1 <?php
2 
3 /**
4  * Hoa
5  *
6  *
7  * @license
8  *
9  * New BSD License
10  *
11  * Copyright © 2007-2017, Hoa community. All rights reserved.
12  *
13  * Redistribution and use in source and binary forms, with or without
14  * modification, are permitted provided that the following conditions are met:
15  *     * Redistributions of source code must retain the above copyright
16  *       notice, this list of conditions and the following disclaimer.
17  *     * Redistributions in binary form must reproduce the above copyright
18  *       notice, this list of conditions and the following disclaimer in the
19  *       documentation and/or other materials provided with the distribution.
20  *     * Neither the name of the Hoa nor the names of its contributors may be
21  *       used to endorse or promote products derived from this software without
22  *       specific prior written permission.
23  *
24  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
25  * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
26  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
27  * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDERS AND CONTRIBUTORS BE
28  * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
29  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
30  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
31  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
32  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
33  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
34  * POSSIBILITY OF SUCH DAMAGE.
35  */
36 
37 namespace Hoa\Math;
38 
39 /**
40  * Class \Hoa\Math\Util.
41  *
42  * Some Math functions.
43  *
44  * @copyright  Copyright © 2007-2017 Hoa community
45  * @license    New BSD License
46  */
47 class Util
48 {
49     /**
50      * @description 'Kronecker delta: δ_i^j = 1 if i = j, 0 if i ≠ j';
51      * @requires    i: integer() and
52      *              j: integer();
53      * @ensures     \pred('\\result === (int) ($i === $j)');
54      */
55     public static function δ($i, $j)
56     {
57         return (int) ($i === $j);
58     }
59 }
60