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46 lines
1.6 KiB
Rust
46 lines
1.6 KiB
Rust
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// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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// zip!(a1,a2,a3,a4) is equivalent to:
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// a1.zip(a2).zip(a3).zip(a4).map(|(((x1,x2),x3),x4)| (x1,x2,x3,x4))
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macro_rules! zip {
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// Entry point
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([$a:expr, $b:expr, $($rest:expr),*]) => {
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zip!([$($rest),*], $a.zip($b), (x,y), [x,y])
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};
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// Intermediate steps to build the zipped expression, the match pattern, and
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// and the output tuple of the closure, using macro hygene to repeatedly
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// introduce new variables named 'x'.
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([$a:expr, $($rest:expr),*], $zip:expr, $pat:pat, [$($flat:expr),*]) => {
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zip!([$($rest),*], $zip.zip($a), ($pat,x), [$($flat),*, x])
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};
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// Final step
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([], $zip:expr, $pat:pat, [$($flat:expr),+]) => {
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$zip.map(|$pat| ($($flat),+))
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};
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// Comma
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([$a:expr], $zip:expr, $pat:pat, [$($flat:expr),*]) => {
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zip!([$a,], $zip, $pat, [$($flat),*])
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};
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}
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fn main() {
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let p1 = vec![1i32, 2].into_iter();
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let p2 = vec!["10", "20"].into_iter();
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let p3 = vec![100u16, 200].into_iter();
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let p4 = vec![1000i64, 2000].into_iter();
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let e = zip!([p1,p2,p3,p4]).collect::<Vec<_>>();
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assert_eq!(e[0], (1i32,"10",100u16,1000i64));
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}
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