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* @license Apache-2.0
*
* Copyright (c) 2020 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 isNonnegativeInteger = require( '@stdlib/math/base/assert/is-nonnegative-integer' );
var FLOAT64_MAX_SAFE_NTH_TRIBONACCI = require( '@stdlib/constants/float64/max-safe-nth-tribonacci' ); // eslint-disable-line id-length
var TRIBONACCI = require( './tribonacci.json' );
// MAIN //
/**
* Computes the nth Tribonacci number.
*
* @param {NonNegativeInteger} n - the Tribonacci number to compute
* @returns {NonNegativeInteger} Tribonacci number
*
* @example
* var y = tribonacci( 0 );
* // returns 0
*
* @example
* var y = tribonacci( 1 );
* // returns 0
*
* @example
* var y = tribonacci( 2 );
* // returns 1
*
* @example
* var y = tribonacci( 3 );
* // returns 1
*
* @example
* var y = tribonacci( 4 );
* // returns 2
*
* @example
* var y = tribonacci( 5 );
* // returns 4
*
* @example
* var y = tribonacci( 6 );
* // returns 7
*
* @example
* var y = tribonacci( NaN );
* // returns NaN
*
* @example
* var y = tribonacci( 3.14 );
* // returns NaN
*
* @example
* var y = tribonacci( -1.0 );
* // returns NaN
*/
function tribonacci( n ) {
if (
isnan( n ) ||
!isNonnegativeInteger( n ) ||
n > FLOAT64_MAX_SAFE_NTH_TRIBONACCI
) {
return NaN;
}
return TRIBONACCI[ n ];
}
// EXPORTS //
module.exports = tribonacci;
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