factory.js (1675B)
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 evalpoly = require( './../../../../base/tools/evalpoly' ).factory; 24 var pow = require( './../../../../base/special/pow' ); 25 var abs = require( './../../../../base/special/abs' ); 26 var coefficients = require( './coefficients.js' ); 27 28 29 // MAIN // 30 31 /** 32 * Returns a function for evaluating a Lucas polynomial. 33 * 34 * @param {integer} n - Lucas polynomial to evaluate 35 * @returns {Function} function for evaluating a Lucas polynomial 36 * 37 * @example 38 * var polyval = factory( 5 ); 39 * 40 * var v = polyval( 1.0 ); 41 * // returns 11.0 42 * 43 * v = polyval( 2.0 ); 44 * // returns 82.0 45 */ 46 function factory( n ) { 47 var coefs; 48 var an; 49 var f; 50 var s; 51 52 an = abs( n ); 53 coefs = coefficients( an ); 54 55 f = evalpoly( coefs ); 56 s = pow( -1.0, an ); 57 if ( n >= 0 || s === 1.0 ) { 58 return f; 59 } 60 return polyval; 61 62 /** 63 * Evaluates a Lucas polynomial. 64 * 65 * @private 66 * @param {number} x - value at which to evaluate a Lucas polynomial 67 * @returns {number} result 68 */ 69 function polyval( x ) { 70 return -1.0 * f( x ); 71 } 72 } 73 74 75 // EXPORTS // 76 77 module.exports = factory;