/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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 org.apache.commons.math3.geometry.spherical.oned;
import org.apache.commons.math3.geometry.Point;
import org.apache.commons.math3.geometry.Space;
import org.apache.commons.math3.geometry.euclidean.twod.Vector2D;
import org.apache.commons.math3.util.FastMath;
import org.apache.commons.math3.util.MathUtils;
/** This class represents a point on the 1-sphere.
* <p>Instances of this class are guaranteed to be immutable.</p>
* @since 3.3
*/
public class S1Point implements Point<Sphere1D> {
// CHECKSTYLE: stop ConstantName
/** A vector with all coordinates set to NaN. */
public static final S1Point NaN = new S1Point(Double.NaN, Vector2D.NaN);
// CHECKSTYLE: resume ConstantName
/** Serializable UID. */
private static final long serialVersionUID = 20131218L;
/** Azimuthal angle \( \alpha \). */
private final double alpha;
/** Corresponding 2D normalized vector. */
private final Vector2D vector;
/** Simple constructor.
* Build a vector from its coordinates
* @param alpha azimuthal angle \( \alpha \)
* @see #getAlpha()
*/
public S1Point(final double alpha) {
this(MathUtils.normalizeAngle(alpha, FastMath.PI),
new Vector2D(FastMath.cos(alpha), FastMath.sin(alpha)));
}
/** Build a point from its internal components.
* @param alpha azimuthal angle \( \alpha \)
* @param vector corresponding vector
*/
private S1Point(final double alpha, final Vector2D vector) {
this.alpha = alpha;
this.vector = vector;
}
/** Get the azimuthal angle \( \alpha \).
* @return azimuthal angle \( \alpha \)
* @see #S1Point(double)
*/
public double getAlpha() {
return alpha;
}
/** Get the corresponding normalized vector in the 2D euclidean space.
* @return normalized vector
*/
public Vector2D getVector() {
return vector;
}
/** {@inheritDoc} */
public Space getSpace() {
return Sphere1D.getInstance();
}
/** {@inheritDoc} */
public boolean isNaN() {
return Double.isNaN(alpha);
}
/** {@inheritDoc} */
public double distance(final Point<Sphere1D> point) {
return distance(this, (S1Point) point);
}
/** Compute the distance (angular separation) between two points.
* @param p1 first vector
* @param p2 second vector
* @return the angular separation between p1 and p2
*/
public static double distance(S1Point p1, S1Point p2) {
return Vector2D.angle(p1.vector, p2.vector);
}
/**
* Test for the equality of two points on the 2-sphere.
* <p>
* If all coordinates of two points are exactly the same, and none are
* <code>Double.NaN</code>, the two points are considered to be equal.
* </p>
* <p>
* <code>NaN</code> coordinates are considered to affect globally the vector
* and be equals to each other - i.e, if either (or all) coordinates of the
* 2D vector are equal to <code>Double.NaN</code>, the 2D vector is equal to
* {@link #NaN}.
* </p>
*
* @param other Object to test for equality to this
* @return true if two points on the 2-sphere objects are equal, false if
* object is null, not an instance of S2Point, or
* not equal to this S2Point instance
*
*/
@Override
public boolean equals(Object other) {
if (this == other) {
return true;
}
if (other instanceof S1Point) {
final S1Point rhs = (S1Point) other;
if (rhs.isNaN()) {
return this.isNaN();
}
return alpha == rhs.alpha;
}
return false;
}
/**
* Get a hashCode for the 2D vector.
* <p>
* All NaN values have the same hash code.</p>
*
* @return a hash code value for this object
*/
@Override
public int hashCode() {
if (isNaN()) {
return 542;
}
return 1759 * MathUtils.hash(alpha);
}
}