diff --git a/src/libcore/iter/iterator.rs b/src/libcore/iter/iterator.rs index 296fb8733ba6c..a485e2c82bada 100644 --- a/src/libcore/iter/iterator.rs +++ b/src/libcore/iter/iterator.rs @@ -1366,9 +1366,9 @@ pub trait Iterator { /// /// In particular, try to have this call `try_fold()` on the internal parts /// from which this iterator is composed. If multiple calls are needed, - /// the `?` operator be convenient for chaining the accumulator value along, - /// but beware any invariants that need to be upheld before those early - /// returns. This is a `&mut self` method, so iteration needs to be + /// the `?` operator may be convenient for chaining the accumulator value + /// along, but beware any invariants that need to be upheld before those + /// early returns. This is a `&mut self` method, so iteration needs to be /// resumable after hitting an error here. /// /// # Examples @@ -1414,6 +1414,42 @@ pub trait Iterator { Try::from_ok(accum) } + /// An iterator method that applies a fallible function to each item in the + /// iterator, stopping at the first error and returning that error. + /// + /// This can also be thought of as the fallible form of [`for_each()`] + /// or as the stateless version of [`try_fold()`]. + /// + /// [`for_each()`]: #method.for_each + /// [`try_fold()`]: #method.try_fold + /// + /// # Examples + /// + /// ``` + /// #![feature(iterator_try_fold)] + /// use std::fs::rename; + /// use std::io::{stdout, Write}; + /// use std::path::Path; + /// + /// let data = ["no_tea.txt", "stale_bread.json", "torrential_rain.png"]; + /// + /// let res = data.iter().try_for_each(|x| writeln!(stdout(), "{}", x)); + /// assert!(res.is_ok()); + /// + /// let mut it = data.iter().cloned(); + /// let res = it.try_for_each(|x| rename(x, Path::new(x).with_extension("old"))); + /// assert!(res.is_err()); + /// // It short-circuited, so the remaining items are still in the iterator: + /// assert_eq!(it.next(), Some("stale_bread.json")); + /// ``` + #[inline] + #[unstable(feature = "iterator_try_fold", issue = "45594")] + fn try_for_each(&mut self, mut f: F) -> R where + Self: Sized, F: FnMut(Self::Item) -> R, R: Try + { + self.try_fold((), move |(), x| f(x)) + } + /// An iterator method that applies a function, producing a single, final value. /// /// `fold()` takes two arguments: an initial value, and a closure with two @@ -1528,7 +1564,7 @@ pub trait Iterator { fn all(&mut self, mut f: F) -> bool where Self: Sized, F: FnMut(Self::Item) -> bool { - self.try_fold((), move |(), x| { + self.try_for_each(move |x| { if f(x) { LoopState::Continue(()) } else { LoopState::Break(()) } }) == LoopState::Continue(()) @@ -1577,7 +1613,7 @@ pub trait Iterator { Self: Sized, F: FnMut(Self::Item) -> bool { - self.try_fold((), move |(), x| { + self.try_for_each(move |x| { if f(x) { LoopState::Break(()) } else { LoopState::Continue(()) } }) == LoopState::Break(()) @@ -1631,7 +1667,7 @@ pub trait Iterator { Self: Sized, P: FnMut(&Self::Item) -> bool, { - self.try_fold((), move |(), x| { + self.try_for_each(move |x| { if predicate(&x) { LoopState::Break(x) } else { LoopState::Continue(()) } }).break_value()