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use core::{
cmp::Ordering,
iter::{
Chain, Cloned, Copied, Cycle, Enumerate, FlatMap, Fuse, Inspect, Map, Peekable, Rev, Take,
},
num::NonZeroUsize,
};
use crate::NonEmpty;
macro_rules! unwrap {
($expr:expr) => {
match $expr {
Some(it) => it,
// Safety:
// - NonEmpty<impl Iterator> is only constructed from known NonEmpty items
// - NonEmpty<impl Iterator> does give out mutable access to the inner iterator
// (so it always has one element)
None => unsafe { crate::unreachable() },
}
};
}
/// Methods on [`Iterator`]s with a non-empty invariant.
///
/// See [`Self::relax`] to access the normal iterator inside.
impl<I> NonEmpty<I>
where
I: Iterator,
{
/// [`NonEmpty`] version of [`Iterator::next`].
/// ```
/// # use nunny::{vec};
/// let v = vec![1, 2, 3];
/// let _: Option<&u8> = v.iter().next();
/// // ^ normally you have to handle the empty case
/// let _: &u8 = v.iter_ne().first();
/// // ^ but we know there is at least one element
/// ```
pub fn first(mut self) -> I::Item {
unwrap!(self.inner.next())
}
/// [`NonEmpty`] version of [`Iterator::last`].
/// ```
/// # use nunny::{vec};
/// let v = vec![1, 2, 3];
/// let _: Option<&u8> = v.iter().last();
/// // ^ normally you have to handle the empty case
/// let _: &u8 = v.iter_ne().last();
/// // ^ but we know there is at least one element
/// ```
pub fn last(self) -> I::Item {
unwrap!(self.inner.last())
}
/// [`NonEmpty`] version of [`Iterator::map`].
/// ```
/// # use nunny::{slice};
/// let iter = slice![1, 2, 3].iter_ne();
/// assert_eq!(
/// iter.map(|it| *it * 2).last(),
/// // ^ the invariant is maintained
/// // so we _know_ there's a last element
/// 6
/// );
/// ```
pub fn map<B, F>(self, f: F) -> NonEmpty<Map<I, F>>
where
F: FnMut(I::Item) -> B,
{
NonEmpty {
inner: self.inner.map(f),
}
}
/// [`NonEmpty`] version of [`Iterator::chain`].
/// ```
/// # use nunny::{slice};
/// let iter = slice![1, 2].iter_ne();
/// assert_eq!(
/// iter.chain(&[3]).last(),
/// // ^ the invariant is maintained
/// // so we _know_ there's a last element
/// &3
/// );
/// ```
pub fn chain<U>(self, other: U) -> NonEmpty<Chain<I, <U as IntoIterator>::IntoIter>>
where
U: IntoIterator<Item = I::Item>,
{
NonEmpty {
inner: self.inner.chain(other),
}
}
/// [`NonEmpty`] version of [`Iterator::enumerate`].
/// ```
/// # use nunny::{slice};
/// let iter = slice!['a', 'b'].iter_ne();
/// assert_eq!(
/// iter.enumerate().last(),
/// // ^ the invariant is maintained
/// // so we _know_ there's a last element
/// (1, &'b')
/// );
/// ```
pub fn enumerate(self) -> NonEmpty<Enumerate<I>> {
NonEmpty {
inner: self.inner.enumerate(),
}
}
/// [`NonEmpty`] version of [`Iterator::peekable`], allowing you to use
/// [`Self::peek`] and [`Self::peek_mut`]
/// ```
/// # use nunny::{vec, NonEmpty};
/// let mut peek_me = vec!['a', 'b'].into_iter_ne().peekable();
/// assert_eq!(
/// *peek_me.peek(),
/// 'a'
/// );
/// *peek_me.peek_mut() = 'b';
/// assert_eq!(
/// peek_me.collect_vec(),
/// ['b', 'b']
/// );
/// ```
pub fn peekable(self) -> NonEmpty<Peekable<I>> {
NonEmpty {
inner: self.inner.peekable(),
}
}
/// [`NonEmpty`] version of [`Iterator::take`].
///
/// Note that `n` cannot be zero, to maintain the [`NonEmpty`] invariant.
///
/// ```
/// # use nunny::{slice, nonzero};
/// let iter = slice!['a', 'b'].iter_ne();
/// assert_eq!(
/// iter.take(nonzero!(1)).last(),
/// // ^ compile time checked
/// &'a'
/// )
/// ```
pub fn take(self, n: NonZeroUsize) -> NonEmpty<Take<I>> {
NonEmpty {
inner: self.inner.take(n.get()),
}
}
// pub fn flat_map
/// [`NonEmpty`] version of [`Iterator::flatten`].
///
/// Note that the inner items must also be [`NonEmpty`], to maintain the invariant.
/// ```
/// use nunny::{vec};
/// let nested = vec![vec![1], vec![2, 3]];
/// assert_eq!(
/// nested.into_iter_ne().flatten().collect_vec(),
/// [1, 2, 3],
/// );
/// ```
#[allow(clippy::type_complexity)]
pub fn flatten<II, T>(self) -> NonEmpty<FlatMap<I, II, fn(I::Item) -> II>>
where
I: Iterator<Item = NonEmpty<II>>,
// ^ each item is nonempty
II: IntoIterator<Item = T>,
// TODO(aatifsyed): a trait NonEmptyIterator would make this more ergonomic
// See commit history for an attempt
{
NonEmpty {
inner: self.inner.flat_map(|it| it.inner),
}
}
/// [`NonEmpty`] version of [`Iterator::fuse`].
pub fn fuse(self) -> NonEmpty<Fuse<I>> {
NonEmpty {
inner: self.inner.fuse(),
}
}
/// [`NonEmpty`] version of [`Iterator::inspect`].
pub fn inspect<F>(self, f: F) -> NonEmpty<Inspect<I, F>>
where
F: FnMut(&I::Item),
{
NonEmpty {
inner: self.inner.inspect(f),
}
}
/// [`NonEmpty`] version of [`Iterator::reduce`].
/// ```
/// # use nunny::{vec};
/// # use core::cmp::min;
/// let v = vec![1, 2, 3];
/// let _: Option<&u8> = v.iter().reduce(min);
/// // ^ normally you have to handle the empty case
/// let _: &u8 = v.iter_ne().reduce(min);
/// // ^ but we know there is at least one element
/// ```
pub fn reduce<F>(self, f: F) -> I::Item
where
F: FnMut(I::Item, I::Item) -> I::Item,
{
unwrap!(self.inner.reduce(f))
}
/// [`NonEmpty`] version of [`Iterator::max`].
/// ```
/// # use nunny::{vec};
/// let v = vec![1, 2, 3];
/// let _: Option<&u8> = v.iter().max();
/// // ^ normally you have to handle the empty case
/// let _: &u8 = v.iter_ne().max();
/// // ^ but we know there is at least one element
/// ```
pub fn max(self) -> I::Item
where
I::Item: Ord,
{
unwrap!(self.inner.max())
}
/// [`NonEmpty`] version of [`Iterator::min`].
/// ```
/// # use nunny::{vec};
/// let v = vec![1, 2, 3];
/// let _: Option<&u8> = v.iter().min();
/// // ^ normally you have to handle the empty case
/// let _: &u8 = v.iter_ne().min();
/// // ^ but we know there is at least one element
/// ```
pub fn min(self) -> I::Item
where
I::Item: Ord,
{
unwrap!(self.inner.min())
}
/// [`NonEmpty`] version of [`Iterator::max_by_key`].
pub fn max_by_key<B, F>(self, f: F) -> I::Item
where
B: Ord,
F: FnMut(&I::Item) -> B,
{
unwrap!(self.inner.max_by_key(f))
}
/// [`NonEmpty`] version of [`Iterator::max_by`].
pub fn max_by<F>(self, compare: F) -> I::Item
where
F: FnMut(&I::Item, &I::Item) -> Ordering,
{
unwrap!(self.inner.max_by(compare))
}
/// [`NonEmpty`] version of [`Iterator::min_by_key`].
pub fn min_by_key<B, F>(self, f: F) -> I::Item
where
B: Ord,
F: FnMut(&I::Item) -> B,
{
unwrap!(self.inner.min_by_key(f))
}
/// [`NonEmpty`] version of [`Iterator::min_by`].
pub fn min_by<F>(self, compare: F) -> I::Item
where
F: FnMut(&I::Item, &I::Item) -> Ordering,
{
unwrap!(self.inner.min_by(compare))
}
/// [`NonEmpty`] version of [`Iterator::rev`].
pub fn rev(self) -> NonEmpty<Rev<I>>
where
I: DoubleEndedIterator,
{
NonEmpty {
inner: self.inner.rev(),
}
}
/// [`NonEmpty`] version of [`Iterator::unzip`].
#[cfg(feature = "alloc")]
#[cfg_attr(docsrs, doc(cfg(feature = "alloc")))]
pub fn unzip_vec<A, B>(self) -> (crate::Vec<A>, crate::Vec<B>)
where
I: Iterator<Item = (A, B)>,
{
let (a, b) = self.inner.unzip();
// Safety:
// - NonEmpty<impl Iterator> is only constructed from known NonEmpty items
// - NonEmpty<impl Iterator> does not allow mutable access to the inner iterator
// (so it always has one element)
unsafe { (crate::Vec::new_unchecked(a), crate::Vec::new_unchecked(b)) }
}
/// [`NonEmpty`] version of [`Iterator::copied`].
pub fn copied<'a, T>(self) -> NonEmpty<Copied<I>>
where
T: 'a + Copy,
I: Iterator<Item = &'a T>,
{
NonEmpty {
inner: self.inner.copied(),
}
}
/// [`NonEmpty`] version of [`Iterator::cloned`].
pub fn cloned<'a, T>(self) -> NonEmpty<Cloned<I>>
where
T: 'a + Clone,
I: Iterator<Item = &'a T>,
{
NonEmpty {
inner: self.inner.cloned(),
}
}
/// [`NonEmpty`] version of [`Iterator::cycle`].
pub fn cycle(self) -> NonEmpty<Cycle<I>>
where
I: Clone,
{
NonEmpty {
inner: self.inner.cycle(),
}
}
/// Remove the [`NonEmpty`] wrapper, allowing you to access normal iterator
/// methods like [`Iterator::filter`].
#[doc(alias = "into_iter")]
#[doc(alias = "into_inner")]
pub fn relax(self) -> I {
self.inner
}
/// Collect this iterator into a [`NonEmpty<Vec>`].
#[cfg(feature = "alloc")]
#[cfg_attr(docsrs, doc(cfg(feature = "alloc")))]
pub fn collect_vec(self) -> crate::Vec<I::Item> {
// Safety:
// - NonEmpty<impl Iterator> is only constructed from known NonEmpty items
// - NonEmpty<impl Iterator> does not allow mutable access to the inner iterator
// (so it always has one element)
unsafe { crate::Vec::new_unchecked(self.inner.collect()) }
}
/// Collect [`Ok`] items into a [`NonEmpty<Vec>`], short-circuiting on [`Err`].
#[cfg(feature = "alloc")]
#[cfg_attr(docsrs, doc(cfg(feature = "alloc")))]
pub fn try_collect_vec<T, E>(self) -> Result<crate::Vec<T>, E>
where
I: Iterator<Item = Result<T, E>>,
{
match self.inner.collect() {
// Safety:
// - NonEmpty<impl Iterator> is only constructed from known NonEmpty items
// - NonEmpty<impl Iterator> does not allow mutable access to the inner iterator
// (so it always has one element)
Ok(it) => Ok(unsafe { crate::Vec::new_unchecked(it) }),
Err(e) => Err(e),
}
}
}
impl<I> NonEmpty<Peekable<I>>
where
I: Iterator,
{
/// Peek this [`NonEmpty`] iterator, without advancing it.
///
/// See [`Self::peekable`].
pub fn peek(&mut self) -> &I::Item {
unwrap!(self.inner.peek())
}
/// Peek and modify this [`NonEmpty`] iterator, without advancing it.
///
/// See [`Self::peekable`].
pub fn peek_mut(&mut self) -> &mut I::Item {
unwrap!(self.inner.peek_mut())
}
}