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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  
18  /*
19   * This is not the original file distributed by the Apache Software Foundation
20   * It has been modified by the Hipparchus project
21   */
22  
23  package org.hipparchus.migration.ode;
24  
25  import org.hipparchus.ode.SecondOrderODE;
26  
27  /** This interface represents a second order differential equations set.
28  
29   * <p>This interface should be implemented by all real second order
30   * differential equation problems before they can be handled by the
31   * {@link org.hipparchus.ode.FirstOrderConverter converter to first order}.</p>
32   *
33   * <p>A second order differential equations problem, as seen by an
34   * integrator is the second time derivative <code>d2Y/dt^2</code> of a
35   * state vector <code>Y</code>, both being one dimensional
36   * arrays. From the integrator point of view, this derivative depends
37   * only on the current time <code>t</code>, on the state vector
38   * <code>Y</code> and on the first time derivative of the state
39   * vector.</p>
40   *
41   * <p>For real problems, the derivative depends also on parameters
42   * that do not belong to the state vector (dynamical model constants
43   * for example). These constants are completely outside of the scope
44   * of this interface, the classes that implement it are allowed to
45   * handle them as they want.</p>
46   * @deprecated as of 1.0, replaced with {@link SecondOrderODE}
47   */
48  @Deprecated
49  public interface SecondOrderDifferentialEquations extends SecondOrderODE {
50  
51      /** {@inheritDoc} */
52      @Override
53      default double[] computeSecondDerivatives(double t, double[] y, double[] yDot) {
54          final double[] yDDot = new double[y.length];
55          computeSecondDerivatives(t, y, yDot, yDDot);
56          return yDDot;
57      }
58  
59      /** Get the current time derivative of the state vector.
60       * @param t current value of the independent <I>time</I> variable
61       * @param y array containing the current value of the state vector
62       * @param yDot array containing the current value of the first derivative
63       * of the state vector
64       * @param yDDot placeholder array where to put the second time derivative
65       * of the state vector
66       */
67      void computeSecondDerivatives(double t, double[] y, double[] yDot, double[] yDDot);
68  
69  }