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Returns undefined if not invertible

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Barry Brown 2024-06-13 20:57:17 +00:00
parent 8530c47cb8
commit bc559888e6
1 changed files with 4 additions and 3 deletions
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7
src/core/Utils.mjs
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@ -1265,13 +1265,14 @@ class Utils {
/** /**
* Finds the modular inverse of two values. * Calculates the modular multiplicative inverse of a (mod n).
* Uses the Extended Euclidean Algorithm. * Uses the Extended Euclidean Algorithm.
* https://en.wikipedia.org/wiki/Extended_Euclidean_algorithm
* *
* @author Barry B [profbbrown@gmail.com] * @author Barry B [profbbrown@gmail.com]
* @param {number} a * @param {number} a
* @param {number} n * @param {number} n
* @returns {number|null} * @returns {number|undefined} The inverse of a (mod n), or undefined
*/ */
static modInv(a, n) { static modInv(a, n) {
let t = 0, newT = 1, r = n, newR = a; let t = 0, newT = 1, r = n, newR = a;
@ -1282,7 +1283,7 @@ class Utils {
[r, newR] = [newR, r - q * newR]; [r, newR] = [newR, r - q * newR];
} }
if (r > 1) return null; if (r > 1) return undefined;
if (t < 0) t = t + n; if (t < 0) t = t + n;
return t; return t;