diff options
Diffstat (limited to '')
-rw-r--r-- | library/core/src/iter/adapters/inspect.rs | 166 |
1 files changed, 166 insertions, 0 deletions
diff --git a/library/core/src/iter/adapters/inspect.rs b/library/core/src/iter/adapters/inspect.rs new file mode 100644 index 000000000..19839fdfe --- /dev/null +++ b/library/core/src/iter/adapters/inspect.rs @@ -0,0 +1,166 @@ +use crate::fmt; +use crate::iter::{adapters::SourceIter, FusedIterator, InPlaceIterable}; +use crate::ops::Try; + +/// An iterator that calls a function with a reference to each element before +/// yielding it. +/// +/// This `struct` is created by the [`inspect`] method on [`Iterator`]. See its +/// documentation for more. +/// +/// [`inspect`]: Iterator::inspect +/// [`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 Inspect<I, F> { + iter: I, + f: F, +} +impl<I, F> Inspect<I, F> { + pub(in crate::iter) fn new(iter: I, f: F) -> Inspect<I, F> { + Inspect { iter, f } + } +} + +#[stable(feature = "core_impl_debug", since = "1.9.0")] +impl<I: fmt::Debug, F> fmt::Debug for Inspect<I, F> { + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + f.debug_struct("Inspect").field("iter", &self.iter).finish() + } +} + +impl<I: Iterator, F> Inspect<I, F> +where + F: FnMut(&I::Item), +{ + #[inline] + fn do_inspect(&mut self, elt: Option<I::Item>) -> Option<I::Item> { + if let Some(ref a) = elt { + (self.f)(a); + } + + elt + } +} + +fn inspect_fold<T, Acc>( + mut f: impl FnMut(&T), + mut fold: impl FnMut(Acc, T) -> Acc, +) -> impl FnMut(Acc, T) -> Acc { + move |acc, item| { + f(&item); + fold(acc, item) + } +} + +fn inspect_try_fold<'a, T, Acc, R>( + f: &'a mut impl FnMut(&T), + mut fold: impl FnMut(Acc, T) -> R + 'a, +) -> impl FnMut(Acc, T) -> R + 'a { + move |acc, item| { + f(&item); + fold(acc, item) + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl<I: Iterator, F> Iterator for Inspect<I, F> +where + F: FnMut(&I::Item), +{ + type Item = I::Item; + + #[inline] + fn next(&mut self) -> Option<I::Item> { + let next = self.iter.next(); + self.do_inspect(next) + } + + #[inline] + fn size_hint(&self) -> (usize, Option<usize>) { + self.iter.size_hint() + } + + #[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, inspect_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, inspect_fold(self.f, fold)) + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl<I: DoubleEndedIterator, F> DoubleEndedIterator for Inspect<I, F> +where + F: FnMut(&I::Item), +{ + #[inline] + fn next_back(&mut self) -> Option<I::Item> { + let next = self.iter.next_back(); + self.do_inspect(next) + } + + #[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, inspect_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, inspect_fold(self.f, fold)) + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl<I: ExactSizeIterator, F> ExactSizeIterator for Inspect<I, F> +where + F: FnMut(&I::Item), +{ + fn len(&self) -> usize { + self.iter.len() + } + + fn is_empty(&self) -> bool { + self.iter.is_empty() + } +} + +#[stable(feature = "fused", since = "1.26.0")] +impl<I: FusedIterator, F> FusedIterator for Inspect<I, F> where F: FnMut(&I::Item) {} + +#[unstable(issue = "none", feature = "inplace_iteration")] +unsafe impl<I, F> SourceIter for Inspect<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<I: InPlaceIterable, F> InPlaceIterable for Inspect<I, F> where F: FnMut(&I::Item) {} |