log.js (1391B)
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 ln = require( './../../../../base/special/ln' ); 24 25 26 // MAIN // 27 28 /** 29 * Computes the base `b` logarithm of `x`. 30 * 31 * @param {NonNegativeNumber} x - input value 32 * @param {NonNegativeNumber} b - base 33 * @returns {number} logarithm (base `b`) 34 * 35 * @example 36 * var v = log( 100.0, 10.0 ); 37 * // returns 2.0 38 * 39 * @example 40 * var v = log( 16.0, 2.0 ); 41 * // returns 4.0 42 * 43 * @example 44 * var v = log( 5.0, 1.0 ); 45 * // returns Infinity 46 * 47 * @example 48 * var v = log( NaN, 2.0 ); 49 * // returns NaN 50 * 51 * @example 52 * var v = log( 1.0, NaN ); 53 * // returns NaN 54 * 55 * @example 56 * var v = log( -4.0, 2.0 ); 57 * // returns NaN 58 * 59 * @example 60 * var v = log( 4.0, -2.0 ); 61 * // returns NaN 62 */ 63 function log( x, b ) { 64 return ln( x ) / ln( b ); 65 } 66 67 68 // EXPORTS // 69 70 module.exports = log;