1#![no_std] 2 3#[macro_export] 4macro_rules! chain { 5 [] => (::core::iter::empty()); 6 [$x0:expr $(, $x:expr)*] => ($x0.into_iter().chain(chain![$($x),*])); 7 [$x0:expr $(, $x:expr)* ,] => (chain!($x0 $(, $x)*)); 8}