| 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) {} |