kronecker_delta.c (1229B)
1 /** 2 * @license Apache-2.0 3 * 4 * Copyright (c) 2018 The Stdlib Authors. 5 * 6 * Licensed under the Apache License, Version 2.0 (the "License"); 7 * you may not use this file except in compliance with the License. 8 * You may obtain a copy of the License at 9 * 10 * http://www.apache.org/licenses/LICENSE-2.0 11 * 12 * Unless required by applicable law or agreed to in writing, software 13 * distributed under the License is distributed on an "AS IS" BASIS, 14 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 15 * See the License for the specific language governing permissions and 16 * limitations under the License. 17 */ 18 19 #include "stdlib/math/base/special/kronecker_delta.h" 20 #include "stdlib/math/base/assert/is_nan.h" 21 22 /** 23 * Evaluates the Kronecker delta. 24 * 25 * @param i input value 26 * @param j input value 27 * @return function value 28 * 29 * @example 30 * double v = stdlib_base_kronecker_delta( 3.0, 3.0 ); 31 * // returns 1.0 32 * 33 * @example 34 * double v = stdlib_base_kronecker_delta( 3.0, 3.14 ); 35 * // returns 0.0 36 */ 37 double stdlib_base_kronecker_delta( const double i, const double j ) { 38 if ( stdlib_base_is_nan( i ) || stdlib_base_is_nan( j ) ) { 39 return 0.0 / 0.0; // NaN 40 } 41 if ( i == j ) { 42 return 1.0; 43 } 44 return 0.0; 45 }