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/**
* @license Apache-2.0
*
* Copyright (c) 2018 The Stdlib Authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
*
* ## Notice
*
* The original C++ code and copyright notice are from the [Boost library]{@link http://www.boost.org/doc/libs/1_37_0/boost/math/special_functions/gamma.hpp}. The implementation has been modified for JavaScript.
*
* ```text
* (C) Copyright John Maddock 2006.
* (C) Copyright Paul A. Bristow 2007.
*
* Use, modification and distribution are subject to the
* Boost Software License, Version 1.0. (See accompanying file
* LICENSE or copy at http://www.boost.org/LICENSE_1_0.txt)
* ```
*/
'use strict';
/**
* Series representation for upper fraction when `z` is small.
*
* @private
* @param {number} a - function parameter
* @param {number} x - function parameter
* @returns {Function} series function
*/
function smallGamma2Series( a, x ) {
var result;
var apn;
var n;
var r;
result = -x;
x = -x;
apn = a + 1.0;
n = 1;
return next;
/**
* Calculate the next term of the series.
*
* @private
* @returns {number} series expansion term
*/
function next() {
r = result / apn;
result *= x;
n += 1;
result /= n;
apn += 1.0;
return r;
}
}
// EXPORTS //
module.exports = smallGamma2Series;
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