trunc2.js (1557B)
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 isInfinite = require( './../../../../base/assert/is-infinite' ); 25 var pow = require( './../../../../base/special/pow' ); 26 var floor = require( './../../../../base/special/floor' ); 27 var log2 = require( './../../../../base/special/log2' ); 28 29 30 // MAIN // 31 32 /** 33 * Rounds a numeric value to the nearest power of two toward zero. 34 * 35 * @param {number} x - input value 36 * @returns {number} rounded value 37 * 38 * @example 39 * var v = trunc2( 3.141592653589793 ); 40 * // returns 2.0 41 * 42 * @example 43 * var v = trunc2( 13.0 ); 44 * // returns 8.0 45 * 46 * @example 47 * var v = trunc2( -0.314 ); 48 * // returns -0.25 49 */ 50 function trunc2( x ) { 51 var sign; 52 if ( 53 isnan( x ) || 54 isInfinite( x ) || 55 x === 0.0 56 ) { 57 return x; 58 } 59 if ( x < 0 ) { 60 x = -x; 61 sign = -1.0; 62 } else { 63 sign = 1.0; 64 } 65 return sign * pow( 2.0, floor( log2( x ) ) ); 66 } 67 68 69 // EXPORTS // 70 71 module.exports = trunc2;