signum.c (1106B)
1 /** 2 * @license Apache-2.0 3 * 4 * Copyright (c) 2020 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/signum.h" 20 #include "stdlib/math/base/assert/is_nan.h" 21 #include <math.h> 22 23 /** 24 * Evaluates the signum function for a double-precision floating-point number. 25 * 26 * @param x number 27 * @return function value 28 * 29 * @example 30 * double y = stdlib_base_signum( -9.0 ); 31 * // returns -1.0 32 */ 33 double stdlib_base_signum( const double x ) { 34 if ( x == 0.0 || stdlib_base_is_nan( x ) ) { 35 return x; // addresses both +-0 36 } 37 return ( x < 0.0 ) ? -1.0 : 1.0; 38 }