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.math3.geometry.spherical.oned;
18 
19 import org.apache.commons.math3.geometry.Point;
20 import org.apache.commons.math3.geometry.Space;
21 import org.apache.commons.math3.geometry.euclidean.twod.Vector2D;
22 import org.apache.commons.math3.util.FastMath;
23 import org.apache.commons.math3.util.MathUtils;
24 
25 /** This class represents a point on the 1-sphere.
26  * <p>Instances of this class are guaranteed to be immutable.</p>
27  * @since 3.3
28  */
29 public class S1Point implements Point<Sphere1D> {
30 
31    // CHECKSTYLE: stop ConstantName
32     /** A vector with all coordinates set to NaN. */
33     public static final S1Point NaN = new S1Point(Double.NaN, Vector2D.NaN);
34     // CHECKSTYLE: resume ConstantName
35 
36     /** Serializable UID. */
37     private static final long serialVersionUID = 20131218L;
38 
39     /** Azimuthal angle \( \alpha \). */
40     private final double alpha;
41 
42     /** Corresponding 2D normalized vector. */
43     private final Vector2D vector;
44 
45     /** Simple constructor.
46      * Build a vector from its coordinates
47      * @param alpha azimuthal angle \( \alpha \)
48      * @see #getAlpha()
49      */
S1Point(final double alpha)50     public S1Point(final double alpha) {
51         this(MathUtils.normalizeAngle(alpha, FastMath.PI),
52              new Vector2D(FastMath.cos(alpha), FastMath.sin(alpha)));
53     }
54 
55     /** Build a point from its internal components.
56      * @param alpha azimuthal angle \( \alpha \)
57      * @param vector corresponding vector
58      */
S1Point(final double alpha, final Vector2D vector)59     private S1Point(final double alpha, final Vector2D vector) {
60         this.alpha  = alpha;
61         this.vector = vector;
62     }
63 
64     /** Get the azimuthal angle \( \alpha \).
65      * @return azimuthal angle \( \alpha \)
66      * @see #S1Point(double)
67      */
getAlpha()68     public double getAlpha() {
69         return alpha;
70     }
71 
72     /** Get the corresponding normalized vector in the 2D euclidean space.
73      * @return normalized vector
74      */
getVector()75     public Vector2D getVector() {
76         return vector;
77     }
78 
79     /** {@inheritDoc} */
getSpace()80     public Space getSpace() {
81         return Sphere1D.getInstance();
82     }
83 
84     /** {@inheritDoc} */
isNaN()85     public boolean isNaN() {
86         return Double.isNaN(alpha);
87     }
88 
89     /** {@inheritDoc} */
distance(final Point<Sphere1D> point)90     public double distance(final Point<Sphere1D> point) {
91         return distance(this, (S1Point) point);
92     }
93 
94     /** Compute the distance (angular separation) between two points.
95      * @param p1 first vector
96      * @param p2 second vector
97      * @return the angular separation between p1 and p2
98      */
distance(S1Point p1, S1Point p2)99     public static double distance(S1Point p1, S1Point p2) {
100         return Vector2D.angle(p1.vector, p2.vector);
101     }
102 
103     /**
104      * Test for the equality of two points on the 2-sphere.
105      * <p>
106      * If all coordinates of two points are exactly the same, and none are
107      * <code>Double.NaN</code>, the two points are considered to be equal.
108      * </p>
109      * <p>
110      * <code>NaN</code> coordinates are considered to affect globally the vector
111      * and be equals to each other - i.e, if either (or all) coordinates of the
112      * 2D vector are equal to <code>Double.NaN</code>, the 2D vector is equal to
113      * {@link #NaN}.
114      * </p>
115      *
116      * @param other Object to test for equality to this
117      * @return true if two points on the 2-sphere objects are equal, false if
118      *         object is null, not an instance of S2Point, or
119      *         not equal to this S2Point instance
120      *
121      */
122     @Override
equals(Object other)123     public boolean equals(Object other) {
124 
125         if (this == other) {
126             return true;
127         }
128 
129         if (other instanceof S1Point) {
130             final S1Point rhs = (S1Point) other;
131             if (rhs.isNaN()) {
132                 return this.isNaN();
133             }
134 
135             return alpha == rhs.alpha;
136         }
137 
138         return false;
139 
140     }
141 
142     /**
143      * Get a hashCode for the 2D vector.
144      * <p>
145      * All NaN values have the same hash code.</p>
146      *
147      * @return a hash code value for this object
148      */
149     @Override
hashCode()150     public int hashCode() {
151         if (isNaN()) {
152             return 542;
153         }
154         return 1759 * MathUtils.hash(alpha);
155     }
156 
157 }
158