main.js (1610B)
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 // MAIN // 22 23 /** 24 * Computes an absolute value of a signed 32-bit integer in two's complement format. 25 * 26 * ## Method 27 * 28 * - Assume two's complement format. 29 * - Create a mask by applying a sign propagating right-shift. For negative integers, this results in all `1`'s. For nonnegative integers, this results in all `0`'s. 30 * - XOR the mask with `x`. For negative integers, this is the equivalent of a NOT. For nonnegative integers, this is a no-op. 31 * - Subtract the mask to recover the absolute value. For negative integers, this adds `1`, which is `-x` when using two's complement. For nonnegative integers, this subtracts `0`. 32 * 33 * @param {integer32} x - integer 34 * @returns {integer32} absolute value 35 * 36 * @example 37 * var v = labs( -10|0 ); 38 * // returns 10 39 */ 40 function labs( x ) { 41 var mask; 42 var y; 43 44 y = x|0; // asm type annotation 45 mask = ( y >> 31 )|0; // asm type annotation 46 return ((y ^ mask) - mask)|0; // asm type annotation 47 } 48 49 50 // EXPORTS // 51 52 module.exports = labs;