| // run-pass |
| // zip!(a1,a2,a3,a4) is equivalent to: |
| // a1.zip(a2).zip(a3).zip(a4).map(|(((x1,x2),x3),x4)| (x1,x2,x3,x4)) |
| macro_rules! zip { |
| // Entry point |
| ([$a:expr, $b:expr, $($rest:expr),*]) => { |
| zip!([$($rest),*], $a.zip($b), (x,y), [x,y]) |
| }; |
| |
| // Intermediate steps to build the zipped expression, the match pattern, and |
| // and the output tuple of the closure, using macro hygiene to repeatedly |
| // introduce new variables named 'x'. |
| ([$a:expr, $($rest:expr),*], $zip:expr, $pat:pat, [$($flat:expr),*]) => { |
| zip!([$($rest),*], $zip.zip($a), ($pat,x), [$($flat),*, x]) |
| }; |
| |
| // Final step |
| ([], $zip:expr, $pat:pat, [$($flat:expr),+]) => { |
| $zip.map(|$pat| ($($flat),+)) |
| }; |
| |
| // Comma |
| ([$a:expr], $zip:expr, $pat:pat, [$($flat:expr),*]) => { |
| zip!([$a,], $zip, $pat, [$($flat),*]) |
| }; |
| } |
| |
| fn main() { |
| let p1 = vec![1i32, 2].into_iter(); |
| let p2 = vec!["10", "20"].into_iter(); |
| let p3 = vec![100u16, 200].into_iter(); |
| let p4 = vec![1000i64, 2000].into_iter(); |
| |
| let e = zip!([p1,p2,p3,p4]).collect::<Vec<_>>(); |
| assert_eq!(e[0], (1i32,"10",100u16,1000i64)); |
| } |
