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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_64_0/boost/math/special_functions/gamma.hpp}. The implementation has been modified for JavaScript.
*
* ```text
* Copyright John Maddock 2006-7, 2013-14.
* Copyright Paul A. Bristow 2007, 2013-14.
* Copyright Nikhar Agrawal 2013-14.
* Copyright Christopher Kormanyos 2013-14.
*
* 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';
// TODO: consider moving this to a separate pkg: @stdlib/math/base/special/xsinpi
// MODULES //
var isOdd = require( './../../../../../base/assert/is-odd' );
var floor = require( './../../../../../base/special/floor' );
var sinpi = require( './../../../../../base/special/sinpi' );
// MAIN //
/**
* Calculates `x * sin(pi * x)`, taking extra care near when `x` is near a whole number.
*
* @private
* @param {number} x - input value
* @returns {number} function value
*/
function sinpx( x ) {
var result;
var dist;
var sign;
var fl;
sign = 1;
if ( x < 0.0 ) {
x = -x;
}
fl = floor( x );
if ( isOdd(fl) ) {
fl += 1;
dist = fl - x;
sign = -sign;
} else {
dist = x - fl;
}
if ( dist > 0.5 ) {
dist = 1.0 - dist;
}
result = sinpi( dist );
return sign*x*result;
}
// EXPORTS //
module.exports = sinpx;
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