85 lines
2.0 KiB
JavaScript
85 lines
2.0 KiB
JavaScript
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/**
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* @license Apache-2.0
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*
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* Copyright (c) 2018 The Stdlib Authors.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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'use strict';
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// MODULES //
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var isPositiveInteger = require( '@stdlib/assert/is-positive-integer' ).isPrimitive;
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var incrmsum = require( './../../../incr/msum' );
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// MAIN //
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/**
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* Returns an accumulator function which incrementally computes a moving sum of products.
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*
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* @param {PositiveInteger} W - window size
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* @throws {TypeError} must provide a positive integer
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* @returns {Function} accumulator function
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*
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* @example
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* var accumulator = incrmsumprod( 3 );
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*
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* var sum = accumulator();
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* // returns null
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*
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* sum = accumulator( 2.0, 3.0 );
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* // returns 6.0
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*
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* sum = accumulator( -5.0, 2.0 );
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* // returns -4.0
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*
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* sum = accumulator( 3.0, -2.0 );
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* // returns -10.0
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*
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* sum = accumulator( 5.0, 3.0 );
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* // returns -1.0
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*
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* sum = accumulator();
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* // returns -1.0
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*/
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function incrmsumprod( W ) {
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var sum;
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if ( !isPositiveInteger( W ) ) {
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throw new TypeError( 'invalid argument. Must provide a positive integer. Value: `' + W + '`.' );
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}
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sum = incrmsum( W );
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return accumulator;
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/**
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* If provided a value, the accumulator function returns an updated sum. If not provided a value, the accumulator function returns the current sum.
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*
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* @private
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* @param {number} [x] - input value
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* @param {number} [y] - input value
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* @returns {(number|null)} sum or null
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*/
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function accumulator( x, y ) {
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if ( arguments.length === 0 ) {
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return sum();
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}
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return sum( x*y );
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}
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}
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// EXPORTS //
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module.exports = incrmsumprod;
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