/*

Returns the sum of a geometric progression

Article on Geometric Progression: https://en.wikipedia.org/wiki/Geometric_series

Examples:

> sumOfGeometricProgression(2, 0.5, 6)

3.9375

> sumOfGeometricProgression(0.5, 10, 3)

55.5

> sumOfGeometricProgression(0.5, 10, Infinity)

Error: The geometric progression is diverging, and its sum cannot be calculated

*/

/**

*

* @param {Number} firstTerm The first term of the geometric progression

* @param {Number} commonRatio The common ratio of the geometric progression

* @param {Number} numOfTerms The number of terms in the progression

*/

function sumOfGeometricProgression(firstTerm, commonRatio, numOfTerms) {

if (!Number.isFinite(numOfTerms)) {

/*

If the number of Terms is Infinity, the common ratio needs to be less than 1 to be a convergent geometric progression

Article on Convergent Series: https://en.wikipedia.org/wiki/Convergent_series

*/

if (Math.abs(commonRatio) < 1) return firstTerm / (1 - commonRatio)

throw new Error(

'The geometric progression is diverging, and its sum cannot be calculated'

)

}

if (commonRatio === 1) return firstTerm * numOfTerms

return (

(firstTerm * (Math.pow(commonRatio, numOfTerms) - 1)) / (commonRatio - 1)

)

}

export { sumOfGeometricProgression }