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ModularArithmetic.js
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56 lines (48 loc) · 1.63 KB
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import { extendedEuclideanGCD } from './ExtendedEuclideanGCD'
/**
* https://brilliant.org/wiki/modular-arithmetic/
* @param {Number} arg1 first argument
* @param {Number} arg2 second argument
* @returns {Number}
*/
export class ModRing {
constructor(MOD) {
this.MOD = MOD
}
isInputValid = (arg1, arg2) => {
if (!this.MOD) {
throw new Error('Modulus must be initialized in the object constructor')
}
if (typeof arg1 !== 'number' || typeof arg2 !== 'number') {
throw new TypeError('Input must be Numbers')
}
}
/**
* Modulus is Distributive property,
* As a result, we separate it into numbers in order to keep it within MOD's range
*/
add = (arg1, arg2) => {
this.isInputValid(arg1, arg2)
return ((arg1 % this.MOD) + (arg2 % this.MOD)) % this.MOD
}
subtract = (arg1, arg2) => {
this.isInputValid(arg1, arg2)
// An extra MOD is added to check negative results
return ((arg1 % this.MOD) - (arg2 % this.MOD) + this.MOD) % this.MOD
}
multiply = (arg1, arg2) => {
this.isInputValid(arg1, arg2)
return ((arg1 % this.MOD) * (arg2 % this.MOD)) % this.MOD
}
/**
*
* It is not Possible to find Division directly like the above methods,
* So we have to use the Extended Euclidean Theorem for finding Multiplicative Inverse
* https://github.com/TheAlgorithms/JavaScript/blob/master/Maths/ExtendedEuclideanGCD.js
*/
divide = (arg1, arg2) => {
// 1st Index contains the required result
// The theorem may have return Negative value, we need to add MOD to make it Positive
return (extendedEuclideanGCD(arg1, arg2)[1] + this.MOD) % this.MOD
}
}