main.js (2057B)
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 isPositiveInteger = require( '@stdlib/assert/is-positive-integer' ).isPrimitive; 24 var incrmsum = require( './../../../incr/msum' ); 25 26 27 // MAIN // 28 29 /** 30 * Returns an accumulator function which incrementally computes a moving sum of products. 31 * 32 * @param {PositiveInteger} W - window size 33 * @throws {TypeError} must provide a positive integer 34 * @returns {Function} accumulator function 35 * 36 * @example 37 * var accumulator = incrmsumprod( 3 ); 38 * 39 * var sum = accumulator(); 40 * // returns null 41 * 42 * sum = accumulator( 2.0, 3.0 ); 43 * // returns 6.0 44 * 45 * sum = accumulator( -5.0, 2.0 ); 46 * // returns -4.0 47 * 48 * sum = accumulator( 3.0, -2.0 ); 49 * // returns -10.0 50 * 51 * sum = accumulator( 5.0, 3.0 ); 52 * // returns -1.0 53 * 54 * sum = accumulator(); 55 * // returns -1.0 56 */ 57 function incrmsumprod( W ) { 58 var sum; 59 if ( !isPositiveInteger( W ) ) { 60 throw new TypeError( 'invalid argument. Must provide a positive integer. Value: `' + W + '`.' ); 61 } 62 sum = incrmsum( W ); 63 return accumulator; 64 65 /** 66 * If provided a value, the accumulator function returns an updated sum. If not provided a value, the accumulator function returns the current sum. 67 * 68 * @private 69 * @param {number} [x] - input value 70 * @param {number} [y] - input value 71 * @returns {(number|null)} sum or null 72 */ 73 function accumulator( x, y ) { 74 if ( arguments.length === 0 ) { 75 return sum(); 76 } 77 return sum( x*y ); 78 } 79 } 80 81 82 // EXPORTS // 83 84 module.exports = incrmsumprod;