feat: add is_prime

ladderz/src/pre_algebra/unit1.rs

@@ -136,6 +136,38 @@ pub fn get_multiples_in_range(n: u32, end: u32) -> HashSet<u32> {
     multiples
 }
 
+/// Checks if a positive integer `n` is a prime number.
+///
+/// A prime number is a positive integer greater than 1 that cannot
+/// be evenly divisible by any positive integers other than 1 and itself.
+///
+/// # Examples
+///
+/// ```rust
+/// use ladderz::pre_algebra::is_prime;
+///
+/// assert!(!is_prime(1)); // 1 is not a prime number
+/// assert!(is_prime(2)); // 2 is a prime number
+/// assert!(!is_prime(4)); // 4 is not a prime number
+/// assert!(is_prime(7)); // 7 is a prime number
+/// ```
+///
+/// # Note
+///
+/// This function returns `false` for values of `n` less than 2 because, by definition, prime
+/// numbers must be greater than 1.
+pub fn is_prime(n: u32) -> bool {
+    if n == 1 {
+        return false;
+    };
+    for num in 2..n {
+        if n % num == 0 {
+            return false;
+        }
+    }
+    true
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;

notebooks/pre-algebra/unit1.ipynb

@@ -199,6 +199,41 @@
     "assert get_multiples_in_range(3, 20) == {3, 6, 9, 12, 15, 18}\n",
     "assert get_multiples_in_range(5, 50) == {5, 10, 15, 20, 25, 30, 35, 40, 45, 50}"
    ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "**Write a program that determines whether a positive integer `n` is prime.**\n",
+    "\n",
+    "For example for `n = 7`, the output of `is_prime(7)` may be:\n",
+    "\n",
+    "```\n",
+    "True\n",
+    "```"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 13,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "def is_prime(n: int) -> bool:\n",
+    "    if n == 1: return False\n",
+    "    for num in range(2, n):\n",
+    "        if n % num == 0:\n",
+    "            return False\n",
+    "    return True\n",
+    "\n",
+    "assert is_prime(1) == False\n",
+    "assert is_prime(2) == True\n",
+    "assert is_prime(3) == True\n",
+    "assert is_prime(4) == False\n",
+    "assert is_prime(24) == False\n",
+    "assert is_prime(59) == True\n",
+    "assert is_prime(72) == False"
+   ]
   }
  ],
  "metadata": {