63 lines
1.5 KiB
JavaScript
63 lines
1.5 KiB
JavaScript
/**
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* @license Apache-2.0
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*
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* Copyright (c) 2020 The Stdlib Authors.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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'use strict';
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// MODULES //
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var isInteger = require( './../../is-integer' ).isObject;
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var sqrt = require( '@stdlib/math/base/special/sqrt' );
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var floor = require( '@stdlib/math/base/special/floor' );
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// MAIN //
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/**
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* Tests if a value is a number object having a value which is a triangular number.
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*
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* ## Notes
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*
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* - Return values are not reliable for numbers greater than `1125899906842624`.
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*
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* @param {*} value - value to test
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* @returns {boolean} boolean indicating if a value is a number object having a value which is a triangular number
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*
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* @example
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* var bool = isTriangularNumber( 36.0 );
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* // returns false
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*
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* @example
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* var bool = isTriangularNumber( new Number( 36.0 ) );
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* // returns true
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*/
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function isTriangularNumber( value ) {
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var n;
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var x;
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if ( !isInteger( value ) ) {
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return false;
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}
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x = ( 8.0*value.valueOf() ) + 1.0;
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n = floor( sqrt( x ) + 0.5 );
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return n*n === x;
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}
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// EXPORTS //
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module.exports = isTriangularNumber;
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