add fib.py example with `@bend~ decorator

examples/fib.py

@@ -0,0 +1,49 @@
+from typing import TypeVar
+T = TypeVar("T")
+
+
+def bend(fn: T) -> T:
+    """
+    Decorator to hind compiler that the recursive function should be translated
+    to a inline `bend` block.
+
+    This will be internal to the library.
+    """
+    return fn
+
+
+def fib_recursive(n: int) -> int:
+    """
+    Calculates fibonacci numbers recursively.
+    """
+    match n:
+        case 0:
+            return 0
+        case 1:
+            return 1
+        case _:
+            return fib_recursive(n - 2) + fib_recursive(n - 1)
+
+
+def fib_iterative(n: int) -> int:
+    """
+    Calculates fibonacci numbers iteratively (tail-recursively).
+    """
+
+    @bend
+    def go(a: int, b: int, n: int) -> int:
+        if n == 0:
+            return a
+        else:
+            return go(b, a + b, n - 1)
+
+    return go(0, 1, n)
+
+
+def main():
+    print(fib_iterative(10))
+    print(fib_recursive(10))
+
+
+if __name__ == "__main__":
+    main()