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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-17 12:02:58 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-17 12:02:58 +0000 |
commit | 698f8c2f01ea549d77d7dc3338a12e04c11057b9 (patch) | |
tree | 173a775858bd501c378080a10dca74132f05bc50 /library/core/src/iter/adapters/filter_map.rs | |
parent | Initial commit. (diff) | |
download | rustc-698f8c2f01ea549d77d7dc3338a12e04c11057b9.tar.xz rustc-698f8c2f01ea549d77d7dc3338a12e04c11057b9.zip |
Adding upstream version 1.64.0+dfsg1.upstream/1.64.0+dfsg1
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'library/core/src/iter/adapters/filter_map.rs')
-rw-r--r-- | library/core/src/iter/adapters/filter_map.rs | 149 |
1 files changed, 149 insertions, 0 deletions
diff --git a/library/core/src/iter/adapters/filter_map.rs b/library/core/src/iter/adapters/filter_map.rs new file mode 100644 index 000000000..e0d665c9e --- /dev/null +++ b/library/core/src/iter/adapters/filter_map.rs @@ -0,0 +1,149 @@ +use crate::fmt; +use crate::iter::{adapters::SourceIter, FusedIterator, InPlaceIterable}; +use crate::ops::{ControlFlow, Try}; + +/// An iterator that uses `f` to both filter and map elements from `iter`. +/// +/// This `struct` is created by the [`filter_map`] method on [`Iterator`]. See its +/// documentation for more. +/// +/// [`filter_map`]: Iterator::filter_map +/// [`Iterator`]: trait.Iterator.html +#[must_use = "iterators are lazy and do nothing unless consumed"] +#[stable(feature = "rust1", since = "1.0.0")] +#[derive(Clone)] +pub struct FilterMap<I, F> { + iter: I, + f: F, +} +impl<I, F> FilterMap<I, F> { + pub(in crate::iter) fn new(iter: I, f: F) -> FilterMap<I, F> { + FilterMap { iter, f } + } +} + +#[stable(feature = "core_impl_debug", since = "1.9.0")] +impl<I: fmt::Debug, F> fmt::Debug for FilterMap<I, F> { + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + f.debug_struct("FilterMap").field("iter", &self.iter).finish() + } +} + +fn filter_map_fold<T, B, Acc>( + mut f: impl FnMut(T) -> Option<B>, + mut fold: impl FnMut(Acc, B) -> Acc, +) -> impl FnMut(Acc, T) -> Acc { + move |acc, item| match f(item) { + Some(x) => fold(acc, x), + None => acc, + } +} + +fn filter_map_try_fold<'a, T, B, Acc, R: Try<Output = Acc>>( + f: &'a mut impl FnMut(T) -> Option<B>, + mut fold: impl FnMut(Acc, B) -> R + 'a, +) -> impl FnMut(Acc, T) -> R + 'a { + move |acc, item| match f(item) { + Some(x) => fold(acc, x), + None => try { acc }, + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl<B, I: Iterator, F> Iterator for FilterMap<I, F> +where + F: FnMut(I::Item) -> Option<B>, +{ + type Item = B; + + #[inline] + fn next(&mut self) -> Option<B> { + self.iter.find_map(&mut self.f) + } + + #[inline] + fn size_hint(&self) -> (usize, Option<usize>) { + let (_, upper) = self.iter.size_hint(); + (0, upper) // can't know a lower bound, due to the predicate + } + + #[inline] + fn try_fold<Acc, Fold, R>(&mut self, init: Acc, fold: Fold) -> R + where + Self: Sized, + Fold: FnMut(Acc, Self::Item) -> R, + R: Try<Output = Acc>, + { + self.iter.try_fold(init, filter_map_try_fold(&mut self.f, fold)) + } + + #[inline] + fn fold<Acc, Fold>(self, init: Acc, fold: Fold) -> Acc + where + Fold: FnMut(Acc, Self::Item) -> Acc, + { + self.iter.fold(init, filter_map_fold(self.f, fold)) + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl<B, I: DoubleEndedIterator, F> DoubleEndedIterator for FilterMap<I, F> +where + F: FnMut(I::Item) -> Option<B>, +{ + #[inline] + fn next_back(&mut self) -> Option<B> { + #[inline] + fn find<T, B>( + f: &mut impl FnMut(T) -> Option<B>, + ) -> impl FnMut((), T) -> ControlFlow<B> + '_ { + move |(), x| match f(x) { + Some(x) => ControlFlow::Break(x), + None => ControlFlow::CONTINUE, + } + } + + self.iter.try_rfold((), find(&mut self.f)).break_value() + } + + #[inline] + fn try_rfold<Acc, Fold, R>(&mut self, init: Acc, fold: Fold) -> R + where + Self: Sized, + Fold: FnMut(Acc, Self::Item) -> R, + R: Try<Output = Acc>, + { + self.iter.try_rfold(init, filter_map_try_fold(&mut self.f, fold)) + } + + #[inline] + fn rfold<Acc, Fold>(self, init: Acc, fold: Fold) -> Acc + where + Fold: FnMut(Acc, Self::Item) -> Acc, + { + self.iter.rfold(init, filter_map_fold(self.f, fold)) + } +} + +#[stable(feature = "fused", since = "1.26.0")] +impl<B, I: FusedIterator, F> FusedIterator for FilterMap<I, F> where F: FnMut(I::Item) -> Option<B> {} + +#[unstable(issue = "none", feature = "inplace_iteration")] +unsafe impl<I, F> SourceIter for FilterMap<I, F> +where + I: SourceIter, +{ + type Source = I::Source; + + #[inline] + unsafe fn as_inner(&mut self) -> &mut I::Source { + // SAFETY: unsafe function forwarding to unsafe function with the same requirements + unsafe { SourceIter::as_inner(&mut self.iter) } + } +} + +#[unstable(issue = "none", feature = "inplace_iteration")] +unsafe impl<B, I: InPlaceIterable, F> InPlaceIterable for FilterMap<I, F> where + F: FnMut(I::Item) -> Option<B> +{ +} |