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impl ParallelExtend for tuple pairs #604

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Oct 30, 2018
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@cuviper cuviper commented Oct 9, 2018

ParallelExtend<(A, B)> and ParallelExtend<Either<L, R>> for tuples
behave like unzip and partition_map respectively. These allow the
possibility of nested unzip and partition_map operations, filling
into more than just two collections. For instance, (A, (B, C)) items
can be unzipped into (Vec<A>, (Vec<B>, Vec<C>)).

Fixes #600.

`ParallelExtend<(A, B)>` and `ParallelExtend<Either<L, R>>` for tuples
behave like `unzip` and `partition_map` respectively.  These allow the
possibility of nested `unzip` and `partition_map` operations, filling
into more than just two collections.  For instance, `(A, (B, C))` items
can be unzipped into `(Vec<A>, (Vec<B>, Vec<C>))`.
@@ -386,3 +395,57 @@ impl<A, B, RA, RB> Reducer<(A, B)> for UnzipReducer<RA, RB>
(self.left.reduce(left.0, right.0), self.right.reduce(left.1, right.1))
}
}


impl<A, B, FromA, FromB> ParallelExtend<(A, B)> for (FromA, FromB)
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FWIW, the standard library does not have an Extend implementation like this, though I think it could. The value there would not be as high though, as there's significantly more magic involved in the parallel implementation.

}
}

impl<L, R, A, B> ParallelExtend<Either<L, R>> for (A, B)
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I think coherence rules would make this impossible for Extend since tuples aren't fundamental -- the either crate can't implement the trait for a generic tuple type. So this is a unique possibility for ParallelExtend!

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Hmm, Rust 1.41's "re-rebalance coherence" would allow this now... 🤔

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bors r+

bors bot added a commit that referenced this pull request Oct 30, 2018
604: impl ParallelExtend for tuple pairs r=nikomatsakis a=cuviper

`ParallelExtend<(A, B)>` and `ParallelExtend<Either<L, R>>` for tuples
behave like `unzip` and `partition_map` respectively.  These allow the
possibility of nested `unzip` and `partition_map` operations, filling
into more than just two collections.  For instance, `(A, (B, C))` items
can be unzipped into `(Vec<A>, (Vec<B>, Vec<C>))`.

Fixes #600.

Co-authored-by: Josh Stone <cuviper@gmail.com>
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bors bot commented Oct 30, 2018

@bors bors bot merged commit e46efd2 into rayon-rs:master Oct 30, 2018
bors bot added a commit that referenced this pull request Apr 1, 2021
802: impl FromParallelIterator for tuple pairs r=nikomatsakis a=cuviper

Like #604 for `ParallelExtend`, implementing `FromParallelIterator` for tuple pairs opens up new possibilities for nesting `collect`. The possibility of short-circuiting into `Result<(T, U), E>` for #801 is particularly motivating.

- `FromParallelIterator<(A, B)> for (FromA, FromB)` works like `unzip`
- `FromParallelIterator<Either<L, R>> for (A, B)` works like `partition_map`


Co-authored-by: Josh Stone <cuviper@gmail.com>
@cuviper cuviper deleted the extend-pairs branch February 25, 2023 17:58
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2 participants