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-rw-r--r--third_party/rust/itertools/src/unziptuple.rs80
1 files changed, 80 insertions, 0 deletions
diff --git a/third_party/rust/itertools/src/unziptuple.rs b/third_party/rust/itertools/src/unziptuple.rs
new file mode 100644
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+++ b/third_party/rust/itertools/src/unziptuple.rs
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+/// Converts an iterator of tuples into a tuple of containers.
+///
+/// `unzip()` consumes an entire iterator of n-ary tuples, producing `n` collections, one for each
+/// column.
+///
+/// This function is, in some sense, the opposite of [`multizip`].
+///
+/// ```
+/// use itertools::multiunzip;
+///
+/// let inputs = vec![(1, 2, 3), (4, 5, 6), (7, 8, 9)];
+///
+/// let (a, b, c): (Vec<_>, Vec<_>, Vec<_>) = multiunzip(inputs);
+///
+/// assert_eq!(a, vec![1, 4, 7]);
+/// assert_eq!(b, vec![2, 5, 8]);
+/// assert_eq!(c, vec![3, 6, 9]);
+/// ```
+///
+/// [`multizip`]: crate::multizip
+pub fn multiunzip<FromI, I>(i: I) -> FromI
+where
+ I: IntoIterator,
+ I::IntoIter: MultiUnzip<FromI>,
+{
+ i.into_iter().multiunzip()
+}
+
+/// An iterator that can be unzipped into multiple collections.
+///
+/// See [`.multiunzip()`](crate::Itertools::multiunzip) for more information.
+pub trait MultiUnzip<FromI>: Iterator {
+ /// Unzip this iterator into multiple collections.
+ fn multiunzip(self) -> FromI;
+}
+
+macro_rules! impl_unzip_iter {
+ ($($T:ident => $FromT:ident),*) => (
+ #[allow(non_snake_case)]
+ impl<IT: Iterator<Item = ($($T,)*)>, $($T, $FromT: Default + Extend<$T>),* > MultiUnzip<($($FromT,)*)> for IT {
+ fn multiunzip(self) -> ($($FromT,)*) {
+ // This implementation mirrors the logic of Iterator::unzip resp. Extend for (A, B) as close as possible.
+ // Unfortunately a lot of the used api there is still unstable (https://github.com/rust-lang/rust/issues/72631).
+ //
+ // Iterator::unzip: https://doc.rust-lang.org/src/core/iter/traits/iterator.rs.html#2825-2865
+ // Extend for (A, B): https://doc.rust-lang.org/src/core/iter/traits/collect.rs.html#370-411
+
+ let mut res = ($($FromT::default(),)*);
+ let ($($FromT,)*) = &mut res;
+
+ // Still unstable #72631
+ // let (lower_bound, _) = self.size_hint();
+ // if lower_bound > 0 {
+ // $($FromT.extend_reserve(lower_bound);)*
+ // }
+
+ self.fold((), |(), ($($T,)*)| {
+ // Still unstable #72631
+ // $( $FromT.extend_one($T); )*
+ $( $FromT.extend(std::iter::once($T)); )*
+ });
+ res
+ }
+ }
+ );
+}
+
+impl_unzip_iter!();
+impl_unzip_iter!(A => FromA);
+impl_unzip_iter!(A => FromA, B => FromB);
+impl_unzip_iter!(A => FromA, B => FromB, C => FromC);
+impl_unzip_iter!(A => FromA, B => FromB, C => FromC, D => FromD);
+impl_unzip_iter!(A => FromA, B => FromB, C => FromC, D => FromD, E => FromE);
+impl_unzip_iter!(A => FromA, B => FromB, C => FromC, D => FromD, E => FromE, F => FromF);
+impl_unzip_iter!(A => FromA, B => FromB, C => FromC, D => FromD, E => FromE, F => FromF, G => FromG);
+impl_unzip_iter!(A => FromA, B => FromB, C => FromC, D => FromD, E => FromE, F => FromF, G => FromG, H => FromH);
+impl_unzip_iter!(A => FromA, B => FromB, C => FromC, D => FromD, E => FromE, F => FromF, G => FromG, H => FromH, I => FromI);
+impl_unzip_iter!(A => FromA, B => FromB, C => FromC, D => FromD, E => FromE, F => FromF, G => FromG, H => FromH, I => FromI, J => FromJ);
+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);
+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);