1   /* Copyright 2002-2019 CS Systèmes d'Information
2    * Licensed to CS Systèmes d'Information (CS) under one or more
3    * contributor license agreements.  See the NOTICE file distributed with
4    * this work for additional information regarding copyright ownership.
5    * CS 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.orekit.utils;
18  
19  import org.orekit.propagation.SpacecraftState;
20  
21  /** Interface representing a vector function depending on {@link SpacecraftState}.
22   * @see Differentiation#differentiate(StateFunction, int, org.orekit.attitudes.AttitudeProvider,
23   * org.orekit.orbits.OrbitType, org.orekit.orbits.PositionAngle, double, int)
24   * @see StateJacobian
25   * @author Luc Maisonobe
26   * @since 8.0
27   */
28  public interface StateFunction {
29  
30      /** Evaluate the function.
31       * @param state spacecraft state as the sole free parameter of the function.
32       * @return vector value of the function
33       */
34      double[] value(SpacecraftState state);
35  
36  }