main.js (1454B)
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 * Wraps an index on the interval `[0,max]`. 25 * 26 * @param {integer} idx - index 27 * @param {NonNegativeInteger} max - maximum index 28 * @returns {NonNegativeInteger} index 29 * 30 * @example 31 * var idx = wrapIndex( -1, 10 ); 32 * // returns 10 33 * 34 * idx = wrapIndex( 13, 10 ); 35 * // returns 2 36 * 37 * idx = wrapIndex( 6, 10 ); 38 * // returns 6 39 */ 40 function wrapIndex( idx, max ) { 41 var mp1 = max + 1; 42 if ( idx < 0 ) { 43 idx += mp1; // slight optimization to avoid modulo arithmetic when |idx| <= max+1 44 if ( idx < 0 ) { 45 idx %= mp1; 46 if ( idx !== 0 ) { 47 idx += mp1; 48 } 49 } 50 return idx; 51 } 52 if ( idx > max ) { 53 idx -= mp1; // slight optimization to avoid modulo arithmetic when max+1 < idx <= 2*(max+1) 54 if ( idx > max ) { 55 idx %= mp1; 56 } 57 return idx; 58 } 59 return idx; 60 } 61 62 63 // EXPORTS // 64 65 module.exports = wrapIndex;