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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  package org.apache.commons.math4.legacy.analysis;
19  
20  import java.util.function.DoubleBinaryOperator;
21  
22  /**
23   * An interface representing a bivariate real function.
24   *
25   * @since 2.1
26   */
27  @FunctionalInterface
28  public interface BivariateFunction extends DoubleBinaryOperator {
29      /**
30       * Compute the value for the function.
31       *
32       * @param x Abscissa for which the function value should be computed.
33       * @param y Ordinate for which the function value should be computed.
34       * @return the value.
35       */
36      double value(double x, double y);
37  
38      /** {@inheritDoc} */
39      @Override
40      default double applyAsDouble(double x, double y) {
41          return value(x, y);
42      }
43  }