flatk 0.5.2

use super::*;
use std::convert::{AsMut, AsRef};

/// `UniChunked` Assigns a stride `N` to the specified collection.
///
/// # Example
///
/// ```rust
/// use flatk::*;
/// let s = Chunked2::from_flat(vec![1,2,3,4,5,6]);
/// let mut iter = s.iter();
/// assert_eq!(Some(&[1,2]), iter.next());
/// assert_eq!(Some(&[3,4]), iter.next());
/// assert_eq!(Some(&[5,6]), iter.next());
/// assert_eq!(None, iter.next());
/// ```
#[derive(Copy, Clone, PartialEq, Debug)]
pub struct UniChunked<S, N> {
    pub data: S,
    pub chunk_size: N,
}

impl<T: bytemuck::Pod, N: Default + Array<T>> UniChunked<Vec<T>, U<N>> {
    /// Create a `UniChunked` collection from a `Vec` of arrays.
    ///
    /// # Example
    ///
    /// ```
    /// use flatk::*;
    /// let v = vec![[1,2,3],[4,5,6],[7,8,9]];
    /// let c = Chunked3::from_array_vec(v);
    /// assert_eq!(c.data(), &vec![1,2,3,4,5,6,7,8,9]);
    /// ```
    #[inline]
    pub fn from_array_vec(data: Vec<N::Array>) -> UniChunked<Vec<T>, U<N>> {
        // SAFETY: The reinterpret below is safe because T is constrained to be of plain old data
        // type Pod.
        UniChunked {
            chunk_size: Default::default(),
            data: unsafe { reinterpret::reinterpret_vec(data) },
        }
    }
}

impl<'a, T: bytemuck::Pod, N: Default + Array<T>> UniChunked<&'a [T], U<N>> {
    /// Create a `UniChunked` collection from a slice of arrays.
    ///
    /// # Example
    ///
    /// ```
    /// use flatk::*;
    /// let v = vec![[1,2,3],[4,5,6],[7,8,9]];
    /// let c = Chunked3::from_array_vec(v.clone());
    /// assert_eq!(c.data(), &[1,2,3,4,5,6,7,8,9]);
    /// ```
    #[inline]
    pub fn from_array_slice(data: &[N::Array]) -> UniChunked<&[T], U<N>> {
        UniChunked {
            chunk_size: Default::default(),
            data: bytemuck::cast_slice(data),
        }
    }
}

impl<'a, T: bytemuck::Pod, N: Default + Array<T>> UniChunked<&'a mut [T], U<N>> {
    /// Create a `UniChunked` collection from a mutable slice of arrays.
    ///
    /// # Example
    ///
    /// ```
    /// use flatk::*;
    /// let mut v = vec![[1,2,3],[4,5,6],[7,8,9]];
    /// let c = Chunked3::from_array_slice_mut(v.as_mut_slice());
    /// assert_eq!(c.data(), &mut [1,2,3,4,5,6,7,8,9]);
    /// ```
    #[inline]
    pub fn from_array_slice_mut(data: &'a mut [N::Array]) -> UniChunked<&'a mut [T], U<N>> {
        UniChunked {
            chunk_size: Default::default(),
            data: bytemuck::cast_slice_mut(data),
        }
    }
}

impl<S, N: Copy> UniChunked<S, N> {
    #[inline]
    pub fn view<'a>(&'a self) -> UniChunked<S::Type, N>
    where
        S: View<'a>,
    {
        UniChunked {
            data: self.data.view(),
            chunk_size: self.chunk_size,
        }
    }
    #[inline]
    fn view_mut<'a>(&'a mut self) -> UniChunked<S::Type, N>
    where
        S: ViewMut<'a>,
    {
        UniChunked {
            data: self.data.view_mut(),
            chunk_size: self.chunk_size,
        }
    }
}

impl<S, N> UniChunked<S, U<N>>
where
    S: Set,
    N: Array<<S as Set>::Elem>,
    <S as Set>::Elem: bytemuck::Pod,
{
    /// Convert this `UniChunked` collection into arrays.
    ///
    /// # Example
    ///
    /// ```
    /// use flatk::*;
    /// let mut v = vec![[1,2,3],[4,5,6],[7,8,9]];
    ///
    /// // Convert to and from a `Vec` of arrays.
    /// let v_new = Chunked3::from_array_vec(v.clone()).into_arrays();
    /// assert_eq!(v.clone(), v_new);
    ///
    /// // Convert to and from an immutable slice of arrays.
    /// let v_new = Chunked3::from_array_slice(v.as_slice()).into_arrays();
    /// assert_eq!(v.as_slice(), v_new);
    ///
    /// // Convert to and from a mutable slice of arrays.
    /// let mut v_exp = v.clone();
    /// let v_result = Chunked3::from_array_slice_mut(v.as_mut_slice()).into_arrays();
    /// assert_eq!(v_exp.as_mut_slice(), v_result);
    /// ```
    #[inline]
    pub fn into_arrays(self) -> S::Output
    where
        S: ReinterpretAsGrouped<N>,
    {
        ReinterpretAsGrouped::<N>::reinterpret_as_grouped(self.into_inner())
    }
    #[inline]
    pub fn as_mut_arrays<'a>(&'a mut self) -> <&'a mut S as ReinterpretAsGrouped<N>>::Output
    where
        &'a mut S: ReinterpretAsGrouped<N>,
    {
        ReinterpretAsGrouped::<N>::reinterpret_as_grouped(self.data_mut())
    }
    #[inline]
    pub fn as_arrays<'a>(&'a self) -> <&'a S as ReinterpretAsGrouped<N>>::Output
    where
        &'a S: ReinterpretAsGrouped<N>,
    {
        ReinterpretAsGrouped::<N>::reinterpret_as_grouped(self.data())
    }
}

// Note: These must be separate in order to avoid conflict with standard library.
impl<T: Clone + bytemuck::Pod, N: Array<T> + Unsigned> From<UniChunked<Vec<T>, U<N>>>
    for Vec<N::Array>
{
    #[inline]
    fn from(val: UniChunked<Vec<T>, U<N>>) -> Self {
        val.into_arrays()
    }
}

impl<'a, T: Clone + bytemuck::Pod, N: Array<T> + Unsigned> From<UniChunked<&'a [T], U<N>>>
    for &'a [N::Array]
{
    #[inline]
    fn from(val: UniChunked<&'a [T], U<N>>) -> Self {
        val.into_arrays()
    }
}

impl<'a, T: Clone + bytemuck::Pod, N: Array<T> + Unsigned> From<UniChunked<&'a mut [T], U<N>>>
    for &'a mut [N::Array]
{
    #[inline]
    fn from(val: UniChunked<&'a mut [T], U<N>>) -> Self {
        val.into_arrays()
    }
}

/// Define aliases for common uniform chunked types.
pub type ChunkedN<S> = UniChunked<S, usize>;
pub type Chunked9<S> = UniChunked<S, U9>;
pub type Chunked8<S> = UniChunked<S, U8>;
pub type Chunked7<S> = UniChunked<S, U7>;
pub type Chunked6<S> = UniChunked<S, U6>;
pub type Chunked5<S> = UniChunked<S, U5>;
pub type Chunked4<S> = UniChunked<S, U4>;
pub type Chunked3<S> = UniChunked<S, U3>;
pub type Chunked2<S> = UniChunked<S, U2>;
pub type Chunked1<S> = UniChunked<S, U1>;

/*
 * A uniform way to get the chunk size from a unichunked collection with dynamically or statically
 * determined chunk size.
 */

pub trait Dimension: Copy {
    fn value(self) -> usize;
}

impl<N: Unsigned + Copy> Dimension for U<N> {
    #[inline]
    fn value(self) -> usize {
        N::to_usize()
    }
}

impl Dimension for usize {
    #[inline]
    fn value(self) -> usize {
        self
    }
}

impl<S, N: Dimension> ChunkSize for UniChunked<S, N> {
    /// Get the size of each chunk in this collection.
    #[inline]
    fn chunk_size(&self) -> usize {
        self.chunk_size.value()
    }
}

impl<S: ChunkSize, N: Dimension> UniChunked<S, N> {
    #[inline]
    pub fn inner_chunk_size(&self) -> usize {
        self.data.chunk_size()
    }
}

impl<S, N> UniChunked<S, N> {
    /// Get a immutable reference to the underlying data.
    ///
    /// # Example
    ///
    /// ```rust
    /// use flatk::*;
    /// let v = vec![1,2,3,4,5,6];
    /// let s = Chunked3::from_flat(v.clone());
    /// assert_eq!(&v, s.data());
    /// ```
    #[inline]
    pub fn data(&self) -> &S {
        &self.data
    }
    /// Get a mutable reference to the underlying data.
    ///
    /// # Example
    ///
    /// ```rust
    /// use flatk::*;
    /// let mut v = vec![1,2,3,4,5,6];
    /// let mut s = Chunked3::from_flat(v.clone());
    /// v[2] = 100;
    /// s.data_mut()[2] = 100;
    /// assert_eq!(&v, s.data());
    /// ```
    #[inline]
    pub fn data_mut(&mut self) -> &mut S {
        &mut self.data
    }
}

impl<S: Default, N: Default> UniChunked<S, U<N>> {
    /// Create an empty `UniChunked` collection that groups elements into `N`
    /// sized chunks.
    ///
    /// # Example
    ///
    /// ```rust
    /// use flatk::*;
    /// let mut s = Chunked3::<Vec<usize>>::new();
    /// assert_eq!(s, Chunked3::from_flat(Vec::new()));
    /// s.push([1,2,3]);
    /// let mut iter = s.iter();
    /// assert_eq!(Some(&[1,2,3]), iter.next());
    /// assert_eq!(None, iter.next());
    /// ```
    #[inline]
    pub fn new() -> Self {
        UniChunked {
            chunk_size: Default::default(), // Zero sized type.
            data: S::default(),
        }
    }
}

impl<S: Set, N: Unsigned + Default> UniChunked<S, U<N>> {
    /// Create a `UniChunked` collection that groups the elements of the
    /// original set into uniformly sized groups at compile time.
    ///
    /// # Example
    ///
    /// ```rust
    /// use flatk::*;
    /// let s = Chunked3::from_flat(vec![1,2,3,4,5,6]);
    /// let mut iter = s.iter();
    /// assert_eq!(Some(&[1,2,3]), iter.next());
    /// assert_eq!(Some(&[4,5,6]), iter.next());
    /// assert_eq!(None, iter.next());
    /// ```
    #[inline]
    pub fn from_flat(data: S) -> Self {
        assert_eq!(data.len() % N::to_usize(), 0);
        UniChunked {
            chunk_size: Default::default(), // Zero sized type.
            data,
        }
    }
}

impl<S, N> UniChunked<S, N> {
    /// Convert this `UniChunked` collection into its inner representation.
    #[inline]
    pub fn into_inner(self) -> S {
        self.data
    }
}

impl<S: Default> ChunkedN<S> {
    /// Create an empty `UniChunked` collection that groups elements into `n`
    /// sized chunks.
    ///
    /// # Example
    ///
    /// ```rust
    /// use flatk::*;
    /// let mut s = ChunkedN::<Vec<_>>::with_stride(3);
    /// s.push(&[1,2,3][..]);
    /// let mut iter = s.iter();
    /// assert_eq!(Some(&[1,2,3][..]), iter.next());
    /// assert_eq!(None, iter.next());
    /// ```
    #[inline]
    pub fn with_stride(n: usize) -> Self {
        UniChunked {
            chunk_size: n,
            data: S::default(),
        }
    }
}

impl<S: Set> ChunkedN<S> {
    /// Create a `UniChunked` collection that groups the elements of the
    /// original set into uniformly sized groups at compile time.
    ///
    /// # Example
    ///
    /// ```rust
    /// use flatk::*;
    /// let s = ChunkedN::from_flat_with_stride(3, vec![1,2,3,4,5,6]);
    /// let mut iter = s.iter();
    /// assert_eq!(Some(&[1,2,3][..]), iter.next());
    /// assert_eq!(Some(&[4,5,6][..]), iter.next());
    /// assert_eq!(None, iter.next());
    /// ```
    #[inline]
    pub fn from_flat_with_stride(n: usize, data: S) -> Self {
        assert_eq!(data.len() % n, 0);
        UniChunked {
            chunk_size: n,
            data,
        }
    }
}

impl<S, N> UniChunked<S, N> {
    /// This function panics if `src` has doesn't have a length equal to `self.len()*N::value()`.
    pub fn copy_from_flat<T>(&mut self, src: &[T])
    where
        T: Copy,
        S: AsMut<[T]>,
    {
        let data = self.data.as_mut();
        assert_eq!(src.len(), data.len());
        data.copy_from_slice(src);
    }

    /// This function panics if `src` has doesn't have a length equal to `self.len()*N::value()`.
    pub fn clone_from_flat<T>(&mut self, src: &[T])
    where
        T: Clone,
        S: AsMut<[T]>,
    {
        let data = self.data.as_mut();
        assert_eq!(src.len(), data.len());
        data.clone_from_slice(src);
    }
}

impl<S, N> UniChunked<S, U<N>>
where
    S: Set + UniChunkable<N>,
    N: Unsigned,
{
    /// This function panics if `src` has doesn't have a length equal to `self.len()`.
    pub fn copy_from_arrays(&mut self, src: &[N::Array])
    where
        N: Array<<S as Set>::Elem>,
        <S as Set>::Elem: Copy + bytemuck::Pod,
        S: AsMut<[<S as Set>::Elem]>,
    {
        assert_eq!(src.len(), self.len());
        self.data
            .as_mut()
            .copy_from_slice(bytemuck::cast_slice(src));
    }
    /// This function panics if `src` has doesn't have a length equal to `self.len()`.
    pub fn clone_from_arrays(&mut self, src: &[N::Array])
    where
        N: Array<<S as Set>::Elem>,
        <S as Set>::Elem: Clone + bytemuck::Pod,
        S: AsMut<[<S as Set>::Elem]>,
    {
        assert_eq!(src.len(), self.len());
        self.data
            .as_mut()
            .clone_from_slice(bytemuck::cast_slice(src));
    }
}

impl<T, N: Unsigned + Array<T>> UniChunked<Vec<T>, U<N>> {
    pub fn reserve(&mut self, new_length: usize) {
        self.data.reserve(new_length * N::to_usize());
    }
}

impl<T> ChunkedN<Vec<T>> {
    pub fn reserve(&mut self, new_length: usize) {
        self.data.reserve(new_length * self.chunk_size);
    }
}

impl<T, N: Unsigned + Array<T>> UniChunked<Vec<T>, U<N>>
where
    <N as Array<T>>::Array: Clone,
{
    pub fn resize(&mut self, new_length: usize, default: N::Array)
    where
        T: PushArrayToVec<N> + Clone,
    {
        self.reserve(new_length);
        for _ in 0..new_length {
            PushArrayToVec::<N>::push_to_vec(default, &mut self.data);
        }
    }
}

impl<T> ChunkedN<Vec<T>> {
    pub fn resize(&mut self, new_length: usize, default: &[T])
    where
        T: Clone,
    {
        self.reserve(new_length);
        for _ in 0..new_length {
            self.data.extend_from_slice(default);
        }
    }
}

impl<T, N> UniChunked<Vec<T>, U<N>>
where
    N: Array<T>,
    T: Clone + bytemuck::Pod,
{
    /// Extend this chunked `Vec` from a slice of arrays.
    ///
    /// # Example
    ///
    /// ```rust
    /// use flatk::*;
    /// let mut s = Chunked2::from_flat(vec![0,1,2,3]);
    /// s.extend_from_slice(&[[4,5], [6,7]]);
    /// assert_eq!(s.data(), &vec![0,1,2,3,4,5,6,7]);
    /// ```
    pub fn extend_from_slice(&mut self, slice: &[N::Array]) {
        self.data.extend_from_slice(bytemuck::cast_slice(slice));
    }
}

/// An implementation of `Set` for a `UniChunked` collection of any type that
/// can be grouped as `N` sub-elements.
impl<S: Set + UniChunkable<N>, N: Unsigned> Set for UniChunked<S, U<N>> {
    type Elem = S::Chunk;
    type Atom = S::Atom;

    /// Compute the length of this `UniChunked` collection as the number of
    /// grouped elements in the set.
    ///
    /// # Example
    ///
    /// ```rust
    /// use flatk::*;
    /// let s = UniChunked::<_, U2>::from_flat(vec![0,1,2,3,4,5]);
    /// assert_eq!(s.len(), 3);
    /// let s = UniChunked::<_, U3>::from_flat(vec![0,1,2,3,4,5]);
    /// assert_eq!(s.len(), 2);
    /// ```
    #[inline]
    fn len(&self) -> usize {
        self.data.len() / N::to_usize()
    }
}

/// An implementation of `Set` for a `UniChunked` collection of any type that
/// can be grouped into sub-elements whose size is determined at run-time.
impl<S: Set> Set for ChunkedN<S> {
    type Elem = Vec<S::Elem>;
    type Atom = S::Atom;

    /// Compute the length of this `UniChunked` collection as the number of
    /// grouped elements in the set.
    ///
    /// # Example
    ///
    /// ```rust
    /// use flatk::*;
    /// let s = ChunkedN::from_flat_with_stride(2, vec![0,1,2,3,4,5]);
    /// assert_eq!(s.len(), 3);
    /// let s = ChunkedN::from_flat_with_stride(3, vec![0,1,2,3,4,5]);
    /// assert_eq!(s.len(), 2);
    /// ```
    #[inline]
    fn len(&self) -> usize {
        self.data.len() / self.chunk_size
    }
}

impl<'a, S, N> Push<<S as UniChunkable<N>>::Chunk> for UniChunked<S, U<N>>
where
    N: Unsigned,
    S: Set + UniChunkable<N> + PushChunk<N>,
{
    /// Push a grouped element onto the `UniChunked` type. The pushed element must
    /// have exactly `N` sub-elements.
    ///
    /// # Example
    ///
    /// ```rust
    /// use flatk::*;
    /// let mut s = UniChunked::<_, U3>::from_flat(vec![1,2,3]);
    /// s.push([4,5,6]);
    /// let mut iter = s.iter();
    /// assert_eq!(Some(&[1,2,3]), iter.next());
    /// assert_eq!(Some(&[4,5,6]), iter.next());
    /// assert_eq!(None, iter.next());
    /// ```
    #[inline]
    fn push(&mut self, element: S::Chunk) {
        self.data.push_chunk(element);
    }
}

impl<S> Push<&[<S as Set>::Elem]> for ChunkedN<S>
where
    S: Set + Push<<S as Set>::Elem>,
    <S as Set>::Elem: Clone,
{
    /// Push a grouped element onto the `ChunkedN` type.
    ///
    /// # Example
    ///
    /// ```rust
    /// use flatk::*;
    /// let mut s = ChunkedN::from_flat_with_stride(3, vec![1,2,3]);
    /// s.push(&[4,5,6]);
    /// let mut iter = s.iter();
    /// assert_eq!(Some(&[1,2,3][..]), iter.next());
    /// assert_eq!(Some(&[4,5,6][..]), iter.next());
    /// assert_eq!(None, iter.next());
    /// ```
    #[inline]
    fn push(&mut self, element: &[<S as Set>::Elem]) {
        for e in element {
            self.data.push(e.clone());
        }
    }
}

impl<S, N> ExtendFromSlice for UniChunked<S, U<N>>
where
    S: Set + ExtendFromSlice<Item = <S as Set>::Elem>,
    N: Unsigned + Array<<S as Set>::Elem>,
    <S as Set>::Elem: bytemuck::Pod,
{
    type Item = N::Array;
    fn extend_from_slice(&mut self, other: &[Self::Item]) {
        self.data.extend_from_slice(bytemuck::cast_slice(other));
    }
}

impl<S, N> IntoIterator for UniChunked<S, U<N>>
where
    S: Set + IntoStaticChunkIterator<N>,
    N: Unsigned,
{
    type Item = <S as IntoStaticChunkIterator<N>>::Item;
    type IntoIter = <S as IntoStaticChunkIterator<N>>::IterType;

    /// Convert a `UniChunked` collection into an iterator over grouped elements.
    ///
    /// # Example
    ///
    /// ```rust
    /// use flatk::*;
    /// let mut s = UniChunked::<_, U3>::from_flat(vec![1,2,3,4,5,6]);
    /// let mut iter = s.into_iter();
    /// assert_eq!(Some([1,2,3]), iter.next());
    /// assert_eq!(Some([4,5,6]), iter.next());
    /// assert_eq!(None, iter.next());
    /// ```
    #[inline]
    fn into_iter(self) -> Self::IntoIter {
        self.data.into_static_chunk_iter()
    }
}

impl<S> IntoIterator for ChunkedN<S>
where
    S: Set + IntoChunkIterator,
{
    type Item = <S as IntoChunkIterator>::Item;
    type IntoIter = <S as IntoChunkIterator>::IterType;

    /// Convert a `ChunkedN` collection into an iterator over grouped elements.
    ///
    /// # Example
    ///
    /// ```rust
    /// use flatk::*;
    /// let mut s = ChunkedN::from_flat_with_stride(3, vec![1,2,3,4,5,6]);
    /// let mut iter = s.view().into_iter();
    /// assert_eq!(Some(&[1,2,3][..]), iter.next());
    /// assert_eq!(Some(&[4,5,6][..]), iter.next());
    /// assert_eq!(None, iter.next());
    /// ```
    #[inline]
    fn into_iter(self) -> Self::IntoIter {
        self.data.into_chunk_iter(self.chunk_size)
    }
}

impl<S, N> std::iter::FromIterator<S::Chunk> for UniChunked<S, U<N>>
where
    N: Unsigned + Default,
    S: Set + UniChunkable<N> + PushChunk<N> + Default,
{
    /// Construct a `UniChunked` collection from an iterator that produces
    /// chunked elements.
    ///
    /// # Example
    ///
    /// ```rust
    /// use flatk::*;
    /// let v = vec![[1,2,3],[4,5,6]];
    /// let s: Chunked3::<Vec<usize>> = v.into_iter().collect();
    /// let mut iter = s.iter();
    /// assert_eq!(Some(&[1,2,3]), iter.next());
    /// assert_eq!(Some(&[4,5,6]), iter.next());
    /// assert_eq!(None, iter.next());
    /// ```
    #[inline]
    fn from_iter<T>(iter: T) -> Self
    where
        T: IntoIterator<Item = S::Chunk>,
    {
        let mut s: UniChunked<S, U<N>> = UniChunked::default();
        for elem in iter {
            s.data.push_chunk(elem);
        }
        s
    }
}

impl<S, N> std::iter::Extend<<Self as Set>::Elem> for UniChunked<S, U<N>>
where
    N: Unsigned,
    S: Set + UniChunkable<N> + PushChunk<N>,
{
    /// Extend a `UniChunked` collection from an iterator over set elements.
    ///
    /// # Example
    ///
    /// ```rust
    /// use flatk::*;
    ///
    /// let v = vec![[1,2,3],[4,5,6]];
    /// let mut s = Chunked3::from_array_vec(v);
    ///
    /// let more = vec![[7,8,9],[10,11,12]];
    /// s.extend(more.iter().cloned());
    /// let mut iter = s.iter();
    /// assert_eq!(Some(&[1,2,3]), iter.next());
    /// assert_eq!(Some(&[4,5,6]), iter.next());
    /// assert_eq!(Some(&[7,8,9]), iter.next());
    /// assert_eq!(Some(&[10,11,12]), iter.next());
    /// assert_eq!(None, iter.next());
    /// ```
    ///
    /// We can do this with nested chunked types, although the we would need to first convert the
    /// incoming iterator into an appropriate chunked type, in this case it is `Chunked2<[i32; 4]>`.
    ///
    /// ```
    /// use flatk::*;
    ///
    /// let v = vec![[1i32,2],[3,4],[5,6],[7,8]];
    /// let mut s = Chunked2::from_flat(Chunked2::from_array_vec(v));
    ///
    /// let more = Chunked2::from_flat(Chunked2::from_array_vec(vec![[9, 10], [11, 12]]));
    /// s.extend(more.into_iter());
    /// let mut iter = s.iter().map(|i| i.into_arrays());
    /// assert_eq!(Some(&[[1,2], [3,4]]), iter.next());
    /// assert_eq!(Some(&[[5,6], [7,8]]), iter.next());
    /// assert_eq!(Some(&[[9,10], [11,12]]), iter.next());
    /// assert_eq!(None, iter.next());
    /// ```
    ///
    /// In the wake of const-generics, this will become a whole lot more ergonomic.
    fn extend<T>(&mut self, iter: T)
    where
        T: IntoIterator<Item = <Self as Set>::Elem>,
    {
        for i in iter {
            self.data.push_chunk(i);
        }
    }
}

//impl<S, N> std::iter::Extend<N::Array> for UniChunked<S, U<N>>
//where
//    N: Unsigned + Array<<S as Set>::Elem> + Default,
//    <S as Set>::Elem: PushArrayTo<S, N>,
//    S: Set + Default + Push<<S as Set>::Elem>,
//{
//    /// Extend a `UniChunked` collection from an iterator over arrays.
//    ///
//    /// # Example
//    ///
//    /// ```rust
//    /// use flatk::*;
//    ///
//    /// let v = vec![[1,2,3],[4,5,6]];
//    /// let mut s = Chunked3::from_array_vec(v);
//    ///
//    /// let more = vec![[7,8,9],[10,11,12]];
//    /// s.extend(more.iter().cloned());
//    /// let mut iter = s.iter();
//    /// assert_eq!(Some(&[1,2,3]), iter.next());
//    /// assert_eq!(Some(&[4,5,6]), iter.next());
//    /// assert_eq!(Some(&[7,8,9]), iter.next());
//    /// assert_eq!(Some(&[10,11,12]), iter.next());
//    /// assert_eq!(None, iter.next());
//    /// ```
//    fn extend<T>(&mut self, iter: T)
//    where
//        T: IntoIterator<Item = N::Array>,
//    {
//        for i in iter {
//            self.push(i);
//        }
//    }
//}

impl<S: Set + Default, N: Unsigned + Default> Default for UniChunked<S, U<N>> {
    #[inline]
    fn default() -> Self {
        Self::from_flat(S::default())
    }
}

pub trait ReinterpretAsGrouped<N> {
    type Output;
    fn reinterpret_as_grouped(self) -> Self::Output;
}

impl<'a, S, N, M> ReinterpretAsGrouped<N> for UniChunked<S, U<M>>
where
    S: ReinterpretAsGrouped<M>,
    <S as ReinterpretAsGrouped<M>>::Output: ReinterpretAsGrouped<N>,
{
    type Output = <<S as ReinterpretAsGrouped<M>>::Output as ReinterpretAsGrouped<N>>::Output;
    #[inline]
    fn reinterpret_as_grouped(self) -> Self::Output {
        self.data.reinterpret_as_grouped().reinterpret_as_grouped()
    }
}

pub trait PushChunk<N>: UniChunkable<N> {
    /// Push a chunk with size `N`.
    fn push_chunk(&mut self, chunk: Self::Chunk);
}

pub trait PushArrayTo<S, N>
where
    S: Set,
    N: Array<<S as Set>::Elem>,
{
    /// This method tells this type how it can be pushed to a set as an array.
    fn push_to(element: N::Array, set: &mut S);
}

pub trait PushArrayToVec<N>
where
    N: Array<Self>,
    Self: Sized,
{
    /// This method tells this type how it can be pushed to a `Vec` as an array.
    fn push_to_vec(element: N::Array, set: &mut Vec<Self>);
}

impl<S: Set + Push<<S as Set>::Elem>, N: Array<<S as Set>::Elem>> PushArrayTo<S, N> for S::Elem
where
    <S as Set>::Elem: Clone,
{
    #[inline]
    fn push_to(element: N::Array, set: &mut S) {
        for i in N::iter(&element) {
            set.push(i.clone());
        }
    }
}
impl<T: Clone, N: Array<T>> PushArrayToVec<N> for T {
    #[inline]
    fn push_to_vec(element: N::Array, set: &mut Vec<T>) {
        set.extend_from_slice(N::as_slice(&element));
    }
}

impl<S: Set + ReinterpretAsGrouped<N>, N: Array<<S as Set>::Elem> + Unsigned> AsRef<[N::Array]>
    for UniChunked<S, U<N>>
where
    <S as ReinterpretAsGrouped<N>>::Output: AsRef<[N::Array]>,
    S: AsRef<[<S as Set>::Elem]>,
    <S as Set>::Elem: bytemuck::Pod,
{
    #[inline]
    fn as_ref(&self) -> &[N::Array] {
        ReinterpretAsGrouped::<N>::reinterpret_as_grouped(self.data.as_ref())
    }
}

//impl<T, N: Array<T> + Unsigned> AsRef<[N::Array]> for UniChunked<&[T], U<N>> {
//    fn as_ref(&self) -> &[N::Array] {
//        ReinterpretAsGrouped::<N>::reinterpret_as_grouped(self.data)
//    }
//}
//impl<T, N: Array<T> + Unsigned> AsRef<[N::Array]> for UniChunked<&mut [T], U<N>> {
//    fn as_ref(&self) -> &[N::Array] {
//        ReinterpretAsGrouped::<N>::reinterpret_as_grouped(&*self.data)
//    }
//}
//impl<T, N: Array<T> + Unsigned> AsMut<[N::Array]> for UniChunked<&mut [T], U<N>> {
//    fn as_mut(&mut self) -> &mut [N::Array] {
//        ReinterpretAsGrouped::<N>::reinterpret_as_grouped(&mut *self.data)
//    }
//}

impl<S, N> IntoOwned for UniChunked<S, N>
where
    S: IntoOwned,
    N: Copy,
{
    type Owned = UniChunked<<S as IntoOwned>::Owned, N>;

    /// Convert this `UniChunked` collection to an owned one.
    ///
    /// # Example
    ///
    /// ```rust
    /// use flatk::*;
    /// let v = vec![1,2,3,4,5,6];
    /// let s_view = UniChunked::<_, U3>::from_flat(v.as_slice());
    /// let s_owned = UniChunked::<_, U3>::from_flat(v.clone());
    /// assert_eq!(s_view.into_owned(), s_owned);
    /// ```
    #[inline]
    fn into_owned(self) -> Self::Owned {
        UniChunked {
            data: self.data.into_owned(),
            chunk_size: self.chunk_size,
        }
    }
}

impl<S, N> IntoOwnedData for UniChunked<S, N>
where
    S: IntoOwnedData,
    N: Copy,
{
    type OwnedData = UniChunked<S::OwnedData, N>;
    #[inline]
    fn into_owned_data(self) -> Self::OwnedData {
        let UniChunked { chunk_size, data } = self;
        UniChunked {
            chunk_size,
            data: data.into_owned_data(),
        }
    }
}

/*
 * Indexing
 */

impl<'a, S, N> GetIndex<'a, UniChunked<S, U<N>>> for usize
where
    S: Set + UniChunkable<N> + Get<'a, StaticRange<N>>,
    N: Unsigned,
{
    type Output = S::Output;

    /// Get an element of the given `UniChunked` collection.
    #[inline]
    fn get(self, chunked: &UniChunked<S, U<N>>) -> Option<Self::Output> {
        if self < chunked.len() {
            chunked.data.get(StaticRange::new(self * N::to_usize()))
        } else {
            None
        }
    }
}

impl<'a, S, N> GetIndex<'a, UniChunked<S, U<N>>> for &usize
where
    S: Set + UniChunkable<N> + Get<'a, StaticRange<N>>,
    N: Unsigned,
{
    type Output = S::Output;

    /// Get an element of the given `UniChunked` collection.
    #[inline]
    fn get(self, chunked: &UniChunked<S, U<N>>) -> Option<Self::Output> {
        GetIndex::get(*self, chunked)
    }
}

impl<'a, S, N> GetIndex<'a, UniChunked<S, U<N>>> for std::ops::Range<usize>
where
    S: Set + UniChunkable<N> + Get<'a, std::ops::Range<usize>>,
    N: Unsigned + Default,
{
    type Output = UniChunked<S::Output, U<N>>;

    /// Get a `[begin..end)` subview of the given `UniChunked` collection.
    #[inline]
    fn get(self, chunked: &UniChunked<S, U<N>>) -> Option<Self::Output> {
        if self.start <= self.end && self.end <= chunked.len() {
            chunked
                .data
                .get(N::to_usize() * self.start..N::to_usize() * self.end)
                .map(|data| UniChunked {
                    data,
                    chunk_size: Default::default(),
                })
        } else {
            None
        }
    }
}

impl<'a, S, N, M> GetIndex<'a, UniChunked<S, U<M>>> for StaticRange<N>
where
    S: Set,
    M: Unsigned,
    N: Unsigned + std::ops::Mul<M>,
    StaticRange<<N as std::ops::Mul<M>>::Output>: GetIndex<'a, S>,
{
    type Output = UniChunked<<StaticRange<N::Output> as GetIndex<'a, S>>::Output, U<M>>;

    /// Get a statically sized subview of the given `UniChunked` collection.
    #[inline]
    fn get(self, chunked: &UniChunked<S, U<M>>) -> Option<Self::Output> {
        let rng = StaticRange::<N::Output>::new(self.start * M::to_usize());
        let UniChunked { data, chunk_size } = chunked;
        GetIndex::get(rng, data).map(|data| UniChunked {
            data,
            chunk_size: *chunk_size,
        })
    }
}

impl<'a, S> GetIndex<'a, ChunkedN<S>> for usize
where
    S: Set + Get<'a, std::ops::Range<usize>>,
{
    type Output = S::Output;

    /// Get an element of the given `ChunkedN` collection.
    #[inline]
    fn get(self, chunked: &ChunkedN<S>) -> Option<Self::Output> {
        if self < chunked.len() {
            let stride = chunked.chunk_size;
            chunked.data.get(std::ops::Range {
                start: self * stride,
                end: (self + 1) * stride,
            })
        } else {
            None
        }
    }
}

impl<'a, S> GetIndex<'a, ChunkedN<S>> for std::ops::Range<usize>
where
    S: Set + Get<'a, std::ops::Range<usize>>,
{
    type Output = ChunkedN<S::Output>;

    /// Get a `[begin..end)` subview of the given `ChunkedN` collection.
    #[inline]
    fn get(self, chunked: &ChunkedN<S>) -> Option<Self::Output> {
        if self.start <= self.end && self.end <= chunked.len() {
            let stride = chunked.chunk_size;
            chunked
                .data
                .get(stride * self.start..stride * self.end)
                .map(|data| UniChunked {
                    data,
                    chunk_size: stride,
                })
        } else {
            None
        }
    }
}

impl<S, N> IsolateIndex<UniChunked<S, U<N>>> for usize
where
    S: Set + Isolate<StaticRange<N>>,
    N: Unsigned,
{
    type Output = S::Output;
    #[inline]
    unsafe fn isolate_unchecked(self, chunked: UniChunked<S, U<N>>) -> Self::Output {
        chunked
            .data
            .isolate_unchecked(StaticRange::new(self * N::to_usize()))
    }

    /// Isolate a chunk of the given `UniChunked` collection.
    #[inline]
    fn try_isolate(self, chunked: UniChunked<S, U<N>>) -> Option<Self::Output> {
        if self * N::to_usize() < chunked.data.len() {
            chunked
                .data
                .try_isolate(StaticRange::new(self * N::to_usize()))
        } else {
            None
        }
    }
}

impl<S, N> IsolateIndex<UniChunked<S, U<N>>> for std::ops::Range<usize>
where
    S: Set + Isolate<std::ops::Range<usize>>,
    N: Unsigned + Default,
{
    type Output = UniChunked<S::Output, U<N>>;

    #[inline]
    unsafe fn isolate_unchecked(self, chunked: UniChunked<S, U<N>>) -> Self::Output {
        UniChunked {
            data: chunked
                .data
                .isolate_unchecked(N::to_usize() * self.start..self.end * N::to_usize()),
            chunk_size: Default::default(),
        }
    }
    /// Isolate a `[begin..end)` range of the given `UniChunked` collection.
    #[inline]
    fn try_isolate(self, chunked: UniChunked<S, U<N>>) -> Option<Self::Output> {
        let data_end = self.end * N::to_usize();
        if self.start <= self.end && data_end <= chunked.data.len() {
            chunked
                .data
                .try_isolate(N::to_usize() * self.start..data_end)
                .map(|data| UniChunked {
                    data,
                    chunk_size: Default::default(),
                })
        } else {
            None
        }
    }
}

impl<S, N, M> IsolateIndex<UniChunked<S, U<M>>> for StaticRange<N>
where
    S: Set,
    M: Unsigned,
    N: Unsigned + std::ops::Mul<M>,
    StaticRange<<N as std::ops::Mul<M>>::Output>: IsolateIndex<S>,
{
    type Output = UniChunked<<StaticRange<N::Output> as IsolateIndex<S>>::Output, U<M>>;

    #[inline]
    unsafe fn isolate_unchecked(self, set: UniChunked<S, U<M>>) -> Self::Output {
        let rng = StaticRange::<N::Output>::new(self.start * M::to_usize());
        let UniChunked { data, chunk_size } = set;
        UniChunked {
            data: IsolateIndex::isolate_unchecked(rng, data),
            chunk_size,
        }
    }
    #[inline]
    fn try_isolate(self, set: UniChunked<S, U<M>>) -> Option<Self::Output> {
        let rng = StaticRange::<N::Output>::new(self.start * M::to_usize());
        let UniChunked { data, chunk_size } = set;
        IsolateIndex::try_isolate(rng, data).map(|data| UniChunked { data, chunk_size })
    }
}

impl<S> IsolateIndex<ChunkedN<S>> for usize
where
    S: Set + Isolate<std::ops::Range<usize>>,
{
    type Output = S::Output;

    #[inline]
    unsafe fn isolate_unchecked(self, chunked: ChunkedN<S>) -> Self::Output {
        let stride = chunked.chunk_size;
        chunked.data.isolate_unchecked(std::ops::Range {
            start: self * stride,
            end: (self + 1) * stride,
        })
    }
    /// Isolate a chunk of the given `ChunkedN` collection.
    #[inline]
    fn try_isolate(self, chunked: ChunkedN<S>) -> Option<Self::Output> {
        if self < chunked.len() {
            let stride = chunked.chunk_size;
            chunked.data.try_isolate(std::ops::Range {
                start: self * stride,
                end: (self + 1) * stride,
            })
        } else {
            None
        }
    }
}

impl<S> IsolateIndex<ChunkedN<S>> for std::ops::Range<usize>
where
    S: Set + Isolate<std::ops::Range<usize>>,
{
    type Output = ChunkedN<S::Output>;

    #[inline]
    unsafe fn isolate_unchecked(self, chunked: ChunkedN<S>) -> Self::Output {
        let stride = chunked.chunk_size;
        UniChunked {
            data: chunked
                .data
                .isolate_unchecked(stride * self.start..stride * self.end),
            chunk_size: stride,
        }
    }
    /// Isolate a `[begin..end)` range of the given `ChunkedN` collection.
    #[inline]
    fn try_isolate(self, chunked: ChunkedN<S>) -> Option<Self::Output> {
        if self.start <= self.end && self.end <= chunked.len() {
            let stride = chunked.chunk_size;
            chunked
                .data
                .try_isolate(stride * self.start..stride * self.end)
                .map(|data| UniChunked {
                    data,
                    chunk_size: stride,
                })
        } else {
            None
        }
    }
}

//impl_isolate_index_for_static_range!(impl<S> for ChunkedN<S>);

/*
 * Indexing for statically sized UniChunked types
 */

impl<T, N> std::ops::Index<usize> for UniChunked<Vec<T>, U<N>>
where
    N: Unsigned + Array<T>,
    T: bytemuck::Pod,
{
    type Output = N::Array;

    /// Index the `UniChunked` `Vec` by `usize`.
    ///
    /// Note that this works for chunked collections that are themselves not chunked, since the
    /// item at the index of a doubly chunked collection is itself chunked, which cannot be
    /// represented by a single borrow. For more complex indexing use the `get` method provided by
    /// the `Get` trait.
    ///
    /// # Example
    ///
    /// ```rust
    /// use flatk::*;
    /// let s = Chunked3::from_flat(vec![1,2,3,4,5,6,7,8,9,10,11,12,13,14,15]);
    /// assert_eq!([7,8,9], s[2]);
    /// ```
    #[inline]
    fn index(&self, idx: usize) -> &Self::Output {
        ReinterpretAsGrouped::<N>::reinterpret_as_grouped(&self.data).index(idx)
    }
}

impl<T, N> std::ops::Index<usize> for UniChunked<&[T], U<N>>
where
    N: Unsigned + Array<T>,
    T: bytemuck::Pod,
{
    type Output = N::Array;

    /// Immutably index the `UniChunked` borrowed slice by `usize`.
    ///
    /// Note that this works for chunked collections that are themselves not chunked, since the
    /// item at the index of a doubly chunked collection is itself chunked, which cannot be
    /// represented by a single borrow. For more complex indexing use the `get` method provided by
    /// the `Get` trait.
    ///
    /// # Example
    ///
    /// ```rust
    /// use flatk::*;
    /// let s = Chunked3::from_flat(vec![1,2,3,4,5,6,7,8,9,10,11,12,13,14,15]);
    /// assert_eq!([7,8,9], s.view()[2]);
    /// ```
    #[inline]
    fn index(&self, idx: usize) -> &Self::Output {
        ReinterpretAsGrouped::<N>::reinterpret_as_grouped(self.data).index(idx)
    }
}

impl<T, N> std::ops::Index<usize> for UniChunked<&mut [T], U<N>>
where
    N: Unsigned + Array<T>,
    T: bytemuck::Pod,
{
    type Output = N::Array;

    /// Immutably index the `UniChunked` mutably borrowed slice by `usize`.
    ///
    /// Note that this works for chunked collections that are themselves not chunked, since the
    /// item at the index of a doubly chunked collection is itself chunked, which cannot be
    /// represented by a single borrow. For more complex indexing use the `get` method provided by
    /// the `Get` trait.
    ///
    /// # Example
    ///
    /// ```rust
    /// use flatk::*;
    /// let mut s = Chunked3::from_flat(vec![1,2,3,4,5,6,7,8,9,10,11,12,13,14,15]);
    /// assert_eq!([7,8,9], s.view_mut()[2]);
    /// ```
    #[inline]
    fn index(&self, idx: usize) -> &Self::Output {
        ReinterpretAsGrouped::<N>::reinterpret_as_grouped(&*self.data).index(idx)
    }
}

impl<T, N> std::ops::IndexMut<usize> for UniChunked<Vec<T>, U<N>>
where
    N: Unsigned + Array<T>,
    T: bytemuck::Pod,
{
    /// Mutably index the `UniChunked` `Vec` by `usize`.
    ///
    /// Note that this works for chunked collections that are themselves not chunked, since the
    /// item at the index of a doubly chunked collection is itself chunked, which cannot be
    /// represented by a single borrow. For more complex indexing use the `get` method provided by
    /// the `Get` trait.
    ///
    /// # Example
    ///
    /// ```rust
    /// use flatk::*;
    /// let v = vec![1,2,3,4,5,6,0,0,0,10,11,12];
    /// let mut s = Chunked3::from_flat(v);
    /// s[2] = [7,8,9];
    /// assert_eq!(vec![1,2,3,4,5,6,7,8,9,10,11,12], s.into_storage().to_vec());
    /// ```
    #[inline]
    fn index_mut(&mut self, idx: usize) -> &mut Self::Output {
        ReinterpretAsGrouped::<N>::reinterpret_as_grouped(&mut self.data).index_mut(idx)
    }
}

impl<T, N> std::ops::IndexMut<usize> for UniChunked<&mut [T], U<N>>
where
    N: Unsigned + Array<T>,
    T: bytemuck::Pod,
{
    /// Mutably index the `UniChunked` mutably borrowed slice by `usize`.
    ///
    /// Note that this works for chunked collections that are themselves not
    /// chunked, since the item at the index of a doubly chunked collection is
    /// itself chunked, which cannot be represented by a single borrow. For more
    /// complex indexing use the `get` method provided by the `Get` trait.
    ///
    /// # Example
    ///
    /// ```rust
    /// use flatk::*;
    /// let mut v = vec![1,2,3,4,5,6,0,0,0,10,11,12];
    /// let mut s = Chunked3::from_flat(v.as_mut_slice());
    /// s[2] = [7,8,9];
    /// assert_eq!(vec![1,2,3,4,5,6,7,8,9,10,11,12], v);
    /// ```
    #[inline]
    fn index_mut(&mut self, idx: usize) -> &mut Self::Output {
        ReinterpretAsGrouped::<N>::reinterpret_as_grouped(&mut *self.data).index_mut(idx)
    }
}

/*
 * Indexing for ChunkedN types.
 */

impl<T> std::ops::Index<usize> for ChunkedN<Vec<T>> {
    type Output = [T];

    /// Index the `ChunkedN` `Vec` by `usize`.
    ///
    /// Note that this works for chunked collections that are themselves not chunked, since the
    /// item at the index of a doubly chunked collection is itself chunked, which cannot be
    /// represented by a single borrow. For more complex indexing use the `get` method provided by
    /// the `Get` trait.
    ///
    /// # Example
    ///
    /// ```rust
    /// use flatk::*;
    /// let s = ChunkedN::from_flat_with_stride(3, vec![1,2,3,4,5,6,7,8,9,10,11,12,13,14,15]);
    /// assert_eq!([7,8,9], s[2]);
    /// ```
    #[inline]
    fn index(&self, idx: usize) -> &Self::Output {
        let begin = self.chunk_size * idx;
        self.data.index(begin..begin + self.chunk_size)
    }
}

impl<T> std::ops::Index<usize> for ChunkedN<&[T]> {
    type Output = [T];

    /// Immutably index the `ChunkedN` borrowed slice by `usize`.
    ///
    /// Note that this works for chunked collections that are themselves not chunked, since the
    /// item at the index of a doubly chunked collection is itself chunked, which cannot be
    /// represented by a single borrow. For more complex indexing use the `get` method provided by
    /// the `Get` trait.
    ///
    /// # Example
    ///
    /// ```rust
    /// use flatk::*;
    /// let s = ChunkedN::from_flat_with_stride(3, vec![1,2,3,4,5,6,7,8,9,10,11,12,13,14,15]);
    /// assert_eq!([7,8,9], s.view()[2]);
    /// ```
    #[inline]
    fn index(&self, idx: usize) -> &Self::Output {
        let begin = self.chunk_size * idx;
        self.data.index(begin..begin + self.chunk_size)
    }
}

impl<T> std::ops::Index<usize> for ChunkedN<&mut [T]> {
    type Output = [T];

    /// Immutably index the `ChunkedN` mutably borrowed slice by `usize`.
    ///
    /// Note that this works for chunked collections that are themselves not chunked, since the
    /// item at the index of a doubly chunked collection is itself chunked, which cannot be
    /// represented by a single borrow. For more complex indexing use the `get` method provided by
    /// the `Get` trait.
    ///
    /// # Example
    ///
    /// ```rust
    /// use flatk::*;
    /// let mut s = ChunkedN::from_flat_with_stride(3, vec![1,2,3,4,5,6,7,8,9,10,11,12,13,14,15]);
    /// assert_eq!([7,8,9], s.view_mut()[2]);
    /// ```
    #[inline]
    fn index(&self, idx: usize) -> &Self::Output {
        let begin = self.chunk_size * idx;
        self.data.index(begin..begin + self.chunk_size)
    }
}

impl<T> std::ops::IndexMut<usize> for ChunkedN<Vec<T>> {
    /// Mutably index the `ChunkedN` `Vec` by `usize`.
    ///
    /// Note that this works for chunked collections that are themselves not chunked, since the
    /// item at the index of a doubly chunked collection is itself chunked, which cannot be
    /// represented by a single borrow. For more complex indexing use the `get` method provided by
    /// the `Get` trait.
    ///
    /// # Example
    ///
    /// ```rust
    /// use flatk::*;
    /// let v = vec![1,2,3,4,5,6,0,0,0,10,11,12];
    /// let mut s = ChunkedN::from_flat_with_stride(3, v);
    /// s[2].copy_from_slice(&[7,8,9]);
    /// assert_eq!(vec![1,2,3,4,5,6,7,8,9,10,11,12], s.into_storage().to_vec());
    /// ```
    #[inline]
    fn index_mut(&mut self, idx: usize) -> &mut Self::Output {
        let begin = self.chunk_size * idx;
        self.data.index_mut(begin..begin + self.chunk_size)
    }
}

impl<T> std::ops::IndexMut<usize> for ChunkedN<&mut [T]> {
    /// Mutably index the `ChunkedN` mutably borrowed slice by `usize`.
    ///
    /// Note that this works for chunked collections that are themselves not
    /// chunked, since the item at the index of a doubly chunked collection is
    /// itself chunked, which cannot be represented by a single borrow. For more
    /// complex indexing use the `get` method provided by the `Get` trait.
    ///
    /// # Example
    ///
    /// ```rust
    /// use flatk::*;
    /// let mut v = vec![1,2,3,4,5,6,0,0,0,10,11,12];
    /// let mut s = ChunkedN::from_flat_with_stride(3, v.as_mut_slice());
    /// s[2].copy_from_slice(&[7,8,9]);
    /// assert_eq!(vec![1,2,3,4,5,6,7,8,9,10,11,12], v);
    /// ```
    #[inline]
    fn index_mut(&mut self, idx: usize) -> &mut Self::Output {
        let begin = self.chunk_size * idx;
        self.data.index_mut(begin..begin + self.chunk_size)
    }
}

/*
 * Iteration
 */

impl<S, N> UniChunked<S, U<N>>
where
    N: Unsigned,
{
    /// Produces an iterator over borrowed grouped elements of `UniChunked`.
    ///
    /// # Examples
    ///
    /// The following is a simple test for iterating over a uniformly organized `Vec`.
    ///
    /// ```rust
    /// use flatk::*;
    /// let mut s = UniChunked::<_, U2>::from_flat(vec![1,2,3,4]);
    /// let mut iter = s.iter();
    /// assert_eq!(Some(&[1,2]), iter.next());
    /// assert_eq!(Some(&[3,4]), iter.next());
    /// assert_eq!(None, iter.next());
    /// ```
    ///
    /// A more complex example consists of data organized as a nested `UniChunked`.
    ///
    /// ```rust
    /// use flatk::*;
    /// let s0 = UniChunked::<_, U2>::from_flat(vec![1,2, 3,4, 5,6, 7,8, 9,10, 11,12]);
    /// let s1 = UniChunked::<_, U3>::from_flat(s0);
    /// let mut iter1 = s1.iter();
    /// let mut s0 = iter1.next().unwrap();
    /// let mut iter0 = s0.iter();
    /// assert_eq!(Some(&[1,2]), iter0.next());
    /// assert_eq!(Some(&[3,4]), iter0.next());
    /// assert_eq!(Some(&[5,6]), iter0.next());
    /// assert_eq!(None, iter0.next());
    /// let s0 = iter1.next().unwrap();
    /// let mut iter0 = s0.iter();
    /// assert_eq!(Some(&[7,8]), iter0.next());
    /// assert_eq!(Some(&[9,10]), iter0.next());
    /// assert_eq!(Some(&[11,12]), iter0.next());
    /// assert_eq!(None, iter0.next());
    /// ```
    #[inline]
    pub fn iter<'a>(&'a self) -> <S::Type as IntoStaticChunkIterator<N>>::IterType
    where
        S: View<'a>,
        <S as View<'a>>::Type: IntoStaticChunkIterator<N>,
    {
        self.data.view().into_static_chunk_iter()
    }

    /// Produces an iterator over mutably borrowed grouped elements of `UniChunked`.
    ///
    /// # Examples
    ///
    /// The following example shows a simple modification of a uniformly organized `Vec`.
    ///
    /// ```rust
    /// use flatk::*;
    /// let mut s = UniChunked::<_, U2>::from_flat(vec![0,1,2,3]);
    /// for i in s.iter_mut() {
    ///     i[0] += 1;
    ///     i[1] += 1;
    /// }
    /// let mut iter = s.iter();
    /// assert_eq!(Some(&[1,2]), iter.next());
    /// assert_eq!(Some(&[3,4]), iter.next());
    /// assert_eq!(None, iter.next());
    /// ```
    ///
    /// Nested `UniChunked`s can also be modified as follows:
    ///
    /// ```rust
    /// use flatk::*;
    /// let mut s0 = UniChunked::<_, U2>::from_flat(vec![1,2, 3,4, 5,6, 7,8, 9,10, 11,12]);
    /// let mut s1 = UniChunked::<_, U3>::from_flat(s0);
    /// for mut i in s1.iter_mut() {
    ///     for j in i.iter_mut() {
    ///         j[0] += 1;
    ///         j[1] += 2;
    ///     }
    /// }
    /// let mut iter1 = s1.iter();
    /// let s0 = iter1.next().unwrap();
    /// let mut iter0 = s0.iter();
    /// assert_eq!(Some(&[2,4]), iter0.next());
    /// assert_eq!(Some(&[4,6]), iter0.next());
    /// assert_eq!(Some(&[6,8]), iter0.next());
    /// assert_eq!(None, iter0.next());
    /// let s0 = iter1.next().unwrap();
    /// let mut iter0 = s0.iter();
    /// assert_eq!(Some(&[8,10]), iter0.next());
    /// assert_eq!(Some(&[10,12]), iter0.next());
    /// assert_eq!(Some(&[12,14]), iter0.next());
    /// assert_eq!(None, iter0.next());
    /// ```
    #[inline]
    pub fn iter_mut<'a>(&'a mut self) -> <S::Type as IntoStaticChunkIterator<N>>::IterType
    where
        S: ViewMut<'a>,
        <S as ViewMut<'a>>::Type: IntoStaticChunkIterator<N>,
    {
        self.data.view_mut().into_static_chunk_iter()
    }
}

impl<'a, S, N> ViewIterator<'a> for UniChunked<S, U<N>>
where
    S: View<'a>,
    <S as View<'a>>::Type: IntoStaticChunkIterator<N>,
    N: Unsigned,
{
    type Item = <S::Type as IntoStaticChunkIterator<N>>::Item;
    type Iter = <S::Type as IntoStaticChunkIterator<N>>::IterType;

    #[inline]
    fn view_iter(&'a self) -> Self::Iter {
        self.iter()
    }
}

impl<'a, S, N> ViewMutIterator<'a> for UniChunked<S, U<N>>
where
    S: ViewMut<'a>,
    <S as ViewMut<'a>>::Type: IntoStaticChunkIterator<N>,
    N: Unsigned,
{
    type Item = <S::Type as IntoStaticChunkIterator<N>>::Item;
    type Iter = <S::Type as IntoStaticChunkIterator<N>>::IterType;

    #[inline]
    fn view_mut_iter(&'a mut self) -> Self::Iter {
        self.iter_mut()
    }
}

impl_atom_iterators_recursive!(impl<S, N> for UniChunked<S, N> { data });

/// A generic version of the `Chunks` iterator used by slices. This is used by
/// uniformly (but not statically) chunked collections.
pub struct Chunks<S> {
    chunk_size: usize,
    data: S,
}

impl<S> Iterator for Chunks<S>
where
    S: SplitAt + Set + Dummy,
{
    type Item = S;

    #[inline]
    fn next(&mut self) -> Option<Self::Item> {
        let data_slice = std::mem::replace(&mut self.data, unsafe { Dummy::dummy() });
        if data_slice.is_empty() {
            None
        } else {
            let n = std::cmp::min(data_slice.len(), self.chunk_size);
            let (l, r) = data_slice.split_at(n);
            self.data = r;
            Some(l)
        }
    }
}

impl<S> ChunkedN<S> {
    #[inline]
    pub fn iter<'a>(&'a self) -> Chunks<S::Type>
    where
        S: View<'a>,
    {
        let UniChunked { chunk_size, data } = self;
        Chunks {
            chunk_size: *chunk_size,
            data: data.view(),
        }
    }

    /// Mutably iterate over `Chunked` data.
    ///
    /// # Example
    ///
    /// ```rust
    /// use flatk::*;
    /// let mut s = ChunkedN::from_flat_with_stride(3, vec![1,2,3,4,5,6]);
    /// s.view_mut().isolate(1).copy_from_slice(&[0; 3]);
    /// let mut iter = s.iter();
    /// assert_eq!(Some(&[1,2,3][..]), iter.next());
    /// assert_eq!(Some(&[0,0,0][..]), iter.next());
    /// assert_eq!(None, iter.next());
    /// ```
    #[inline]
    pub fn iter_mut<'a>(&'a mut self) -> Chunks<S::Type>
    where
        S: ViewMut<'a>,
    {
        let UniChunked { chunk_size, data } = self;
        Chunks {
            chunk_size: *chunk_size,
            data: data.view_mut(),
        }
    }
}

/*
 * View implementations.
 */

impl<'a, S, N> View<'a> for UniChunked<S, N>
where
    S: View<'a>,
    N: Copy,
{
    type Type = UniChunked<<S as View<'a>>::Type, N>;

    /// Create a `UniChunked` contiguous immutable (shareable) view into the
    /// underlying collection.
    ///
    /// # Example
    ///
    /// ```rust
    /// use flatk::*;
    /// let s = UniChunked::<_, U2>::from_flat(vec![0,1,2,3]);
    /// let v1 = s.view(); // s is now inaccessible.
    /// let v2 = v1.clone();
    /// let mut view1_iter = v1.iter();
    /// assert_eq!(Some(&[0,1]), view1_iter.next());
    /// assert_eq!(Some(&[2,3]), view1_iter.next());
    /// assert_eq!(None, view1_iter.next());
    /// for ((a, b), c) in v1.iter().zip(v2.iter()).zip(s.iter()) {
    ///     assert_eq!(a,b);
    ///     assert_eq!(b,c);
    /// }
    /// ```
    #[inline]
    fn view(&'a self) -> Self::Type {
        UniChunked::view(self)
    }
}

impl<'a, S, N> ViewMut<'a> for UniChunked<S, N>
where
    S: ViewMut<'a>,
    N: Copy,
{
    type Type = UniChunked<<S as ViewMut<'a>>::Type, N>;

    /// Create a `UniChunked` contiguous mutable (unique) view into the
    /// underlying collection.
    ///
    /// # Example
    ///
    /// ```rust
    /// use flatk::*;
    /// let mut s = Chunked2::from_flat(vec![0,1,2,3]);
    /// let mut v = s.view_mut();
    /// {
    ///    v.iter_mut().next().unwrap()[0] = 100;
    /// }
    /// let mut view_iter = v.iter();
    /// assert_eq!(Some(&[100,1]), view_iter.next());
    /// assert_eq!(Some(&[2,3]), view_iter.next());
    /// assert_eq!(None, view_iter.next());
    /// ```
    #[inline]
    fn view_mut(&'a mut self) -> Self::Type {
        UniChunked::view_mut(self)
    }
}

impl<'a, S> ViewIterator<'a> for ChunkedN<S>
where
    S: View<'a>,
    <S as View<'a>>::Type: SplitAt + Set + Dummy,
{
    type Item = S::Type;
    type Iter = Chunks<S::Type>;

    #[inline]
    fn view_iter(&'a self) -> Self::Iter {
        self.iter()
    }
}

impl<'a, S> ViewMutIterator<'a> for ChunkedN<S>
where
    S: ViewMut<'a>,
    <S as ViewMut<'a>>::Type: SplitAt + Set + Dummy,
{
    type Item = S::Type;
    type Iter = Chunks<S::Type>;

    #[inline]
    fn view_mut_iter(&'a mut self) -> Self::Iter {
        self.iter_mut()
    }
}

impl<S: SplitAt + Set, N: Copy + Unsigned> SplitAt for UniChunked<S, U<N>> {
    /// Split the current set into two distinct sets at the given index `mid`.
    ///
    /// # Example
    ///
    /// ```rust
    /// use flatk::*;
    /// let s = Chunked2::from_flat(vec![0,1,2,3]);
    /// let (l, r) = s.split_at(1);
    /// assert_eq!(l, Chunked2::from_flat(vec![0,1]));
    /// assert_eq!(r, Chunked2::from_flat(vec![2,3]));
    /// ```
    #[inline]
    fn split_at(self, mid: usize) -> (Self, Self) {
        let UniChunked { data, chunk_size } = self;
        let (l, r) = data.split_at(mid * N::to_usize());
        (
            UniChunked {
                data: l,
                chunk_size,
            },
            UniChunked {
                data: r,
                chunk_size,
            },
        )
    }
}

impl<S: SplitAt + Set> SplitAt for ChunkedN<S> {
    /// Split the current set into two distinct sets at the given index `mid`.
    ///
    /// # Example
    ///
    /// ```rust
    /// use flatk::*;
    /// let s = ChunkedN::from_flat_with_stride(2, vec![0,1,2,3]);
    /// let (l, r) = s.split_at(1);
    /// assert_eq!(l, ChunkedN::from_flat_with_stride(2, vec![0,1]));
    /// assert_eq!(r, ChunkedN::from_flat_with_stride(2, vec![2,3]));
    /// ```
    #[inline]
    fn split_at(self, mid: usize) -> (Self, Self) {
        let UniChunked { data, chunk_size } = self;
        let (l, r) = data.split_at(mid * chunk_size);
        (
            UniChunked {
                data: l,
                chunk_size,
            },
            UniChunked {
                data: r,
                chunk_size,
            },
        )
    }
}

impl<S: SplitPrefix<N> + Set, N: Copy> SplitFirst for UniChunked<S, U<N>> {
    type First = S::Prefix;
    #[inline]
    fn split_first(self) -> Option<(Self::First, Self)> {
        let UniChunked { data, chunk_size } = self;
        data.split_prefix().map(|(prefix, rest)| {
            (
                prefix,
                UniChunked {
                    data: rest,
                    chunk_size,
                },
            )
        })
    }
}

impl<S, N, M> SplitPrefix<M> for UniChunked<S, U<N>>
where
    S: SplitPrefix<<N as std::ops::Mul<M>>::Output> + Set,
    N: Unsigned + std::ops::Mul<M> + Copy,
    M: Unsigned,
{
    type Prefix = UniChunked<S::Prefix, U<N>>;
    #[inline]
    fn split_prefix(self) -> Option<(Self::Prefix, Self)> {
        let UniChunked { data, chunk_size } = self;
        data.split_prefix().map(|(prefix, rest)| {
            (
                UniChunked {
                    data: prefix,
                    chunk_size,
                },
                UniChunked {
                    data: rest,
                    chunk_size,
                },
            )
        })
    }
}

impl<S, M: Unsigned> SplitPrefix<M> for ChunkedN<S>
where
    S: SplitAt + Set,
{
    type Prefix = ChunkedN<S>;
    #[inline]
    fn split_prefix(self) -> Option<(Self::Prefix, Self)> {
        let mid = self.chunk_size * M::to_usize();
        if mid < self.len() {
            Some(self.split_at(mid))
        } else {
            None
        }
    }
}

impl<S, M> UniChunkable<M> for ChunkedN<S> {
    type Chunk = ChunkedN<S>; // The exact size is determined at run-time
}

impl<S, N, M> UniChunkable<M> for UniChunked<S, U<N>>
where
    S: UniChunkable<<N as std::ops::Mul<M>>::Output>,
    N: std::ops::Mul<M>,
{
    type Chunk = UniChunked<S::Chunk, U<N>>;
}

impl<S, M, N> PushChunk<M> for UniChunked<S, U<N>>
where
    S: Set
        + PushChunk<<N as std::ops::Mul<M>>::Output>
        + UniChunkable<<N as std::ops::Mul<M>>::Output>,
    N: std::ops::Mul<M>,
{
    #[inline]
    fn push_chunk(&mut self, chunk: Self::Chunk) {
        self.data.push_chunk(chunk.data);
    }
}

impl<S, N, M> IntoStaticChunkIterator<N> for UniChunked<S, M>
where
    Self: Set + SplitPrefix<N> + Dummy,
    N: Unsigned,
{
    type Item = <Self as SplitPrefix<N>>::Prefix;
    type IterType = UniChunkedIter<Self, N>;

    #[inline]
    fn into_static_chunk_iter(self) -> Self::IterType {
        self.into_generic_static_chunk_iter()
    }
}

/// Generic static sized chunk iterater appropriate for any lightweight view type collection.
pub struct UniChunkedIter<S, N> {
    pub(crate) chunk_size: std::marker::PhantomData<N>,
    pub(crate) data: S,
}

impl<S, N> Iterator for UniChunkedIter<S, N>
where
    S: Set + SplitPrefix<N> + Dummy,
    N: Unsigned,
{
    type Item = S::Prefix;

    #[inline]
    fn next(&mut self) -> Option<Self::Item> {
        let data_slice = std::mem::replace(&mut self.data, unsafe { Dummy::dummy() });
        data_slice.split_prefix().map(|(prefix, rest)| {
            self.data = rest;
            prefix
        })
    }
}

pub struct ChunkedNIter<S> {
    pub(crate) chunk_size: usize,
    pub(crate) data: S,
}

impl<S> Iterator for ChunkedNIter<S>
where
    S: Set + SplitAt + Dummy,
{
    type Item = S;

    #[inline]
    fn next(&mut self) -> Option<Self::Item> {
        if self.data.is_empty() {
            return None;
        }

        let data_slice = std::mem::replace(&mut self.data, unsafe { Dummy::dummy() });
        let (l, r) = data_slice.split_at(self.chunk_size);
        self.data = r;
        Some(l)
    }
}

impl<S: Dummy, N: Default> Dummy for UniChunked<S, N> {
    #[inline]
    unsafe fn dummy() -> Self {
        UniChunked {
            data: Dummy::dummy(),
            chunk_size: N::default(),
        }
    }
}

impl<S: Truncate, N: Unsigned> Truncate for UniChunked<S, U<N>> {
    #[inline]
    fn truncate(&mut self, new_len: usize) {
        self.data.truncate(new_len * N::to_usize());
    }
}

impl<S: Truncate> Truncate for ChunkedN<S> {
    #[inline]
    fn truncate(&mut self, new_len: usize) {
        self.data.truncate(new_len * self.chunk_size);
    }
}

impl<S: IntoStorage, N> IntoStorage for UniChunked<S, N> {
    type StorageType = <S as IntoStorage>::StorageType;
    /// Strip away the uniform organization of the underlying data, and return the underlying data.
    #[inline]
    fn into_storage(self) -> Self::StorageType {
        self.data.into_storage()
    }
}
impl<T, S: CloneWithStorage<T>, N: Clone> CloneWithStorage<T> for UniChunked<S, N> {
    type CloneType = UniChunked<S::CloneType, N>;
    #[inline]
    fn clone_with_storage(&self, storage: T) -> Self::CloneType {
        UniChunked {
            chunk_size: self.chunk_size.clone(),
            data: self.data.clone_with_storage(storage),
        }
    }
}

impl<'a, S: StorageView<'a>, N> StorageView<'a> for UniChunked<S, N> {
    type StorageView = S::StorageView;
    /// Return a view to the underlying storage type.
    ///
    /// # Example
    ///
    /// ```rust
    /// use flatk::*;
    /// let v = vec![1,2,3,4,5,6,7,8,9,10,11,12];
    /// let s0 = Chunked2::from_flat(v.clone());
    /// let s1 = ChunkedN::from_flat_with_stride(3, s0.clone());
    /// assert_eq!(s1.storage_view(), v.as_slice());
    /// assert_eq!(s0.storage_view(), v.as_slice());
    /// ```
    #[inline]
    fn storage_view(&'a self) -> Self::StorageView {
        self.data.storage_view()
    }
}

impl<S: Storage, N> Storage for UniChunked<S, N> {
    type Storage = S::Storage;
    /// Return an immutable reference to the underlying storage type.
    ///
    /// # Example
    ///
    /// ```rust
    /// use flatk::*;
    /// let v = vec![1,2,3,4,5,6,7,8,9,10,11,12];
    /// let mut s0 = Chunked2::from_flat(v.clone());
    /// let s1 = ChunkedN::from_flat_with_stride(3, s0.clone());
    /// assert_eq!(s1.storage(), &v);
    /// assert_eq!(s0.storage(), &v);
    /// assert_eq!(s0.view_mut().storage(), v.as_slice());
    /// ```
    #[inline]
    fn storage(&self) -> &Self::Storage {
        self.data.storage()
    }
}

impl<S: StorageMut, N> StorageMut for UniChunked<S, N> {
    /// Return a mutable reference to the underlying storage type.
    ///
    /// # Example
    ///
    /// ```rust
    /// use flatk::*;
    /// let mut v = vec![1,2,3,4,5,6,7,8,9,10,11,12];
    /// let mut s0 = Chunked2::from_flat(v.clone());
    /// let mut s1 = ChunkedN::from_flat_with_stride(3, s0.clone());
    /// assert_eq!(s1.storage_mut(), &mut v);
    /// assert_eq!(s0.storage_mut(), &mut v);
    /// ```
    #[inline]
    fn storage_mut(&mut self) -> &mut Self::Storage {
        self.data.storage_mut()
    }
}

/// Required for building `Subset`s of `UniChunked` types.
impl<S: RemovePrefix, N: Unsigned> RemovePrefix for UniChunked<S, U<N>> {
    #[inline]
    fn remove_prefix(&mut self, n: usize) {
        self.data.remove_prefix(n * N::to_usize());
    }
}

impl<S: RemovePrefix> RemovePrefix for ChunkedN<S> {
    #[inline]
    fn remove_prefix(&mut self, n: usize) {
        self.data.remove_prefix(n * self.chunk_size);
    }
}

impl<S: Clear, N> Clear for UniChunked<S, N> {
    #[inline]
    fn clear(&mut self) {
        self.data.clear();
    }
}

/// Pass through the conversion for structure type `UniChunked`.
impl<S: StorageInto<T>, N, T> StorageInto<T> for UniChunked<S, N> {
    type Output = UniChunked<S::Output, N>;
    #[inline]
    fn storage_into(self) -> Self::Output {
        UniChunked {
            data: self.data.storage_into(),
            chunk_size: self.chunk_size,
        }
    }
}

/// Map the underlying storage type.
impl<S: MapStorage<Out>, N, Out> MapStorage<Out> for UniChunked<S, N> {
    type Input = S::Input;
    type Output = UniChunked<S::Output, N>;
    #[inline]
    fn map_storage<F: FnOnce(Self::Input) -> Out>(self, f: F) -> Self::Output {
        UniChunked {
            data: self.data.map_storage(f),
            chunk_size: self.chunk_size,
        }
    }
}

impl<S: SwapChunks> SwapChunks for ChunkedN<S> {
    #[inline]
    fn swap_chunks(&mut self, begin_a: usize, begin_b: usize, chunk_size: usize) {
        assert!(begin_a + chunk_size <= begin_b || begin_b + chunk_size <= begin_a);
        self.data.swap_chunks(
            self.chunk_size * begin_a,
            self.chunk_size * begin_b,
            self.chunk_size * chunk_size,
        );
    }
}

impl<S: SwapChunks, N: Unsigned> SwapChunks for UniChunked<S, U<N>> {
    #[inline]
    fn swap_chunks(&mut self, begin_a: usize, begin_b: usize, chunk_size: usize) {
        assert!(begin_a + chunk_size <= begin_b || begin_b + chunk_size <= begin_a);
        self.data.swap_chunks(
            N::to_usize() * begin_a,
            N::to_usize() * begin_b,
            N::to_usize() * chunk_size,
        );
    }
}

/// This is a more general implementation of permute in place that is also used for slices.
impl<S: Set + SwapChunks> PermuteInPlace for ChunkedN<S> {
    /// Permute this collection according to the given permutation.
    /// The given permutation must have length equal to this collection.
    /// The slice `seen` is provided to keep track of which elements have already been seen.
    /// `seen` is assumed to be initialized to `false` and have length equal or
    /// larger than this collection.
    fn permute_in_place(&mut self, permutation: &[usize], seen: &mut [bool]) {
        debug_assert_eq!(permutation.len(), self.len());
        debug_assert!(seen.len() >= self.len());
        debug_assert!(seen.iter().all(|&s| !s));

        // Mark all items that are already in their correct position as seen.
        seen.iter_mut()
            .enumerate()
            .zip(permutation.iter())
            .filter_map(|((i, s), &p)| if p == i { Some(s) } else { None })
            .for_each(|s| *s = true);

        for unseen_i in 0..seen.len() {
            if seen[unseen_i] {
                continue;
            }

            let mut i = unseen_i;
            loop {
                let idx = permutation[i];
                if seen[idx] {
                    break;
                }

                self.data
                    .swap_chunks(self.chunk_size * i, self.chunk_size * idx, self.chunk_size);

                seen[i] = true;
                i = idx;
            }
        }
    }
}

impl<S: Dummy, N: Unsigned + Default> PermuteInPlace for UniChunked<S, U<N>>
where
    ChunkedN<S>: PermuteInPlace,
{
    /// Permute this collection according to the given permutation.
    ///
    /// The given permutation must have length equal to this collection.
    /// The slice `seen` is provided to keep track of which elements have already been seen.
    /// `seen` is assumed to be initialized to `false` and have length equal or
    /// larger than this collection.
    #[inline]
    fn permute_in_place(&mut self, permutation: &[usize], seen: &mut [bool]) {
        let data = std::mem::replace(&mut self.data, unsafe { Dummy::dummy() });
        let mut chunked = UniChunked {
            chunk_size: N::to_usize(),
            data,
        };
        chunked.permute_in_place(permutation, seen);

        self.data = chunked.data;
    }
}

impl<T, S: CloneIntoOther<T>, N> CloneIntoOther<UniChunked<T, N>> for UniChunked<S, N> {
    #[inline]
    fn clone_into_other(&self, other: &mut UniChunked<T, N>) {
        self.data.clone_into_other(&mut other.data);
    }
}
impl<S: Reserve, N: Dimension> Reserve for UniChunked<S, N> {
    #[inline]
    fn reserve_with_storage(&mut self, n: usize, storage_n: usize) {
        self.data
            .reserve_with_storage(n * self.chunk_size(), storage_n);
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    #[test]
    fn unichunked_viewable() {
        let mut s = Chunked2::from_flat(vec![0, 1, 2, 3]);
        let mut v = (&mut s).into_view();
        {
            v.iter_mut().next().unwrap()[0] = 100;
        }
        let mut view_iter = v.iter();
        assert_eq!(Some(&[100, 1]), view_iter.next());
        assert_eq!(Some(&[2, 3]), view_iter.next());
        assert_eq!(None, view_iter.next());
    }

    #[test]
    fn unichunked_index() {
        let s = Chunked3::from_flat(vec![1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15]);
        assert_eq!([7, 8, 9], s[2]);

        let s = Chunked3::from_flat(vec![1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15]);
        assert_eq!([7, 8, 9], s.view()[2]);

        let mut s = Chunked3::from_flat(vec![1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15]);
        assert_eq!([7, 8, 9], s.view_mut()[2]);

        let v = vec![1, 2, 3, 4, 5, 6, 0, 0, 0, 10, 11, 12];
        let mut s = Chunked3::from_flat(v);
        s[2] = [7, 8, 9];
        assert_eq!(
            vec![1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12],
            s.into_storage().to_vec()
        );

        let mut v = vec![1, 2, 3, 4, 5, 6, 0, 0, 0, 10, 11, 12];
        let mut s = Chunked3::from_flat(v.as_mut_slice());
        s[2] = [7, 8, 9];
        assert_eq!(vec![1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12], v);

        let s = ChunkedN::from_flat_with_stride(
            3,
            vec![1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15],
        );
        assert_eq!([7, 8, 9], s[2]);

        let s = ChunkedN::from_flat_with_stride(
            3,
            vec![1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15],
        );
        assert_eq!([7, 8, 9], s.view()[2]);

        let mut s = ChunkedN::from_flat_with_stride(
            3,
            vec![1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15],
        );
        assert_eq!([7, 8, 9], s.view_mut()[2]);

        let v = vec![1, 2, 3, 4, 5, 6, 0, 0, 0, 10, 11, 12];
        let mut s = ChunkedN::from_flat_with_stride(3, v);
        s[2].copy_from_slice(&[7, 8, 9]);
        assert_eq!(
            vec![1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12],
            s.into_storage().to_vec()
        );

        let mut v = vec![1, 2, 3, 4, 5, 6, 0, 0, 0, 10, 11, 12];
        let mut s = ChunkedN::from_flat_with_stride(3, v.as_mut_slice());
        s[2].copy_from_slice(&[7, 8, 9]);
        assert_eq!(vec![1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12], v);
    }
}