Rename sheet folders to assure proper sorting

aufgaben/sheet02/sol1/prime.rs

@@ -0,0 +1,62 @@
+//! Aufgabe 1.2: Primzahltest
+
+fn main() {
+    for i in 1..20 {
+        print!("{}", i);
+        if is_prime(i) {
+            print!("*");
+        }
+        println!("");
+    }
+}
+
+/// Tests if the given number `n` is prime.
+fn is_prime(n: u64) -> bool {
+    // Note: there are nicer *and* faster ways to do a primality test. But that
+    // was not necessarily the point of this task.
+
+    // 1 is special and yes: 1 is not a prime!
+    if n <= 1 {
+        return false;
+    }
+
+    // Iterator through all possible divisors
+    for d in 2..n {
+        if n % d == 0 {
+            return false;
+        }
+    }
+
+    true
+}
+
+#[test]
+fn small_primes() {
+    assert!(is_prime(2));
+    assert!(is_prime(3));
+    assert!(is_prime(5));
+    assert!(is_prime(7));
+}
+
+#[test]
+fn small_composites() {
+    assert!(!is_prime(1));
+    assert!(!is_prime(4));
+    assert!(!is_prime(6));
+    assert!(!is_prime(8));
+    assert!(!is_prime(9));
+}
+
+#[test]
+fn large_primes() {
+    assert!(is_prime(1_300_769));
+    assert!(is_prime(1_300_297));
+    assert!(is_prime(7_367_287));
+}
+
+#[test]
+fn large_composites() {
+    assert!(!is_prime(908_209));
+    assert!(!is_prime(3_073_009));
+    assert!(!is_prime(4_897_369));
+}