1 /*
2 * Licensed to the Hipparchus project 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 Hipparchus project 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 * https://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.hipparchus.special.elliptic.jacobi;
18
19 import org.hipparchus.util.FastMath;
20
21 /** Algorithm for computing the principal Jacobi functions for negative parameter m.
22 * <p>
23 * The rules for negative parameter change are given in Abramowitz and Stegun, section 16.10.
24 * </p>
25 * @since 2.0
26 */
27 class NegativeParameter extends JacobiElliptic {
28
29 /** Algorithm to use for the positive parameter. */
30 private final JacobiElliptic algorithm;
31
32 /** Input scaling factor. */
33 private final double inputScale;
34
35 /** output scaling factor. */
36 private final double outputScale;
37
38 /** Simple constructor.
39 * @param m parameter of the Jacobi elliptic function (must be negative here)
40 */
41 NegativeParameter(final double m) {
42 super(m);
43 final double omM = 1.0 - m;
44 algorithm = JacobiEllipticBuilder.build(-m / omM);
45 inputScale = FastMath.sqrt(omM);
46 outputScale = 1.0 / inputScale;
47 }
48
49 /** {@inheritDoc} */
50 @Override
51 public CopolarN valuesN(final double u) {
52 final CopolarD trioD = new CopolarD(algorithm.valuesN(u * inputScale));
53 return new CopolarN(outputScale * trioD.sd(), trioD.cd(), trioD.nd());
54 }
55
56 }