Data commit

Task/Anonymous-recursion/Rust/anonymous-recursion.rust

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+fn fib(n: i64) -> Option<i64> {
+    // A function declared inside another function does not pollute the outer namespace.
+    fn actual_fib(n: i64) -> i64 {
+        if n < 2 {
+            n
+        } else {
+            actual_fib(n - 1) + actual_fib(n - 2)
+        }
+    }
+
+    if n < 0 {
+        None
+    } else {
+        Some(actual_fib(n))
+    }
+}
+
+fn main() {
+    println!("Fib(-1) = {:?}", fib(-1));
+    println!("Fib(0) = {:?}", fib(0));
+    println!("Fib(1) = {:?}", fib(1));
+    println!("Fib(2) = {:?}", fib(2));
+    println!("Fib(3) = {:?}", fib(3));
+    println!("Fib(4) = {:?}", fib(4));
+    println!("Fib(5) = {:?}", fib(5));
+    println!("Fib(10) = {:?}", fib(10));
+}
+
+#[test]
+fn test_fib() {
+    assert_eq!(fib(0).unwrap(), 0);
+    assert_eq!(fib(1).unwrap(), 1);
+    assert_eq!(fib(2).unwrap(), 1);
+    assert_eq!(fib(3).unwrap(), 2);
+    assert_eq!(fib(4).unwrap(), 3);
+    assert_eq!(fib(5).unwrap(), 5);
+    assert_eq!(fib(10).unwrap(), 55);
+}
+
+#[test]
+fn test_invalid_argument() {
+    assert_eq!(fib(-1), None);
+}