1 /// Converts an iterator of tuples into a tuple of containers.
2 ///
3 /// `unzip()` consumes an entire iterator of n-ary tuples, producing `n` collections, one for each
4 /// column.
5 ///
6 /// This function is, in some sense, the opposite of [`multizip`].
7 ///
8 /// ```
9 /// use itertools::multiunzip;
10 ///
11 /// let inputs = vec![(1, 2, 3), (4, 5, 6), (7, 8, 9)];
12 ///
13 /// let (a, b, c): (Vec<_>, Vec<_>, Vec<_>) = multiunzip(inputs);
14 ///
15 /// assert_eq!(a, vec![1, 4, 7]);
16 /// assert_eq!(b, vec![2, 5, 8]);
17 /// assert_eq!(c, vec![3, 6, 9]);
18 /// ```
19 ///
20 /// [`multizip`]: crate::multizip
multiunzip<FromI, I>(i: I) -> FromI where I: IntoIterator, I::IntoIter: MultiUnzip<FromI>,21 pub fn multiunzip<FromI, I>(i: I) -> FromI
22 where
23 I: IntoIterator,
24 I::IntoIter: MultiUnzip<FromI>,
25 {
26 i.into_iter().multiunzip()
27 }
28
29 /// An iterator that can be unzipped into multiple collections.
30 ///
31 /// See [`.multiunzip()`](crate::Itertools::multiunzip) for more information.
32 pub trait MultiUnzip<FromI>: Iterator {
33 /// Unzip this iterator into multiple collections.
multiunzip(self) -> FromI34 fn multiunzip(self) -> FromI;
35 }
36
37 macro_rules! impl_unzip_iter {
38 ($($T:ident => $FromT:ident),*) => (
39 #[allow(non_snake_case)]
40 impl<IT: Iterator<Item = ($($T,)*)>, $($T, $FromT: Default + Extend<$T>),* > MultiUnzip<($($FromT,)*)> for IT {
41 fn multiunzip(self) -> ($($FromT,)*) {
42 // This implementation mirrors the logic of Iterator::unzip resp. Extend for (A, B) as close as possible.
43 // Unfortunately a lot of the used api there is still unstable (https://github.com/rust-lang/rust/issues/72631).
44 //
45 // Iterator::unzip: https://doc.rust-lang.org/src/core/iter/traits/iterator.rs.html#2825-2865
46 // Extend for (A, B): https://doc.rust-lang.org/src/core/iter/traits/collect.rs.html#370-411
47
48 let mut res = ($($FromT::default(),)*);
49 let ($($FromT,)*) = &mut res;
50
51 // Still unstable #72631
52 // let (lower_bound, _) = self.size_hint();
53 // if lower_bound > 0 {
54 // $($FromT.extend_reserve(lower_bound);)*
55 // }
56
57 self.fold((), |(), ($($T,)*)| {
58 // Still unstable #72631
59 // $( $FromT.extend_one($T); )*
60 $( $FromT.extend(std::iter::once($T)); )*
61 });
62 res
63 }
64 }
65 );
66 }
67
68 impl_unzip_iter!();
69 impl_unzip_iter!(A => FromA);
70 impl_unzip_iter!(A => FromA, B => FromB);
71 impl_unzip_iter!(A => FromA, B => FromB, C => FromC);
72 impl_unzip_iter!(A => FromA, B => FromB, C => FromC, D => FromD);
73 impl_unzip_iter!(A => FromA, B => FromB, C => FromC, D => FromD, E => FromE);
74 impl_unzip_iter!(A => FromA, B => FromB, C => FromC, D => FromD, E => FromE, F => FromF);
75 impl_unzip_iter!(A => FromA, B => FromB, C => FromC, D => FromD, E => FromE, F => FromF, G => FromG);
76 impl_unzip_iter!(A => FromA, B => FromB, C => FromC, D => FromD, E => FromE, F => FromF, G => FromG, H => FromH);
77 impl_unzip_iter!(A => FromA, B => FromB, C => FromC, D => FromD, E => FromE, F => FromF, G => FromG, H => FromH, I => FromI);
78 impl_unzip_iter!(A => FromA, B => FromB, C => FromC, D => FromD, E => FromE, F => FromF, G => FromG, H => FromH, I => FromI, J => FromJ);
79 impl_unzip_iter!(A => FromA, B => FromB, C => FromC, D => FromD, E => FromE, F => FromF, G => FromG, H => FromH, I => FromI, J => FromJ, K => FromK);
80 impl_unzip_iter!(A => FromA, B => FromB, C => FromC, D => FromD, E => FromE, F => FromF, G => FromG, H => FromH, I => FromI, J => FromJ, K => FromK, L => FromL);
81