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use crate::fmt;
use crate::iter::{adapters::SourceIter, FusedIterator, InPlaceIterable};
use crate::ops::{ControlFlow, Try};
#[must_use = "iterators are lazy and do nothing unless consumed"]
#[stable(feature = "rust1", since = "1.0.0")]
#[derive(Clone)]
pub struct FilterMap<I, F> {
iter: I,
f: F,
}
impl<I, F> FilterMap<I, F> {
pub(in crate::iter) fn new(iter: I, f: F) -> FilterMap<I, F> {
FilterMap { iter, f }
}
}
#[stable(feature = "core_impl_debug", since = "1.9.0")]
impl<I: fmt::Debug, F> fmt::Debug for FilterMap<I, F> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_struct("FilterMap").field("iter", &self.iter).finish()
}
}
fn filter_map_fold<T, B, Acc>(
mut f: impl FnMut(T) -> Option<B>,
mut fold: impl FnMut(Acc, B) -> Acc,
) -> impl FnMut(Acc, T) -> Acc {
move |acc, item| match f(item) {
Some(x) => fold(acc, x),
None => acc,
}
}
fn filter_map_try_fold<'a, T, B, Acc, R: Try<Output = Acc>>(
f: &'a mut impl FnMut(T) -> Option<B>,
mut fold: impl FnMut(Acc, B) -> R + 'a,
) -> impl FnMut(Acc, T) -> R + 'a {
move |acc, item| match f(item) {
Some(x) => fold(acc, x),
None => try { acc },
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<B, I: Iterator, F> Iterator for FilterMap<I, F>
where
F: FnMut(I::Item) -> Option<B>,
{
type Item = B;
#[inline]
fn next(&mut self) -> Option<B> {
self.iter.find_map(&mut self.f)
}
#[inline]
fn size_hint(&self) -> (usize, Option<usize>) {
let (_, upper) = self.iter.size_hint();
(0, upper)
}
#[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, filter_map_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, filter_map_fold(self.f, fold))
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<B, I: DoubleEndedIterator, F> DoubleEndedIterator for FilterMap<I, F>
where
F: FnMut(I::Item) -> Option<B>,
{
#[inline]
fn next_back(&mut self) -> Option<B> {
#[inline]
fn find<T, B>(
f: &mut impl FnMut(T) -> Option<B>,
) -> impl FnMut((), T) -> ControlFlow<B> + '_ {
move |(), x| match f(x) {
Some(x) => ControlFlow::Break(x),
None => ControlFlow::CONTINUE,
}
}
self.iter.try_rfold((), find(&mut self.f)).break_value()
}
#[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, filter_map_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, filter_map_fold(self.f, fold))
}
}
#[stable(feature = "fused", since = "1.26.0")]
impl<B, I: FusedIterator, F> FusedIterator for FilterMap<I, F> where F: FnMut(I::Item) -> Option<B> {}
#[unstable(issue = "none", feature = "inplace_iteration")]
unsafe impl<I, F> SourceIter for FilterMap<I, F>
where
I: SourceIter,
{
type Source = I::Source;
#[inline]
unsafe fn as_inner(&mut self) -> &mut I::Source {
unsafe { SourceIter::as_inner(&mut self.iter) }
}
}
#[unstable(issue = "none", feature = "inplace_iteration")]
unsafe impl<B, I: InPlaceIterable, F> InPlaceIterable for FilterMap<I, F> where
F: FnMut(I::Item) -> Option<B>
{
}