order.js (1642B)
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 // FUNCTIONS // 22 23 /** 24 * Returns a comparison result. If `-1`, `a` comes before `b`. If `1`, `b` comes before `a`. If `0`, the order stays the same. 25 * 26 * @private 27 * @param {number} a - first number 28 * @param {number} b - second number 29 * @returns {boolean} comparison result 30 */ 31 function compareFunction( a, b ) { 32 if ( a < b ) { 33 return -1; 34 } 35 if ( a > b ) { 36 return 1; 37 } 38 return 0; 39 } 40 41 42 // MAIN // 43 44 /** 45 * Returns a permutation which rearranges input array. 46 * 47 * @private 48 * @param {ArrayLike} x - input array-like object 49 * @returns {Array} permutation array 50 */ 51 function order( x ) { 52 var arr; 53 var i; 54 55 arr = new Array( x.length ); 56 for ( i = 0; i < x.length; i++ ) { 57 arr[ i ] = i; 58 } 59 return arr.sort( compare ); 60 61 /** 62 * Compare the elements of the input array. 63 * 64 * @private 65 * @param {number} a - first number 66 * @param {number} b - second number 67 * @returns {boolean} comparison result 68 */ 69 function compare( a, b ) { 70 return compareFunction( x[a], x[b] ); 71 } 72 } 73 74 75 // EXPORTS // 76 77 module.exports = order;