atanh.js (1482B)
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 isinfinite = require( './../../../../../base/assert/is-infinite' ); 24 var isnan = require( './../../../../../base/assert/is-nan' ); 25 var ln = require( './../../../../../base/special/ln' ); 26 27 28 // MAIN // 29 30 /** 31 * Computes the hyperbolic arctangent of a number. 32 * 33 * @param {number} x - input value 34 * @returns {number} hyperbolic arctangent (in radians) 35 * 36 * @example 37 * var v = atanh( 0.0 ); 38 * // returns 0.0 39 * 40 * @example 41 * var v = atanh( 0.9 ); 42 * // returns ~1.472 43 * 44 * @example 45 * var v = atanh( 1.0 ); 46 * // returns Infinity 47 * 48 * @example 49 * v = atanh( -1.0 ); 50 * // returns -Infinity 51 * 52 * @example 53 * var v = atanh( NaN ); 54 * // returns NaN 55 */ 56 function atanh( x ) { 57 if ( x === 0.0 ) { 58 return x; 59 } 60 if ( 61 isnan( x ) || 62 isinfinite( x ) 63 ) { 64 return NaN; 65 } 66 return 0.5 * ln( (1.0+x) / (1.0-x) ); 67 } 68 69 70 // EXPORTS // 71 72 module.exports = atanh;