xlogy.js (1522B)
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 'use strict'; 20 21 // MODULES // 22 23 var isnan = require( './../../../../base/assert/is-nan' ); 24 var ln = require( './../../../../base/special/ln' ); 25 26 27 // MAIN // 28 29 /** 30 * Computes `x * ln(y)` so that the result is `0` if `x = 0`. 31 * 32 * @param {number} x - input value 33 * @param {number} y - input value 34 * @returns {number} function value 35 * 36 * @example 37 * var out = xlogy( 3.0, 2.0 ); 38 * // returns ~2.079 39 * 40 * @example 41 * var out = xlogy( 1.5, 5.9 ); 42 * // returns ~2.662 43 * 44 * @example 45 * var out = xlogy( 0.9, 1.0 ); 46 * // returns 0.0 47 * 48 * @example 49 * var out = xlogy( 0.0, -2.0 ); 50 * // returns 0.0 51 * 52 * @example 53 * var out = xlogy( 1.5, NaN ); 54 * // returns NaN 55 * 56 * @example 57 * var out = xlogy( 0.0, NaN ); 58 * // returns NaN 59 * 60 * @example 61 * var out = xlogy( NaN, 2.3 ); 62 * // returns NaN 63 */ 64 function xlogy( x, y ) { 65 if ( x === 0.0 && !isnan( y ) ) { 66 return 0.0; 67 } 68 return x * ln( y ); 69 } 70 71 72 // EXPORTS // 73 74 module.exports = xlogy;