//! Some iterator that produces tuples
use std::iter::Fuse;
use std::iter::FusedIterator;
use std::iter::Take;
use std::iter::Cycle;
use std::marker::PhantomData;
// `HomogeneousTuple` is a public facade for `TupleCollect`, allowing
// tuple-related methods to be used by clients in generic contexts, while
// hiding the implementation details of `TupleCollect`.
// See https://github.com/rust-itertools/itertools/issues/387
/// Implemented for homogeneous tuples of size up to 12.
pub trait HomogeneousTuple
: TupleCollect
{}
impl<T: TupleCollect> HomogeneousTuple for T {}
/// An iterator over a incomplete tuple.
///
/// See [`.tuples()`](crate::Itertools::tuples) and
/// [`Tuples::into_buffer()`].
#[derive(Clone, Debug)]
pub struct TupleBuffer<T>
where T: HomogeneousTuple
{
cur: usize,
buf: T::Buffer,
}
impl<T> TupleBuffer<T>
where T: HomogeneousTuple
{
fn new(buf: T::Buffer) -> Self {
TupleBuffer {
cur: 0,
buf,
}
}
}
impl<T> Iterator for TupleBuffer<T>
where T: HomogeneousTuple
{
type Item = T::Item;
fn next(&mut self) -> Option<Self::Item> {
let s = self.buf.as_mut();
if let Some(ref mut item) = s.get_mut(self.cur) {
self.cur += 1;
item.take()
} else {
None
}
}
fn size_hint(&self) -> (usize, Option<usize>) {
let buffer = &self.buf.as_ref()[self.cur..];
let len = if buffer.is_empty() {
0
} else {
buffer.iter()
.position(|x| x.is_none())
.unwrap_or_else(|| buffer.len())
};
(len, Some(len))
}
}
impl<T> ExactSizeIterator for TupleBuffer<T>
where T: HomogeneousTuple
{
}
/// An iterator that groups the items in tuples of a specific size.
///
/// See [`.tuples()`](crate::Itertools::tuples) for more information.
#[derive(Clone, Debug)]
#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
pub struct Tuples<I, T>
where I: Iterator<Item = T::Item>,
T: HomogeneousTuple
{
iter: Fuse<I>,
buf: T::Buffer,
}
/// Create a new tuples iterator.
pub fn tuples<I, T>(iter: I) -> Tuples<I, T>
where I: Iterator<Item = T::Item>,
T: HomogeneousTuple
{
Tuples {
iter: iter.fuse(),
buf: Default::default(),
}
}
impl<I, T> Iterator for Tuples<I, T>
where I: Iterator<Item = T::Item>,
T: HomogeneousTuple
{
type Item = T;
fn next(&mut self) -> Option<Self::Item> {
T::collect_from_iter(&mut self.iter, &mut self.buf)
}
}
impl<I, T> Tuples<I, T>
where I: Iterator<Item = T::Item>,
T: HomogeneousTuple
{
/// Return a buffer with the produced items that was not enough to be grouped in a tuple.
///
/// ```
/// use itertools::Itertools;
///
/// let mut iter = (0..5).tuples();
/// assert_eq!(Some((0, 1, 2)), iter.next());
/// assert_eq!(None, iter.next());
/// itertools::assert_equal(vec![3, 4], iter.into_buffer());
/// ```
pub fn into_buffer(self) -> TupleBuffer<T> {
TupleBuffer::new(self.buf)
}
}
/// An iterator over all contiguous windows that produces tuples of a specific size.
///
/// See [`.tuple_windows()`](crate::Itertools::tuple_windows) for more
/// information.
#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
#[derive(Clone, Debug)]
pub struct TupleWindows<I, T>
where I: Iterator<Item = T::Item>,
T: HomogeneousTuple
{
iter: I,
last: Option<T>,
}
/// Create a new tuple windows iterator.
pub fn tuple_windows<I, T>(mut iter: I) -> TupleWindows<I, T>
where I: Iterator<Item = T::Item>,
T: HomogeneousTuple,
T::Item: Clone
{
use std::iter::once;
let mut last = None;
if T::num_items() != 1 {
// put in a duplicate item in front of the tuple; this simplifies
// .next() function.
if let Some(item) = iter.next() {
let iter = once(item.clone()).chain(once(item)).chain(&mut iter);
last = T::collect_from_iter_no_buf(iter);
}
}
TupleWindows {
iter,
last,
}
}
impl<I, T> Iterator for TupleWindows<I, T>
where I: Iterator<Item = T::Item>,
T: HomogeneousTuple + Clone,
T::Item: Clone
{
type Item = T;
fn next(&mut self) -> Option<Self::Item> {
if T::num_items() == 1 {
return T::collect_from_iter_no_buf(&mut self.iter)
}
if let Some(ref mut last) = self.last {
if let Some(new) = self.iter.next() {
last.left_shift_push(new);
return Some(last.clone());
}
}
None
}
}
impl<I, T> FusedIterator for TupleWindows<I, T>
where I: FusedIterator<Item = T::Item>,
T: HomogeneousTuple + Clone,
T::Item: Clone
{}
/// An iterator over all windows, wrapping back to the first elements when the
/// window would otherwise exceed the length of the iterator, producing tuples
/// of a specific size.
///
/// See [`.circular_tuple_windows()`](crate::Itertools::circular_tuple_windows) for more
/// information.
#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
#[derive(Debug, Clone)]
pub struct CircularTupleWindows<I, T: Clone>
where I: Iterator<Item = T::Item> + Clone,
T: TupleCollect + Clone
{
iter: Take<TupleWindows<Cycle<I>, T>>,
phantom_data: PhantomData<T>
}
pub fn circular_tuple_windows<I, T>(iter: I) -> CircularTupleWindows<I, T>
where I: Iterator<Item = T::Item> + Clone + ExactSizeIterator,
T: TupleCollect + Clone,
T::Item: Clone
{
let len = iter.len();
let iter = tuple_windows(iter.cycle()).take(len);
CircularTupleWindows {
iter,
phantom_data: PhantomData{}
}
}
impl<I, T> Iterator for CircularTupleWindows<I, T>
where I: Iterator<Item = T::Item> + Clone,
T: TupleCollect + Clone,
T::Item: Clone
{
type Item = T;
fn next(&mut self) -> Option<Self::Item> {
self.iter.next()
}
}
pub trait TupleCollect: Sized {
type Item;
type Buffer: Default + AsRef<[Option<Self::Item>]> + AsMut<[Option<Self::Item>]>;
fn collect_from_iter<I>(iter: I, buf: &mut Self::Buffer) -> Option<Self>
where I: IntoIterator<Item = Self::Item>;
fn collect_from_iter_no_buf<I>(iter: I) -> Option<Self>
where I: IntoIterator<Item = Self::Item>;
fn num_items() -> usize;
fn left_shift_push(&mut self, item: Self::Item);
}
macro_rules! count_ident{
() => {0};
($i0:ident, $($i:ident,)*) => {1 + count_ident!($($i,)*)};
}
macro_rules! rev_for_each_ident{
($m:ident, ) => {};
($m:ident, $i0:ident, $($i:ident,)*) => {
rev_for_each_ident!($m, $($i,)*);
$m!($i0);
};
}
macro_rules! impl_tuple_collect {
($dummy:ident,) => {}; // stop
($dummy:ident, $($Y:ident,)*) => (
impl_tuple_collect!($($Y,)*);
impl<A> TupleCollect for ($(ignore_ident!($Y, A),)*) {
type Item = A;
type Buffer = [Option<A>; count_ident!($($Y,)*) - 1];
#[allow(unused_assignments, unused_mut)]
fn collect_from_iter<I>(iter: I, buf: &mut Self::Buffer) -> Option<Self>
where I: IntoIterator<Item = A>
{
let mut iter = iter.into_iter();
$(
let mut $Y = None;
)*
loop {
$(
$Y = iter.next();
if $Y.is_none() {
break
}
)*
return Some(($($Y.unwrap()),*,))
}
let mut i = 0;
let mut s = buf.as_mut();
$(
if i < s.len() {
s[i] = $Y;
i += 1;
}
)*
return None;
}
fn collect_from_iter_no_buf<I>(iter: I) -> Option<Self>
where I: IntoIterator<Item = A>
{
let mut iter = iter.into_iter();
Some(($(
{ let $Y = iter.next()?; $Y },
)*))
}
fn num_items() -> usize {
count_ident!($($Y,)*)
}
fn left_shift_push(&mut self, mut item: A) {
use std::mem::replace;
let &mut ($(ref mut $Y),*,) = self;
macro_rules! replace_item{($i:ident) => {
item = replace($i, item);
}}
rev_for_each_ident!(replace_item, $($Y,)*);
drop(item);
}
}
)
}
impl_tuple_collect!(dummy, a, b, c, d, e, f, g, h, i, j, k, l,);
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