use crate::fmt;
use crate::iter::adapters::zip::try_get_unchecked;
use crate::iter::adapters::{SourceIter, TrustedRandomAccess, TrustedRandomAccessNoCoerce};
use crate::iter::{FusedIterator, InPlaceIterable, TrustedFused, TrustedLen, UncheckedIterator};
use crate::num::NonZero;
use crate::ops::Try;
#[must_use = "iterators are lazy and do nothing unless consumed"]
#[stable(feature = "rust1", since = "1.0.0")]
#[derive(Clone)]
pub struct Map<I, F> {
    pub(crate) iter: I,
    f: F,
}
impl<I, F> Map<I, F> {
    pub(in crate::iter) fn new(iter: I, f: F) -> Map<I, F> {
        Map { iter, f }
    }
    pub(crate) fn into_inner(self) -> I {
        self.iter
    }
}
#[stable(feature = "core_impl_debug", since = "1.9.0")]
impl<I: fmt::Debug, F> fmt::Debug for Map<I, F> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.debug_struct("Map").field("iter", &self.iter).finish()
    }
}
fn map_fold<T, B, Acc>(
    mut f: impl FnMut(T) -> B,
    mut g: impl FnMut(Acc, B) -> Acc,
) -> impl FnMut(Acc, T) -> Acc {
    move |acc, elt| g(acc, f(elt))
}
fn map_try_fold<'a, T, B, Acc, R>(
    f: &'a mut impl FnMut(T) -> B,
    mut g: impl FnMut(Acc, B) -> R + 'a,
) -> impl FnMut(Acc, T) -> R + 'a {
    move |acc, elt| g(acc, f(elt))
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<B, I: Iterator, F> Iterator for Map<I, F>
where
    F: FnMut(I::Item) -> B,
{
    type Item = B;
    #[inline]
    fn next(&mut self) -> Option<B> {
        self.iter.next().map(&mut self.f)
    }
    #[inline]
    fn size_hint(&self) -> (usize, Option<usize>) {
        self.iter.size_hint()
    }
    fn try_fold<Acc, G, R>(&mut self, init: Acc, g: G) -> R
    where
        Self: Sized,
        G: FnMut(Acc, Self::Item) -> R,
        R: Try<Output = Acc>,
    {
        self.iter.try_fold(init, map_try_fold(&mut self.f, g))
    }
    fn fold<Acc, G>(self, init: Acc, g: G) -> Acc
    where
        G: FnMut(Acc, Self::Item) -> Acc,
    {
        self.iter.fold(init, map_fold(self.f, g))
    }
    #[inline]
    unsafe fn __iterator_get_unchecked(&mut self, idx: usize) -> B
    where
        Self: TrustedRandomAccessNoCoerce,
    {
        unsafe { (self.f)(try_get_unchecked(&mut self.iter, idx)) }
    }
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<B, I: DoubleEndedIterator, F> DoubleEndedIterator for Map<I, F>
where
    F: FnMut(I::Item) -> B,
{
    #[inline]
    fn next_back(&mut self) -> Option<B> {
        self.iter.next_back().map(&mut self.f)
    }
    fn try_rfold<Acc, G, R>(&mut self, init: Acc, g: G) -> R
    where
        Self: Sized,
        G: FnMut(Acc, Self::Item) -> R,
        R: Try<Output = Acc>,
    {
        self.iter.try_rfold(init, map_try_fold(&mut self.f, g))
    }
    fn rfold<Acc, G>(self, init: Acc, g: G) -> Acc
    where
        G: FnMut(Acc, Self::Item) -> Acc,
    {
        self.iter.rfold(init, map_fold(self.f, g))
    }
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<B, I: ExactSizeIterator, F> ExactSizeIterator for Map<I, F>
where
    F: FnMut(I::Item) -> B,
{
    fn len(&self) -> usize {
        self.iter.len()
    }
    fn is_empty(&self) -> bool {
        self.iter.is_empty()
    }
}
#[stable(feature = "fused", since = "1.26.0")]
impl<B, I: FusedIterator, F> FusedIterator for Map<I, F> where F: FnMut(I::Item) -> B {}
#[unstable(issue = "none", feature = "trusted_fused")]
unsafe impl<I: TrustedFused, F> TrustedFused for Map<I, F> {}
#[unstable(feature = "trusted_len", issue = "37572")]
unsafe impl<B, I, F> TrustedLen for Map<I, F>
where
    I: TrustedLen,
    F: FnMut(I::Item) -> B,
{
}
impl<B, I, F> UncheckedIterator for Map<I, F>
where
    I: UncheckedIterator,
    F: FnMut(I::Item) -> B,
{
    unsafe fn next_unchecked(&mut self) -> B {
        let item = unsafe { self.iter.next_unchecked() };
        (self.f)(item)
    }
}
#[doc(hidden)]
#[unstable(feature = "trusted_random_access", issue = "none")]
unsafe impl<I, F> TrustedRandomAccess for Map<I, F> where I: TrustedRandomAccess {}
#[doc(hidden)]
#[unstable(feature = "trusted_random_access", issue = "none")]
unsafe impl<I, F> TrustedRandomAccessNoCoerce for Map<I, F>
where
    I: TrustedRandomAccessNoCoerce,
{
    const MAY_HAVE_SIDE_EFFECT: bool = true;
}
#[unstable(issue = "none", feature = "inplace_iteration")]
unsafe impl<I, F> SourceIter for Map<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<I: InPlaceIterable, F> InPlaceIterable for Map<I, F> {
    const EXPAND_BY: Option<NonZero<usize>> = I::EXPAND_BY;
    const MERGE_BY: Option<NonZero<usize>> = I::MERGE_BY;
}