feat(maths): added IsPrime (TheAlgorithms#102)

* feat(maths): added IsPrime

* Fix `IsPrime` for perfect squares

* Add perfect square to the tests

---------

Co-authored-by: Lars Müller <[email protected]>

Author: T1LT

maths/is_prime.ts

@@ -0,0 +1,28 @@
+/**
+ * @function IsPrime
+ * @description Determine if given number is prime.
+ * @param {number} num - A natural number.
+ * @return {boolean} - Whether the given number is prime.
+ * @see https://en.wikipedia.org/wiki/Prime_number
+ * @example IsPrime(2) = false
+ * @example IsPrime(3) = true
+ */
+
+export const IsPrime = (num: number): boolean => {
+  // raise corresponding errors upon invalid inputs
+  if (num <= 0 || !Number.isInteger(num)) {
+    throw new Error("only natural numbers are supported");
+  }
+
+  // handle input being 1
+  if (num === 1) return false;
+
+  // iterate from 2 to the square root of num to find a factor
+  // return false upon finding a factor
+  for (let i = 2; i <= Math.sqrt(num); i++) {
+    if (num % i === 0) return false;
+  }
+
+  // if the entire loop runs without finding a factor, return true
+  return true;
+};

maths/test/is_prime.test.ts

@@ -0,0 +1,19 @@
+import { IsPrime } from "../is_prime";
+
+describe("IsPrime", () => {
+  test.each([[1, false], [2, true], [3, true], [3*3, false], [13, true], [24, false]])(
+    "correct output for %i",
+    (nums, expected) => {
+      expect(IsPrime(nums)).toBe(expected);
+    },
+  );
+
+  test.each([-890, -5.56, -7, 0.73, 4.2, NaN, -Infinity, Infinity])(
+    "should throw an error for non natural number %d",
+    (num) => {
+      expect(() => IsPrime(num)).toThrowError(
+        "only natural numbers are supported",
+      );
+    },
+  );
+});