#![allow(unreachable_code)]


fn main() {
    println!("{:?}", {
        use std::mem::replace; pub fn fibonacci() -> impl Iterator<Item=u128> { let (mut a, mut b) = (0, 1); std::iter::from_fn(|| replace(&mut a, replace(&mut b, a + b))) }
    });
}


/* ~~~~=== stderr ===~~~~
   Compiling playground v0.0.1 (/playground)
error[E0425]: cannot find function `from_fn` in module `std::iter`
 --> src/main.rs:6:121
  |
6 |         use std::mem::replace; pub fn fibonacci() -> impl Iterator<Item=u128> { let (mut a, mut b) = (0, 1); std::iter::from_fn(|| replace(&mut a, replace(&mut b, a + b))) }
  |                                                                                                                         ^^^^^^^ not found in `std::iter`

error: aborting due to previous error

For more information about this error, try `rustc --explain E0425`.
error: Could not compile `playground`.

To learn more, run the command again with --verbose.

*/

/* ~~~~=== stdout ===~~~~

*/