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Merge Merge/MergeBy/MergeJoinBy implementations (v2) #736

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merged 5 commits into from
Sep 20, 2023

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Philippe-Cholet
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Cleaner alternative to the experimental/messy #711. Closes #701.
@phimuemue I would additionally rename InternalMergeJoinBy to MergeBy, making MergeJoinBy an alias of MergeBy instead. But I would like your opinion on this first.
I recently found a way to not add a fourth type to MergeJoinBy (added to the old PR) but another difference is that I do not wrap with MergeFuncT anymore.

@Philippe-Cholet Philippe-Cholet changed the title Merge Merge/MergeBy/MergeJoinBy implementations Merge Merge/MergeBy/MergeJoinBy implementations (v2) Aug 27, 2023
src/merge_join.rs Outdated Show resolved Hide resolved
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@phimuemue What do you think of this new version?
MergeJoinBy do not have a fourth type here, as you thought possible (the small FuncLR trait that make it work seems reasonable to me).

And the trait `OrderingOrBool<L, R>` is now for wrapped functions rather than for `Ordering` and `bool`.

NOTES:
- The new struct `MergeFuncLR<F, T>` is useful to avoid conflicting implementations of `OrderingOrBool<L, R> for F` because the compiler thinks that `F` could implement both `FnMut(&L, &R) -> Ordering` and `FnMut(&L, &R) -> bool`.
- The new trait `FuncLR<L, R>` is useful to be able to infer the Output type `T` without having to add a fourth parameter to `MergeJoinBy`. From what I understand, this is needed because the `FnMut` trait is not fully stabilized yet.
- `OrderingOrBool<L, R>` has a new associated type `Out`, which is useful in `impl Iterator` because otherwise the compiler would complain about `T` be unconstrained.

This successfully pass the tests.
Being now an alias, we can remove various implementations. `FusedIterator` will be inserted back soon.

We don't need `MergePredicate<T>` anymore because we use two new implementations of `OrderingOrBool<T, T>`.
`I` and `J` are fused by `InternalMergeJoinBy` so we don't need them to implement `FusedIterator`.
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Rebased after recent #751.

src/merge_join.rs Outdated Show resolved Hide resolved
Apparently not needed anymore.
@jswrenn jswrenn added this to the next milestone Sep 20, 2023
@jswrenn jswrenn added this pull request to the merge queue Sep 20, 2023
Merged via the queue into rust-itertools:master with commit 6ffdac1 Sep 20, 2023
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@Philippe-Cholet
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That feature was quite a ride for me. 🎉

@jswrenn Note that you are mixing different PRs with the "next" milestone.

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jswrenn commented Sep 20, 2023

What do you mean by "mixing"?

We use the next milestone to keep track of highlights that should be noted in the changelog. (Caveat: We haven't been very consistent about doing so, lately.)

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Just that old PRs of 0.11 are with the new ones, which I noticed and found weird but if it's not an issue then case closed.

@Philippe-Cholet Philippe-Cholet deleted the issue-701-part2-v2 branch September 20, 2023 15:19
@jswrenn jswrenn mentioned this pull request Nov 14, 2023
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Merge MergeBy and MergeJoinBy
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