foo.cpp

/* let mut v = vec![1, 2, 3];

for i in &v {
    println!("{}", i);
    v.push(34); // sorry, no can do
} */

let mutable v = vector{ 1, 2, 3 };

v ->> λi {
  print(i);
  // v.push(34); // sorry, no can do
  async v.push(34); // okay, but only after this mapping actually ends
};