3 iter::{adapters::SourceIter, FusedIterator, InPlaceIterable},
7 /// An iterator that rejects elements while `predicate` returns `true`.
9 /// This `struct` is created by the [`skip_while`] method on [`Iterator`]. See its
10 /// documentation for more.
12 /// [`skip_while`]: Iterator::skip_while
13 /// [`Iterator`]: trait.Iterator.html
14 #[must_use = "iterators are lazy and do nothing unless consumed"]
15 #[stable(feature = "rust1", since = "1.0.0")]
17 pub struct SkipWhile<I, P> {
23 impl<I, P> SkipWhile<I, P> {
24 pub(in crate::iter) fn new(iter: I, predicate: P) -> SkipWhile<I, P> {
25 SkipWhile { iter, flag: false, predicate }
29 #[stable(feature = "core_impl_debug", since = "1.9.0")]
30 impl<I: fmt::Debug, P> fmt::Debug for SkipWhile<I, P> {
31 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
32 f.debug_struct("SkipWhile").field("iter", &self.iter).field("flag", &self.flag).finish()
36 #[stable(feature = "rust1", since = "1.0.0")]
37 impl<I: Iterator, P> Iterator for SkipWhile<I, P>
39 P: FnMut(&I::Item) -> bool,
44 fn next(&mut self) -> Option<I::Item> {
47 pred: &'a mut impl FnMut(&T) -> bool,
48 ) -> impl FnMut(&T) -> bool + 'a {
50 if *flag || !pred(x) {
59 let flag = &mut self.flag;
60 let pred = &mut self.predicate;
61 self.iter.find(check(flag, pred))
65 fn size_hint(&self) -> (usize, Option<usize>) {
66 let (_, upper) = self.iter.size_hint();
67 (0, upper) // can't know a lower bound, due to the predicate
71 fn try_fold<Acc, Fold, R>(&mut self, mut init: Acc, mut fold: Fold) -> R
74 Fold: FnMut(Acc, Self::Item) -> R,
79 Some(v) => init = fold(init, v)?,
80 None => return try { init },
83 self.iter.try_fold(init, fold)
87 fn fold<Acc, Fold>(mut self, mut init: Acc, mut fold: Fold) -> Acc
89 Fold: FnMut(Acc, Self::Item) -> Acc,
93 Some(v) => init = fold(init, v),
97 self.iter.fold(init, fold)
101 #[stable(feature = "fused", since = "1.26.0")]
102 impl<I, P> FusedIterator for SkipWhile<I, P>
105 P: FnMut(&I::Item) -> bool,
109 #[unstable(issue = "none", feature = "inplace_iteration")]
110 unsafe impl<S: Iterator, P, I: Iterator> SourceIter for SkipWhile<I, P>
112 P: FnMut(&I::Item) -> bool,
113 I: SourceIter<Source = S>,
118 unsafe fn as_inner(&mut self) -> &mut S {
119 // SAFETY: unsafe function forwarding to unsafe function with the same requirements
120 unsafe { SourceIter::as_inner(&mut self.iter) }
124 #[unstable(issue = "none", feature = "inplace_iteration")]
125 unsafe impl<I: InPlaceIterable, F> InPlaceIterable for SkipWhile<I, F> where
126 F: FnMut(&I::Item) -> bool