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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/scan.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/scan.rs')
-rw-r--r-- | library/core/src/iter/adapters/scan.rs | 110 |
1 files changed, 110 insertions, 0 deletions
diff --git a/library/core/src/iter/adapters/scan.rs b/library/core/src/iter/adapters/scan.rs new file mode 100644 index 000000000..80bfd2231 --- /dev/null +++ b/library/core/src/iter/adapters/scan.rs @@ -0,0 +1,110 @@ +use crate::fmt; +use crate::iter::{adapters::SourceIter, InPlaceIterable}; +use crate::ops::{ControlFlow, Try}; + +/// An iterator to maintain state while iterating another iterator. +/// +/// This `struct` is created by the [`scan`] method on [`Iterator`]. See its +/// documentation for more. +/// +/// [`scan`]: Iterator::scan +/// [`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 Scan<I, St, F> { + iter: I, + f: F, + state: St, +} + +impl<I, St, F> Scan<I, St, F> { + pub(in crate::iter) fn new(iter: I, state: St, f: F) -> Scan<I, St, F> { + Scan { iter, state, f } + } +} + +#[stable(feature = "core_impl_debug", since = "1.9.0")] +impl<I: fmt::Debug, St: fmt::Debug, F> fmt::Debug for Scan<I, St, F> { + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + f.debug_struct("Scan").field("iter", &self.iter).field("state", &self.state).finish() + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl<B, I, St, F> Iterator for Scan<I, St, F> +where + I: Iterator, + F: FnMut(&mut St, I::Item) -> Option<B>, +{ + type Item = B; + + #[inline] + fn next(&mut self) -> Option<B> { + let a = self.iter.next()?; + (self.f)(&mut self.state, a) + } + + #[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 scan function + } + + #[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>, + { + fn scan<'a, T, St, B, Acc, R: Try<Output = Acc>>( + state: &'a mut St, + f: &'a mut impl FnMut(&mut St, T) -> Option<B>, + mut fold: impl FnMut(Acc, B) -> R + 'a, + ) -> impl FnMut(Acc, T) -> ControlFlow<R, Acc> + 'a { + move |acc, x| match f(state, x) { + None => ControlFlow::Break(try { acc }), + Some(x) => ControlFlow::from_try(fold(acc, x)), + } + } + + let state = &mut self.state; + let f = &mut self.f; + self.iter.try_fold(init, scan(state, f, fold)).into_try() + } + + #[inline] + fn fold<Acc, Fold>(mut self, init: Acc, fold: Fold) -> Acc + where + Self: Sized, + Fold: FnMut(Acc, Self::Item) -> Acc, + { + #[inline] + fn ok<B, T>(mut f: impl FnMut(B, T) -> B) -> impl FnMut(B, T) -> Result<B, !> { + move |acc, x| Ok(f(acc, x)) + } + + self.try_fold(init, ok(fold)).unwrap() + } +} + +#[unstable(issue = "none", feature = "inplace_iteration")] +unsafe impl<St, F, I> SourceIter for Scan<I, St, 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<St, F, B, I: InPlaceIterable> InPlaceIterable for Scan<I, St, F> where + F: FnMut(&mut St, I::Item) -> Option<B> +{ +} |