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New data APIs 0:
ClampedZip iterator machinery (#5573)
This introduces a new temporary `re_query2` crate, which won't ever be published. It will replace the existing `re_query` crate once all the necessary features have been backported. As of this PR, this crate only contains the `ClampedZip` iterator machinery, which is code generated for all the different arities. Since I'm very, _very tired_ of the awful DX of macros, I implemented a very low-tech code generator in the crate itself (`src/bin/clamped_zip.rs`) that just spews the generated code on stdout. That seems like the right complexity-to-maintenance tradeoff, considering that iterator combinators don't really ever change. `ClampedZip` naturally works with more than one required component, finally! - Fixes #4742 - Fixes #2750 Here's an example of one of these combinators: ```rust /// Returns a new [`ClampedZip1x2`] iterator. /// /// The number of elements in a clamped zip iterator corresponds to the number of elements in the /// shortest of its required iterators (`r0`). /// /// Optional iterators (`o0`, `o1`) will repeat their latest values if they happen to be to short /// to be zipped with the shortest of the required iterators. /// /// If an optional iterator is not only too short but actually empty, its associated default function /// (`o0_default_fn`, `o1_default_fn`) will be executed and the resulting value repeated as necessary. pub fn clamped_zip_1x2<R0, O0, O1, D0, D1>( r0: R0, o0: O0, o0_default_fn: D0, o1: O1, o1_default_fn: D1, ) -> ClampedZip1x2<R0::IntoIter, O0::IntoIter, O1::IntoIter, D0, D1> where R0: IntoIterator, O0: IntoIterator, O0::Item: Clone, O1: IntoIterator, O1::Item: Clone, D0: Fn() -> O0::Item, D1: Fn() -> O1::Item, { ClampedZip1x2 { r0: r0.into_iter(), o0: o0.into_iter(), o1: o1.into_iter(), o0_default_fn, o1_default_fn, o0_latest_value: None, o1_latest_value: None, } } /// Implements a clamped zip iterator combinator with 2 required iterators and 2 optional /// iterators. /// /// See [`clamped_zip_1x2`] for more information. pub struct ClampedZip1x2<R0, O0, O1, D0, D1> where R0: Iterator, O0: Iterator, O0::Item: Clone, O1: Iterator, O1::Item: Clone, D0: Fn() -> O0::Item, D1: Fn() -> O1::Item, { r0: R0, o0: O0, o1: O1, o0_default_fn: D0, o1_default_fn: D1, o0_latest_value: Option<O0::Item>, o1_latest_value: Option<O1::Item>, } impl<R0, O0, O1, D0, D1> Iterator for ClampedZip1x2<R0, O0, O1, D0, D1> where R0: Iterator, O0: Iterator, O0::Item: Clone, O1: Iterator, O1::Item: Clone, D0: Fn() -> O0::Item, D1: Fn() -> O1::Item, { type Item = (R0::Item, O0::Item, O1::Item); #[inline] fn next(&mut self) -> Option<Self::Item> { let r0_next = self.r0.next()?; let o0_next = self.o0.next().or(self.o0_latest_value.take()); let o1_next = self.o1.next().or(self.o1_latest_value.take()); self.o0_latest_value = o0_next.clone(); self.o1_latest_value = o1_next.clone(); Some(( r0_next, o0_next.unwrap_or_else(|| (self.o0_default_fn)()), o1_next.unwrap_or_else(|| (self.o1_default_fn)()), )) } } ``` --- Part of a PR series to completely revamp the data APIs in preparation for the removal of instance keys and the introduction of promises: - #5573 - #5574 - #5581 - #5605 - #5606 - #5633 - #5673 - #5679 - #5687 - #5755 - TODO - TODO Builds on top of the static data PR series: - #5534
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