main.js (1548B)
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 getHighWord = require( './../../../../float64/base/get-high-word' ); 24 25 26 // MAIN // 27 28 /** 29 * Returns a boolean indicating if the sign bit is on (true) or off (false). 30 * 31 * @param {number} x - input value 32 * @returns {boolean} boolean indicating if sign bit is on or off 33 * 34 * @example 35 * var bool = signbit( 4.0 ); 36 * // returns false 37 * 38 * @example 39 * var bool = signbit( -9.14e-307 ); 40 * // returns true 41 * 42 * @example 43 * var bool = signbit( 0.0 ); 44 * // returns false 45 * 46 * @example 47 * var bool = signbit( -0.0 ); 48 * // returns true 49 */ 50 function signbit( x ) { 51 // Extract from the input value a higher order word (unsigned 32-bit integer) containing the exponent and sign: 52 var high = getHighWord( x ); 53 54 // Shift off all bits which are not the sign bit and check if the sign bit is on: 55 return ( high >>> 31 ) ? true : false; // eslint-disable-line no-unneeded-ternary 56 } 57 58 59 // EXPORTS // 60 61 module.exports = signbit;