| use crate::fmt; |
| use crate::iter::{adapters::SourceIter, FusedIterator, InPlaceIterable}; |
| use crate::ops::Try; |
| |
| /// An iterator that rejects elements while `predicate` returns `true`. |
| /// |
| /// This `struct` is created by the [`skip_while`] method on [`Iterator`]. See its |
| /// documentation for more. |
| /// |
| /// [`skip_while`]: Iterator::skip_while |
| /// [`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 SkipWhile<I, P> { |
| iter: I, |
| flag: bool, |
| predicate: P, |
| } |
| |
| impl<I, P> SkipWhile<I, P> { |
| pub(in crate::iter) fn new(iter: I, predicate: P) -> SkipWhile<I, P> { |
| SkipWhile { iter, flag: false, predicate } |
| } |
| } |
| |
| #[stable(feature = "core_impl_debug", since = "1.9.0")] |
| impl<I: fmt::Debug, P> fmt::Debug for SkipWhile<I, P> { |
| fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { |
| f.debug_struct("SkipWhile").field("iter", &self.iter).field("flag", &self.flag).finish() |
| } |
| } |
| |
| #[stable(feature = "rust1", since = "1.0.0")] |
| impl<I: Iterator, P> Iterator for SkipWhile<I, P> |
| where |
| P: FnMut(&I::Item) -> bool, |
| { |
| type Item = I::Item; |
| |
| #[inline] |
| fn next(&mut self) -> Option<I::Item> { |
| fn check<'a, T>( |
| flag: &'a mut bool, |
| pred: &'a mut impl FnMut(&T) -> bool, |
| ) -> impl FnMut(&T) -> bool + 'a { |
| move |x| { |
| if *flag || !pred(x) { |
| *flag = true; |
| true |
| } else { |
| false |
| } |
| } |
| } |
| |
| let flag = &mut self.flag; |
| let pred = &mut self.predicate; |
| self.iter.find(check(flag, pred)) |
| } |
| |
| #[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, mut init: Acc, mut fold: Fold) -> R |
| where |
| Self: Sized, |
| Fold: FnMut(Acc, Self::Item) -> R, |
| R: Try<Output = Acc>, |
| { |
| if !self.flag { |
| match self.next() { |
| Some(v) => init = fold(init, v)?, |
| None => return try { init }, |
| } |
| } |
| self.iter.try_fold(init, fold) |
| } |
| |
| #[inline] |
| fn fold<Acc, Fold>(mut self, mut init: Acc, mut fold: Fold) -> Acc |
| where |
| Fold: FnMut(Acc, Self::Item) -> Acc, |
| { |
| if !self.flag { |
| match self.next() { |
| Some(v) => init = fold(init, v), |
| None => return init, |
| } |
| } |
| self.iter.fold(init, fold) |
| } |
| } |
| |
| #[stable(feature = "fused", since = "1.26.0")] |
| impl<I, P> FusedIterator for SkipWhile<I, P> |
| where |
| I: FusedIterator, |
| P: FnMut(&I::Item) -> bool, |
| { |
| } |
| |
| #[unstable(issue = "none", feature = "inplace_iteration")] |
| unsafe impl<P, I> SourceIter for SkipWhile<I, P> |
| 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 SkipWhile<I, F> where |
| F: FnMut(&I::Item) -> bool |
| { |
| } |