License. You may obtain a copy of the License at 8 * 9 * http://www.apache.org/licenses/LICENSE-2.0 10 * 11 * Unless required by applicable law or agreed to in writing, software 12 * distributed under the License is distributed on an "AS IS" BASIS, 13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 14 * See the License for the specific language governing permissions and 15 * limitations under the License. 16 */ 17 package org.apache.commons.geometry.core; 18 19 import java.util.Collection; 20 import java.util.List; 21 import java.util.stream.Collectors; 22 23 /** This interface defines mappings between a space and one of its subspaces. 24 25 * <p>Subspaces are the lower-dimension subsets of a space. For example, 26 * in an n-dimension space, the subspaces are the (n-1) dimension space, 27 * the (n-2) dimension space, and so on. This interface can be used regardless 28 * of the difference in number of dimensions between the space and the target 29 * subspace. For example, a line in 3D Euclidean space can use this interface 30 * to map directly from 3D Euclidean space to 1D Euclidean space (ie, the location 31 * along the line).</p> 32 * 33 * @param <P> Point type defining the embedding space. 34 * @param <S> Point type defining the embedded subspace. 35 */ 36 public interface Embedding<P extends Point<P>, S extends Point<S>> { 37 38 /** Transform a space point into a subspace point. 39 * @param pt n-dimension point of the space 40 * @return lower-dimension point of the subspace corresponding to 41 * the specified space point 42 * @see #toSpace 43 */ 44 S toSubspace(P pt); 45 46 /** Transform a collection of space points into subspace points. 47 * @param pts collection of n-dimension points to transform 48 * @return collection of transformed lower-dimension points. 49 * @see #toSubspace(Point) 50 */ 51 default List<S> toSubspace(final Collection<P> pts) { 52 return pts.stream().map(this::toSubspace).collect(Collectors.toList()); 53 } 54 55 /** Transform a subspace point into a space point. 56 * @param pt lower-dimension point of the subspace 57 * @return n-dimension point of the space corresponding to the 58 * specified subspace point 59 * @see #toSubspace(Point) 60 */ 61 P toSpace(S pt); 62 63 /** Transform a collection of subspace points into space points. 64 * @param pts collection of lower-dimension points to transform 65 * @return collection of transformed n-dimension points. 66 * @see #toSpace(Point) 67 */ 68 default List<P> toSpace(final Collection<S> pts) { 69 return pts.stream().map(this::toSpace).collect(Collectors.toList()); 70 } 71 }