All files main.js

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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.
*/
 
'use strict';
 
// MODULES //
 
var isnan = require( '@stdlib/math/base/assert/is-nan' );
var isint = require( '@stdlib/math/base/assert/is-integer' );
 
 
// MAIN //
 
/**
* Evaluates a normalized Hermite polynomial using double-precision floating-point arithmetic.
*
* @param {NonNegativeInteger} n - nonnegative polynomial degree
* @param {number} x - evaluation point
* @returns {number} function value
*
* @example
* var v = normhermitepoly( 1, 0.5 );
* // returns 0.5
*
* @example
* var v = normhermitepoly( 0, 0.5 );
* // returns 1.0
*
* @example
* var v = normhermitepoly( 2, 0.5 );
* // returns -0.75
*
* @example
* var v = normhermitepoly( -1, 0.5 );
* // returns NaN
*/
function normhermitepoly( n, x ) {
	var y1;
	var y2;
	var y3;
	var i;
 
	if ( isnan( n ) || isnan( x ) || n < 0 || !isint( n ) ) {
		return NaN;
	}
	if ( n === 0 ) {
		// `x` is completely canceled from the expression:
		return 1.0;
	}
	if ( n === 1 ) {
		return x;
	}
	y2 = 1.0;
	y3 = 0.0;
	for ( i = n; i > 1; i-- ) {
		y1 = (x*y2) - (i*y3);
		y3 = y2;
		y2 = y1;
	}
	return (x*y2) - y3;
}
 
 
// EXPORTS //
 
module.exports = normhermitepoly;