factory.js (1855B)
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 constantFunction = require( '@stdlib/utils/constant-function' ); 24 var isnan = require( './../../../../base/assert/is-nan' ); 25 var isint = require( './../../../../base/assert/is-integer' ); 26 var SQRT2 = require( '@stdlib/constants/float64/sqrt-two' ); 27 var pow = require( './../../../../base/special/pow' ); 28 var normhermitepoly = require( './../../../../base/tools/normhermitepoly' ); 29 30 31 // MAIN // 32 33 /** 34 * Returns a function for evaluating a physicist's Hermite polynomial. 35 * 36 * @param {NonNegativeInteger} n - polynomial degree 37 * @returns {Function} function for evaluating a physicist's Hermite polynomial 38 * 39 * @example 40 * var polyval = factory( 2 ); 41 * 42 * var v = polyval( 0.5 ); 43 * // returns -1.0 44 */ 45 function factory( n ) { 46 var c; 47 if ( n < 0 || isnan( n ) || !isint( n ) ) { 48 return constantFunction( NaN ); 49 } 50 if ( n === 0 ) { 51 return constantFunction( 1.0 ); 52 } 53 c = pow( 2.0, 0.5*n ); 54 return polyval; 55 56 /** 57 * Evaluates a physicist's Hermite polynomial. 58 * 59 * @private 60 * @param {number} x - value at which to evaluate a physicist's Hermite polynomial 61 * @returns {number} result 62 */ 63 function polyval( x ) { 64 return c * normhermitepoly( n, SQRT2*x ); 65 } 66 } 67 68 69 // EXPORTS // 70 71 module.exports = factory;