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Diffstat (limited to 'third_party/rust/itertools/src/lib.rs')
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diff --git a/third_party/rust/itertools/src/lib.rs b/third_party/rust/itertools/src/lib.rs new file mode 100644 index 0000000000..f91968870f --- /dev/null +++ b/third_party/rust/itertools/src/lib.rs @@ -0,0 +1,3784 @@ +#![warn(missing_docs)] +#![crate_name="itertools"] +#![cfg_attr(not(feature = "use_std"), no_std)] + +//! Extra iterator adaptors, functions and macros. +//! +//! To extend [`Iterator`] with methods in this crate, import +//! the [`Itertools`] trait: +//! +//! ``` +//! use itertools::Itertools; +//! ``` +//! +//! Now, new methods like [`interleave`](Itertools::interleave) +//! are available on all iterators: +//! +//! ``` +//! use itertools::Itertools; +//! +//! let it = (1..3).interleave(vec![-1, -2]); +//! itertools::assert_equal(it, vec![1, -1, 2, -2]); +//! ``` +//! +//! Most iterator methods are also provided as functions (with the benefit +//! that they convert parameters using [`IntoIterator`]): +//! +//! ``` +//! use itertools::interleave; +//! +//! for elt in interleave(&[1, 2, 3], &[2, 3, 4]) { +//! /* loop body */ +//! } +//! ``` +//! +//! ## Crate Features +//! +//! - `use_std` +//! - Enabled by default. +//! - Disable to compile itertools using `#![no_std]`. This disables +//! any items that depend on collections (like `group_by`, `unique`, +//! `kmerge`, `join` and many more). +//! +//! ## Rust Version +//! +//! This version of itertools requires Rust 1.32 or later. +#![doc(html_root_url="https://docs.rs/itertools/0.8/")] + +#[cfg(not(feature = "use_std"))] +extern crate core as std; + +#[cfg(feature = "use_alloc")] +extern crate alloc; + +#[cfg(feature = "use_alloc")] +use alloc::{ + string::String, + vec::Vec, +}; + +pub use either::Either; + +use core::borrow::Borrow; +#[cfg(feature = "use_std")] +use std::collections::HashMap; +use std::iter::{IntoIterator, once}; +use std::cmp::Ordering; +use std::fmt; +#[cfg(feature = "use_std")] +use std::collections::HashSet; +#[cfg(feature = "use_std")] +use std::hash::Hash; +#[cfg(feature = "use_alloc")] +use std::fmt::Write; +#[cfg(feature = "use_alloc")] +type VecIntoIter<T> = alloc::vec::IntoIter<T>; +#[cfg(feature = "use_alloc")] +use std::iter::FromIterator; + +#[macro_use] +mod impl_macros; + +// for compatibility with no std and macros +#[doc(hidden)] +pub use std::iter as __std_iter; + +/// The concrete iterator types. +pub mod structs { + pub use crate::adaptors::{ + Dedup, + DedupBy, + DedupWithCount, + DedupByWithCount, + Interleave, + InterleaveShortest, + FilterMapOk, + FilterOk, + Product, + PutBack, + Batching, + MapInto, + MapOk, + Merge, + MergeBy, + TakeWhileRef, + WhileSome, + Coalesce, + TupleCombinations, + Positions, + Update, + }; + #[allow(deprecated)] + pub use crate::adaptors::{MapResults, Step}; + #[cfg(feature = "use_alloc")] + pub use crate::adaptors::MultiProduct; + #[cfg(feature = "use_alloc")] + pub use crate::combinations::Combinations; + #[cfg(feature = "use_alloc")] + pub use crate::combinations_with_replacement::CombinationsWithReplacement; + pub use crate::cons_tuples_impl::ConsTuples; + pub use crate::exactly_one_err::ExactlyOneError; + pub use crate::format::{Format, FormatWith}; + pub use crate::flatten_ok::FlattenOk; + #[cfg(feature = "use_std")] + pub use crate::grouping_map::{GroupingMap, GroupingMapBy}; + #[cfg(feature = "use_alloc")] + pub use crate::groupbylazy::{IntoChunks, Chunk, Chunks, GroupBy, Group, Groups}; + pub use crate::intersperse::{Intersperse, IntersperseWith}; + #[cfg(feature = "use_alloc")] + pub use crate::kmerge_impl::{KMerge, KMergeBy}; + pub use crate::merge_join::MergeJoinBy; + #[cfg(feature = "use_alloc")] + pub use crate::multipeek_impl::MultiPeek; + #[cfg(feature = "use_alloc")] + pub use crate::peek_nth::PeekNth; + pub use crate::pad_tail::PadUsing; + pub use crate::peeking_take_while::PeekingTakeWhile; + #[cfg(feature = "use_alloc")] + pub use crate::permutations::Permutations; + pub use crate::process_results_impl::ProcessResults; + #[cfg(feature = "use_alloc")] + pub use crate::powerset::Powerset; + #[cfg(feature = "use_alloc")] + pub use crate::put_back_n_impl::PutBackN; + #[cfg(feature = "use_alloc")] + pub use crate::rciter_impl::RcIter; + pub use crate::repeatn::RepeatN; + #[allow(deprecated)] + pub use crate::sources::{RepeatCall, Unfold, Iterate}; + #[cfg(feature = "use_alloc")] + pub use crate::tee::Tee; + pub use crate::tuple_impl::{TupleBuffer, TupleWindows, CircularTupleWindows, Tuples}; + #[cfg(feature = "use_std")] + pub use crate::duplicates_impl::{Duplicates, DuplicatesBy}; + #[cfg(feature = "use_std")] + pub use crate::unique_impl::{Unique, UniqueBy}; + pub use crate::with_position::WithPosition; + pub use crate::zip_eq_impl::ZipEq; + pub use crate::zip_longest::ZipLongest; + pub use crate::ziptuple::Zip; +} + +/// Traits helpful for using certain `Itertools` methods in generic contexts. +pub mod traits { + pub use crate::tuple_impl::HomogeneousTuple; +} + +#[allow(deprecated)] +pub use crate::structs::*; +pub use crate::concat_impl::concat; +pub use crate::cons_tuples_impl::cons_tuples; +pub use crate::diff::diff_with; +pub use crate::diff::Diff; +#[cfg(feature = "use_alloc")] +pub use crate::kmerge_impl::{kmerge_by}; +pub use crate::minmax::MinMaxResult; +pub use crate::peeking_take_while::PeekingNext; +pub use crate::process_results_impl::process_results; +pub use crate::repeatn::repeat_n; +#[allow(deprecated)] +pub use crate::sources::{repeat_call, unfold, iterate}; +pub use crate::with_position::Position; +pub use crate::unziptuple::{multiunzip, MultiUnzip}; +pub use crate::ziptuple::multizip; +mod adaptors; +mod either_or_both; +pub use crate::either_or_both::EitherOrBoth; +#[doc(hidden)] +pub mod free; +#[doc(inline)] +pub use crate::free::*; +mod concat_impl; +mod cons_tuples_impl; +#[cfg(feature = "use_alloc")] +mod combinations; +#[cfg(feature = "use_alloc")] +mod combinations_with_replacement; +mod exactly_one_err; +mod diff; +mod flatten_ok; +#[cfg(feature = "use_std")] +mod extrema_set; +mod format; +#[cfg(feature = "use_std")] +mod grouping_map; +#[cfg(feature = "use_alloc")] +mod group_map; +#[cfg(feature = "use_alloc")] +mod groupbylazy; +mod intersperse; +#[cfg(feature = "use_alloc")] +mod k_smallest; +#[cfg(feature = "use_alloc")] +mod kmerge_impl; +#[cfg(feature = "use_alloc")] +mod lazy_buffer; +mod merge_join; +mod minmax; +#[cfg(feature = "use_alloc")] +mod multipeek_impl; +mod pad_tail; +#[cfg(feature = "use_alloc")] +mod peek_nth; +mod peeking_take_while; +#[cfg(feature = "use_alloc")] +mod permutations; +#[cfg(feature = "use_alloc")] +mod powerset; +mod process_results_impl; +#[cfg(feature = "use_alloc")] +mod put_back_n_impl; +#[cfg(feature = "use_alloc")] +mod rciter_impl; +mod repeatn; +mod size_hint; +mod sources; +#[cfg(feature = "use_alloc")] +mod tee; +mod tuple_impl; +#[cfg(feature = "use_std")] +mod duplicates_impl; +#[cfg(feature = "use_std")] +mod unique_impl; +mod unziptuple; +mod with_position; +mod zip_eq_impl; +mod zip_longest; +mod ziptuple; + +#[macro_export] +/// Create an iterator over the “cartesian product” of iterators. +/// +/// Iterator element type is like `(A, B, ..., E)` if formed +/// from iterators `(I, J, ..., M)` with element types `I::Item = A`, `J::Item = B`, etc. +/// +/// ``` +/// # use itertools::iproduct; +/// # +/// # fn main() { +/// // Iterate over the coordinates of a 4 x 4 x 4 grid +/// // from (0, 0, 0), (0, 0, 1), .., (0, 1, 0), (0, 1, 1), .. etc until (3, 3, 3) +/// for (i, j, k) in iproduct!(0..4, 0..4, 0..4) { +/// // .. +/// } +/// # } +/// ``` +macro_rules! iproduct { + (@flatten $I:expr,) => ( + $I + ); + (@flatten $I:expr, $J:expr, $($K:expr,)*) => ( + $crate::iproduct!(@flatten $crate::cons_tuples($crate::iproduct!($I, $J)), $($K,)*) + ); + ($I:expr) => ( + $crate::__std_iter::IntoIterator::into_iter($I) + ); + ($I:expr, $J:expr) => ( + $crate::Itertools::cartesian_product($crate::iproduct!($I), $crate::iproduct!($J)) + ); + ($I:expr, $J:expr, $($K:expr),+) => ( + $crate::iproduct!(@flatten $crate::iproduct!($I, $J), $($K,)+) + ); +} + +#[macro_export] +/// Create an iterator running multiple iterators in lockstep. +/// +/// The `izip!` iterator yields elements until any subiterator +/// returns `None`. +/// +/// This is a version of the standard ``.zip()`` that's supporting more than +/// two iterators. The iterator element type is a tuple with one element +/// from each of the input iterators. Just like ``.zip()``, the iteration stops +/// when the shortest of the inputs reaches its end. +/// +/// **Note:** The result of this macro is in the general case an iterator +/// composed of repeated `.zip()` and a `.map()`; it has an anonymous type. +/// The special cases of one and two arguments produce the equivalent of +/// `$a.into_iter()` and `$a.into_iter().zip($b)` respectively. +/// +/// Prefer this macro `izip!()` over [`multizip`] for the performance benefits +/// of using the standard library `.zip()`. +/// +/// ``` +/// # use itertools::izip; +/// # +/// # fn main() { +/// +/// // iterate over three sequences side-by-side +/// let mut results = [0, 0, 0, 0]; +/// let inputs = [3, 7, 9, 6]; +/// +/// for (r, index, input) in izip!(&mut results, 0..10, &inputs) { +/// *r = index * 10 + input; +/// } +/// +/// assert_eq!(results, [0 + 3, 10 + 7, 29, 36]); +/// # } +/// ``` +macro_rules! izip { + // @closure creates a tuple-flattening closure for .map() call. usage: + // @closure partial_pattern => partial_tuple , rest , of , iterators + // eg. izip!( @closure ((a, b), c) => (a, b, c) , dd , ee ) + ( @closure $p:pat => $tup:expr ) => { + |$p| $tup + }; + + // The "b" identifier is a different identifier on each recursion level thanks to hygiene. + ( @closure $p:pat => ( $($tup:tt)* ) , $_iter:expr $( , $tail:expr )* ) => { + $crate::izip!(@closure ($p, b) => ( $($tup)*, b ) $( , $tail )*) + }; + + // unary + ($first:expr $(,)*) => { + $crate::__std_iter::IntoIterator::into_iter($first) + }; + + // binary + ($first:expr, $second:expr $(,)*) => { + $crate::izip!($first) + .zip($second) + }; + + // n-ary where n > 2 + ( $first:expr $( , $rest:expr )* $(,)* ) => { + $crate::izip!($first) + $( + .zip($rest) + )* + .map( + $crate::izip!(@closure a => (a) $( , $rest )*) + ) + }; +} + +#[macro_export] +/// [Chain][`chain`] zero or more iterators together into one sequence. +/// +/// The comma-separated arguments must implement [`IntoIterator`]. +/// The final argument may be followed by a trailing comma. +/// +/// [`chain`]: Iterator::chain +/// +/// # Examples +/// +/// Empty invocations of `chain!` expand to an invocation of [`std::iter::empty`]: +/// ``` +/// use std::iter; +/// use itertools::chain; +/// +/// let _: iter::Empty<()> = chain!(); +/// let _: iter::Empty<i8> = chain!(); +/// ``` +/// +/// Invocations of `chain!` with one argument expand to [`arg.into_iter()`](IntoIterator): +/// ``` +/// use std::{ops::Range, slice}; +/// use itertools::chain; +/// let _: <Range<_> as IntoIterator>::IntoIter = chain!((2..6),); // trailing comma optional! +/// let _: <&[_] as IntoIterator>::IntoIter = chain!(&[2, 3, 4]); +/// ``` +/// +/// Invocations of `chain!` with multiple arguments [`.into_iter()`](IntoIterator) each +/// argument, and then [`chain`] them together: +/// ``` +/// use std::{iter::*, ops::Range, slice}; +/// use itertools::{assert_equal, chain}; +/// +/// // e.g., this: +/// let with_macro: Chain<Chain<Once<_>, Take<Repeat<_>>>, slice::Iter<_>> = +/// chain![once(&0), repeat(&1).take(2), &[2, 3, 5],]; +/// +/// // ...is equivalent to this: +/// let with_method: Chain<Chain<Once<_>, Take<Repeat<_>>>, slice::Iter<_>> = +/// once(&0) +/// .chain(repeat(&1).take(2)) +/// .chain(&[2, 3, 5]); +/// +/// assert_equal(with_macro, with_method); +/// ``` +macro_rules! chain { + () => { + core::iter::empty() + }; + ($first:expr $(, $rest:expr )* $(,)?) => { + { + let iter = core::iter::IntoIterator::into_iter($first); + $( + let iter = + core::iter::Iterator::chain( + iter, + core::iter::IntoIterator::into_iter($rest)); + )* + iter + } + }; +} + +/// An [`Iterator`] blanket implementation that provides extra adaptors and +/// methods. +/// +/// This trait defines a number of methods. They are divided into two groups: +/// +/// * *Adaptors* take an iterator and parameter as input, and return +/// a new iterator value. These are listed first in the trait. An example +/// of an adaptor is [`.interleave()`](Itertools::interleave) +/// +/// * *Regular methods* are those that don't return iterators and instead +/// return a regular value of some other kind. +/// [`.next_tuple()`](Itertools::next_tuple) is an example and the first regular +/// method in the list. +pub trait Itertools : Iterator { + // adaptors + + /// Alternate elements from two iterators until both have run out. + /// + /// Iterator element type is `Self::Item`. + /// + /// This iterator is *fused*. + /// + /// ``` + /// use itertools::Itertools; + /// + /// let it = (1..7).interleave(vec![-1, -2]); + /// itertools::assert_equal(it, vec![1, -1, 2, -2, 3, 4, 5, 6]); + /// ``` + fn interleave<J>(self, other: J) -> Interleave<Self, J::IntoIter> + where J: IntoIterator<Item = Self::Item>, + Self: Sized + { + interleave(self, other) + } + + /// Alternate elements from two iterators until at least one of them has run + /// out. + /// + /// Iterator element type is `Self::Item`. + /// + /// ``` + /// use itertools::Itertools; + /// + /// let it = (1..7).interleave_shortest(vec![-1, -2]); + /// itertools::assert_equal(it, vec![1, -1, 2, -2, 3]); + /// ``` + fn interleave_shortest<J>(self, other: J) -> InterleaveShortest<Self, J::IntoIter> + where J: IntoIterator<Item = Self::Item>, + Self: Sized + { + adaptors::interleave_shortest(self, other.into_iter()) + } + + /// An iterator adaptor to insert a particular value + /// between each element of the adapted iterator. + /// + /// Iterator element type is `Self::Item`. + /// + /// This iterator is *fused*. + /// + /// ``` + /// use itertools::Itertools; + /// + /// itertools::assert_equal((0..3).intersperse(8), vec![0, 8, 1, 8, 2]); + /// ``` + fn intersperse(self, element: Self::Item) -> Intersperse<Self> + where Self: Sized, + Self::Item: Clone + { + intersperse::intersperse(self, element) + } + + /// An iterator adaptor to insert a particular value created by a function + /// between each element of the adapted iterator. + /// + /// Iterator element type is `Self::Item`. + /// + /// This iterator is *fused*. + /// + /// ``` + /// use itertools::Itertools; + /// + /// let mut i = 10; + /// itertools::assert_equal((0..3).intersperse_with(|| { i -= 1; i }), vec![0, 9, 1, 8, 2]); + /// assert_eq!(i, 8); + /// ``` + fn intersperse_with<F>(self, element: F) -> IntersperseWith<Self, F> + where Self: Sized, + F: FnMut() -> Self::Item + { + intersperse::intersperse_with(self, element) + } + + /// Create an iterator which iterates over both this and the specified + /// iterator simultaneously, yielding pairs of two optional elements. + /// + /// This iterator is *fused*. + /// + /// As long as neither input iterator is exhausted yet, it yields two values + /// via `EitherOrBoth::Both`. + /// + /// When the parameter iterator is exhausted, it only yields a value from the + /// `self` iterator via `EitherOrBoth::Left`. + /// + /// When the `self` iterator is exhausted, it only yields a value from the + /// parameter iterator via `EitherOrBoth::Right`. + /// + /// When both iterators return `None`, all further invocations of `.next()` + /// will return `None`. + /// + /// Iterator element type is + /// [`EitherOrBoth<Self::Item, J::Item>`](EitherOrBoth). + /// + /// ```rust + /// use itertools::EitherOrBoth::{Both, Right}; + /// use itertools::Itertools; + /// let it = (0..1).zip_longest(1..3); + /// itertools::assert_equal(it, vec![Both(0, 1), Right(2)]); + /// ``` + #[inline] + fn zip_longest<J>(self, other: J) -> ZipLongest<Self, J::IntoIter> + where J: IntoIterator, + Self: Sized + { + zip_longest::zip_longest(self, other.into_iter()) + } + + /// Create an iterator which iterates over both this and the specified + /// iterator simultaneously, yielding pairs of elements. + /// + /// **Panics** if the iterators reach an end and they are not of equal + /// lengths. + #[inline] + fn zip_eq<J>(self, other: J) -> ZipEq<Self, J::IntoIter> + where J: IntoIterator, + Self: Sized + { + zip_eq(self, other) + } + + /// A “meta iterator adaptor”. Its closure receives a reference to the + /// iterator and may pick off as many elements as it likes, to produce the + /// next iterator element. + /// + /// Iterator element type is `B`. + /// + /// ``` + /// use itertools::Itertools; + /// + /// // An adaptor that gathers elements in pairs + /// let pit = (0..4).batching(|it| { + /// match it.next() { + /// None => None, + /// Some(x) => match it.next() { + /// None => None, + /// Some(y) => Some((x, y)), + /// } + /// } + /// }); + /// + /// itertools::assert_equal(pit, vec![(0, 1), (2, 3)]); + /// ``` + /// + fn batching<B, F>(self, f: F) -> Batching<Self, F> + where F: FnMut(&mut Self) -> Option<B>, + Self: Sized + { + adaptors::batching(self, f) + } + + /// Return an *iterable* that can group iterator elements. + /// Consecutive elements that map to the same key (“runs”), are assigned + /// to the same group. + /// + /// `GroupBy` is the storage for the lazy grouping operation. + /// + /// If the groups are consumed in order, or if each group's iterator is + /// dropped without keeping it around, then `GroupBy` uses no + /// allocations. It needs allocations only if several group iterators + /// are alive at the same time. + /// + /// This type implements [`IntoIterator`] (it is **not** an iterator + /// itself), because the group iterators need to borrow from this + /// value. It should be stored in a local variable or temporary and + /// iterated. + /// + /// Iterator element type is `(K, Group)`: the group's key and the + /// group iterator. + /// + /// ``` + /// use itertools::Itertools; + /// + /// // group data into runs of larger than zero or not. + /// let data = vec![1, 3, -2, -2, 1, 0, 1, 2]; + /// // groups: |---->|------>|--------->| + /// + /// // Note: The `&` is significant here, `GroupBy` is iterable + /// // only by reference. You can also call `.into_iter()` explicitly. + /// let mut data_grouped = Vec::new(); + /// for (key, group) in &data.into_iter().group_by(|elt| *elt >= 0) { + /// data_grouped.push((key, group.collect())); + /// } + /// assert_eq!(data_grouped, vec![(true, vec![1, 3]), (false, vec![-2, -2]), (true, vec![1, 0, 1, 2])]); + /// ``` + #[cfg(feature = "use_alloc")] + fn group_by<K, F>(self, key: F) -> GroupBy<K, Self, F> + where Self: Sized, + F: FnMut(&Self::Item) -> K, + K: PartialEq, + { + groupbylazy::new(self, key) + } + + /// Return an *iterable* that can chunk the iterator. + /// + /// Yield subiterators (chunks) that each yield a fixed number elements, + /// determined by `size`. The last chunk will be shorter if there aren't + /// enough elements. + /// + /// `IntoChunks` is based on `GroupBy`: it is iterable (implements + /// `IntoIterator`, **not** `Iterator`), and it only buffers if several + /// chunk iterators are alive at the same time. + /// + /// Iterator element type is `Chunk`, each chunk's iterator. + /// + /// **Panics** if `size` is 0. + /// + /// ``` + /// use itertools::Itertools; + /// + /// let data = vec![1, 1, 2, -2, 6, 0, 3, 1]; + /// //chunk size=3 |------->|-------->|--->| + /// + /// // Note: The `&` is significant here, `IntoChunks` is iterable + /// // only by reference. You can also call `.into_iter()` explicitly. + /// for chunk in &data.into_iter().chunks(3) { + /// // Check that the sum of each chunk is 4. + /// assert_eq!(4, chunk.sum()); + /// } + /// ``` + #[cfg(feature = "use_alloc")] + fn chunks(self, size: usize) -> IntoChunks<Self> + where Self: Sized, + { + assert!(size != 0); + groupbylazy::new_chunks(self, size) + } + + /// Return an iterator over all contiguous windows producing tuples of + /// a specific size (up to 12). + /// + /// `tuple_windows` clones the iterator elements so that they can be + /// part of successive windows, this makes it most suited for iterators + /// of references and other values that are cheap to copy. + /// + /// ``` + /// use itertools::Itertools; + /// let mut v = Vec::new(); + /// + /// // pairwise iteration + /// for (a, b) in (1..5).tuple_windows() { + /// v.push((a, b)); + /// } + /// assert_eq!(v, vec![(1, 2), (2, 3), (3, 4)]); + /// + /// let mut it = (1..5).tuple_windows(); + /// assert_eq!(Some((1, 2, 3)), it.next()); + /// assert_eq!(Some((2, 3, 4)), it.next()); + /// assert_eq!(None, it.next()); + /// + /// // this requires a type hint + /// let it = (1..5).tuple_windows::<(_, _, _)>(); + /// itertools::assert_equal(it, vec![(1, 2, 3), (2, 3, 4)]); + /// + /// // you can also specify the complete type + /// use itertools::TupleWindows; + /// use std::ops::Range; + /// + /// let it: TupleWindows<Range<u32>, (u32, u32, u32)> = (1..5).tuple_windows(); + /// itertools::assert_equal(it, vec![(1, 2, 3), (2, 3, 4)]); + /// ``` + fn tuple_windows<T>(self) -> TupleWindows<Self, T> + where Self: Sized + Iterator<Item = T::Item>, + T: traits::HomogeneousTuple, + T::Item: Clone + { + tuple_impl::tuple_windows(self) + } + + /// Return 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 (up to 12). + /// + /// `circular_tuple_windows` clones the iterator elements so that they can be + /// part of successive windows, this makes it most suited for iterators + /// of references and other values that are cheap to copy. + /// + /// ``` + /// use itertools::Itertools; + /// let mut v = Vec::new(); + /// for (a, b) in (1..5).circular_tuple_windows() { + /// v.push((a, b)); + /// } + /// assert_eq!(v, vec![(1, 2), (2, 3), (3, 4), (4, 1)]); + /// + /// let mut it = (1..5).circular_tuple_windows(); + /// assert_eq!(Some((1, 2, 3)), it.next()); + /// assert_eq!(Some((2, 3, 4)), it.next()); + /// assert_eq!(Some((3, 4, 1)), it.next()); + /// assert_eq!(Some((4, 1, 2)), it.next()); + /// assert_eq!(None, it.next()); + /// + /// // this requires a type hint + /// let it = (1..5).circular_tuple_windows::<(_, _, _)>(); + /// itertools::assert_equal(it, vec![(1, 2, 3), (2, 3, 4), (3, 4, 1), (4, 1, 2)]); + /// ``` + fn circular_tuple_windows<T>(self) -> CircularTupleWindows<Self, T> + where Self: Sized + Clone + Iterator<Item = T::Item> + ExactSizeIterator, + T: tuple_impl::TupleCollect + Clone, + T::Item: Clone + { + tuple_impl::circular_tuple_windows(self) + } + /// Return an iterator that groups the items in tuples of a specific size + /// (up to 12). + /// + /// See also the method [`.next_tuple()`](Itertools::next_tuple). + /// + /// ``` + /// use itertools::Itertools; + /// let mut v = Vec::new(); + /// for (a, b) in (1..5).tuples() { + /// v.push((a, b)); + /// } + /// assert_eq!(v, vec![(1, 2), (3, 4)]); + /// + /// let mut it = (1..7).tuples(); + /// assert_eq!(Some((1, 2, 3)), it.next()); + /// assert_eq!(Some((4, 5, 6)), it.next()); + /// assert_eq!(None, it.next()); + /// + /// // this requires a type hint + /// let it = (1..7).tuples::<(_, _, _)>(); + /// itertools::assert_equal(it, vec![(1, 2, 3), (4, 5, 6)]); + /// + /// // you can also specify the complete type + /// use itertools::Tuples; + /// use std::ops::Range; + /// + /// let it: Tuples<Range<u32>, (u32, u32, u32)> = (1..7).tuples(); + /// itertools::assert_equal(it, vec![(1, 2, 3), (4, 5, 6)]); + /// ``` + /// + /// See also [`Tuples::into_buffer`]. + fn tuples<T>(self) -> Tuples<Self, T> + where Self: Sized + Iterator<Item = T::Item>, + T: traits::HomogeneousTuple + { + tuple_impl::tuples(self) + } + + /// Split into an iterator pair that both yield all elements from + /// the original iterator. + /// + /// **Note:** If the iterator is clonable, prefer using that instead + /// of using this method. Cloning is likely to be more efficient. + /// + /// Iterator element type is `Self::Item`. + /// + /// ``` + /// use itertools::Itertools; + /// let xs = vec![0, 1, 2, 3]; + /// + /// let (mut t1, t2) = xs.into_iter().tee(); + /// itertools::assert_equal(t1.next(), Some(0)); + /// itertools::assert_equal(t2, 0..4); + /// itertools::assert_equal(t1, 1..4); + /// ``` + #[cfg(feature = "use_alloc")] + fn tee(self) -> (Tee<Self>, Tee<Self>) + where Self: Sized, + Self::Item: Clone + { + tee::new(self) + } + + /// Return an iterator adaptor that steps `n` elements in the base iterator + /// for each iteration. + /// + /// The iterator steps by yielding the next element from the base iterator, + /// then skipping forward `n - 1` elements. + /// + /// Iterator element type is `Self::Item`. + /// + /// **Panics** if the step is 0. + /// + /// ``` + /// use itertools::Itertools; + /// + /// let it = (0..8).step(3); + /// itertools::assert_equal(it, vec![0, 3, 6]); + /// ``` + #[deprecated(note="Use std .step_by() instead", since="0.8.0")] + #[allow(deprecated)] + fn step(self, n: usize) -> Step<Self> + where Self: Sized + { + adaptors::step(self, n) + } + + /// Convert each item of the iterator using the [`Into`] trait. + /// + /// ```rust + /// use itertools::Itertools; + /// + /// (1i32..42i32).map_into::<f64>().collect_vec(); + /// ``` + fn map_into<R>(self) -> MapInto<Self, R> + where Self: Sized, + Self::Item: Into<R>, + { + adaptors::map_into(self) + } + + /// See [`.map_ok()`](Itertools::map_ok). + #[deprecated(note="Use .map_ok() instead", since="0.10.0")] + fn map_results<F, T, U, E>(self, f: F) -> MapOk<Self, F> + where Self: Iterator<Item = Result<T, E>> + Sized, + F: FnMut(T) -> U, + { + self.map_ok(f) + } + + /// Return an iterator adaptor that applies the provided closure + /// to every `Result::Ok` value. `Result::Err` values are + /// unchanged. + /// + /// ``` + /// use itertools::Itertools; + /// + /// let input = vec![Ok(41), Err(false), Ok(11)]; + /// let it = input.into_iter().map_ok(|i| i + 1); + /// itertools::assert_equal(it, vec![Ok(42), Err(false), Ok(12)]); + /// ``` + fn map_ok<F, T, U, E>(self, f: F) -> MapOk<Self, F> + where Self: Iterator<Item = Result<T, E>> + Sized, + F: FnMut(T) -> U, + { + adaptors::map_ok(self, f) + } + + /// Return an iterator adaptor that filters every `Result::Ok` + /// value with the provided closure. `Result::Err` values are + /// unchanged. + /// + /// ``` + /// use itertools::Itertools; + /// + /// let input = vec![Ok(22), Err(false), Ok(11)]; + /// let it = input.into_iter().filter_ok(|&i| i > 20); + /// itertools::assert_equal(it, vec![Ok(22), Err(false)]); + /// ``` + fn filter_ok<F, T, E>(self, f: F) -> FilterOk<Self, F> + where Self: Iterator<Item = Result<T, E>> + Sized, + F: FnMut(&T) -> bool, + { + adaptors::filter_ok(self, f) + } + + /// Return an iterator adaptor that filters and transforms every + /// `Result::Ok` value with the provided closure. `Result::Err` + /// values are unchanged. + /// + /// ``` + /// use itertools::Itertools; + /// + /// let input = vec![Ok(22), Err(false), Ok(11)]; + /// let it = input.into_iter().filter_map_ok(|i| if i > 20 { Some(i * 2) } else { None }); + /// itertools::assert_equal(it, vec![Ok(44), Err(false)]); + /// ``` + fn filter_map_ok<F, T, U, E>(self, f: F) -> FilterMapOk<Self, F> + where Self: Iterator<Item = Result<T, E>> + Sized, + F: FnMut(T) -> Option<U>, + { + adaptors::filter_map_ok(self, f) + } + + /// Return an iterator adaptor that flattens every `Result::Ok` value into + /// a series of `Result::Ok` values. `Result::Err` values are unchanged. + /// + /// This is useful when you have some common error type for your crate and + /// need to propagate it upwards, but the `Result::Ok` case needs to be flattened. + /// + /// ``` + /// use itertools::Itertools; + /// + /// let input = vec![Ok(0..2), Err(false), Ok(2..4)]; + /// let it = input.iter().cloned().flatten_ok(); + /// itertools::assert_equal(it.clone(), vec![Ok(0), Ok(1), Err(false), Ok(2), Ok(3)]); + /// + /// // This can also be used to propagate errors when collecting. + /// let output_result: Result<Vec<i32>, bool> = it.collect(); + /// assert_eq!(output_result, Err(false)); + /// ``` + fn flatten_ok<T, E>(self) -> FlattenOk<Self, T, E> + where Self: Iterator<Item = Result<T, E>> + Sized, + T: IntoIterator + { + flatten_ok::flatten_ok(self) + } + + /// Return an iterator adaptor that merges the two base iterators in + /// ascending order. If both base iterators are sorted (ascending), the + /// result is sorted. + /// + /// Iterator element type is `Self::Item`. + /// + /// ``` + /// use itertools::Itertools; + /// + /// let a = (0..11).step(3); + /// let b = (0..11).step(5); + /// let it = a.merge(b); + /// itertools::assert_equal(it, vec![0, 0, 3, 5, 6, 9, 10]); + /// ``` + fn merge<J>(self, other: J) -> Merge<Self, J::IntoIter> + where Self: Sized, + Self::Item: PartialOrd, + J: IntoIterator<Item = Self::Item> + { + merge(self, other) + } + + /// Return an iterator adaptor that merges the two base iterators in order. + /// This is much like [`.merge()`](Itertools::merge) but allows for a custom ordering. + /// + /// This can be especially useful for sequences of tuples. + /// + /// Iterator element type is `Self::Item`. + /// + /// ``` + /// use itertools::Itertools; + /// + /// let a = (0..).zip("bc".chars()); + /// let b = (0..).zip("ad".chars()); + /// let it = a.merge_by(b, |x, y| x.1 <= y.1); + /// itertools::assert_equal(it, vec![(0, 'a'), (0, 'b'), (1, 'c'), (1, 'd')]); + /// ``` + + fn merge_by<J, F>(self, other: J, is_first: F) -> MergeBy<Self, J::IntoIter, F> + where Self: Sized, + J: IntoIterator<Item = Self::Item>, + F: FnMut(&Self::Item, &Self::Item) -> bool + { + adaptors::merge_by_new(self, other.into_iter(), is_first) + } + + /// Create an iterator that merges items from both this and the specified + /// iterator in ascending order. + /// + /// It chooses whether to pair elements based on the `Ordering` returned by the + /// specified compare function. At any point, inspecting the tip of the + /// iterators `I` and `J` as items `i` of type `I::Item` and `j` of type + /// `J::Item` respectively, the resulting iterator will: + /// + /// - Emit `EitherOrBoth::Left(i)` when `i < j`, + /// and remove `i` from its source iterator + /// - Emit `EitherOrBoth::Right(j)` when `i > j`, + /// and remove `j` from its source iterator + /// - Emit `EitherOrBoth::Both(i, j)` when `i == j`, + /// and remove both `i` and `j` from their respective source iterators + /// + /// ``` + /// use itertools::Itertools; + /// use itertools::EitherOrBoth::{Left, Right, Both}; + /// + /// let multiples_of_2 = (0..10).step(2); + /// let multiples_of_3 = (0..10).step(3); + /// + /// itertools::assert_equal( + /// multiples_of_2.merge_join_by(multiples_of_3, |i, j| i.cmp(j)), + /// vec![Both(0, 0), Left(2), Right(3), Left(4), Both(6, 6), Left(8), Right(9)] + /// ); + /// ``` + #[inline] + fn merge_join_by<J, F>(self, other: J, cmp_fn: F) -> MergeJoinBy<Self, J::IntoIter, F> + where J: IntoIterator, + F: FnMut(&Self::Item, &J::Item) -> std::cmp::Ordering, + Self: Sized + { + merge_join_by(self, other, cmp_fn) + } + + /// Return an iterator adaptor that flattens an iterator of iterators by + /// merging them in ascending order. + /// + /// If all base iterators are sorted (ascending), the result is sorted. + /// + /// Iterator element type is `Self::Item`. + /// + /// ``` + /// use itertools::Itertools; + /// + /// let a = (0..6).step(3); + /// let b = (1..6).step(3); + /// let c = (2..6).step(3); + /// let it = vec![a, b, c].into_iter().kmerge(); + /// itertools::assert_equal(it, vec![0, 1, 2, 3, 4, 5]); + /// ``` + #[cfg(feature = "use_alloc")] + fn kmerge(self) -> KMerge<<Self::Item as IntoIterator>::IntoIter> + where Self: Sized, + Self::Item: IntoIterator, + <Self::Item as IntoIterator>::Item: PartialOrd, + { + kmerge(self) + } + + /// Return an iterator adaptor that flattens an iterator of iterators by + /// merging them according to the given closure. + /// + /// The closure `first` is called with two elements *a*, *b* and should + /// return `true` if *a* is ordered before *b*. + /// + /// If all base iterators are sorted according to `first`, the result is + /// sorted. + /// + /// Iterator element type is `Self::Item`. + /// + /// ``` + /// use itertools::Itertools; + /// + /// let a = vec![-1f64, 2., 3., -5., 6., -7.]; + /// let b = vec![0., 2., -4.]; + /// let mut it = vec![a, b].into_iter().kmerge_by(|a, b| a.abs() < b.abs()); + /// assert_eq!(it.next(), Some(0.)); + /// assert_eq!(it.last(), Some(-7.)); + /// ``` + #[cfg(feature = "use_alloc")] + fn kmerge_by<F>(self, first: F) + -> KMergeBy<<Self::Item as IntoIterator>::IntoIter, F> + where Self: Sized, + Self::Item: IntoIterator, + F: FnMut(&<Self::Item as IntoIterator>::Item, + &<Self::Item as IntoIterator>::Item) -> bool + { + kmerge_by(self, first) + } + + /// Return an iterator adaptor that iterates over the cartesian product of + /// the element sets of two iterators `self` and `J`. + /// + /// Iterator element type is `(Self::Item, J::Item)`. + /// + /// ``` + /// use itertools::Itertools; + /// + /// let it = (0..2).cartesian_product("αβ".chars()); + /// itertools::assert_equal(it, vec![(0, 'α'), (0, 'β'), (1, 'α'), (1, 'β')]); + /// ``` + fn cartesian_product<J>(self, other: J) -> Product<Self, J::IntoIter> + where Self: Sized, + Self::Item: Clone, + J: IntoIterator, + J::IntoIter: Clone + { + adaptors::cartesian_product(self, other.into_iter()) + } + + /// Return an iterator adaptor that iterates over the cartesian product of + /// all subiterators returned by meta-iterator `self`. + /// + /// All provided iterators must yield the same `Item` type. To generate + /// the product of iterators yielding multiple types, use the + /// [`iproduct`] macro instead. + /// + /// + /// The iterator element type is `Vec<T>`, where `T` is the iterator element + /// of the subiterators. + /// + /// ``` + /// use itertools::Itertools; + /// let mut multi_prod = (0..3).map(|i| (i * 2)..(i * 2 + 2)) + /// .multi_cartesian_product(); + /// assert_eq!(multi_prod.next(), Some(vec![0, 2, 4])); + /// assert_eq!(multi_prod.next(), Some(vec![0, 2, 5])); + /// assert_eq!(multi_prod.next(), Some(vec![0, 3, 4])); + /// assert_eq!(multi_prod.next(), Some(vec![0, 3, 5])); + /// assert_eq!(multi_prod.next(), Some(vec![1, 2, 4])); + /// assert_eq!(multi_prod.next(), Some(vec![1, 2, 5])); + /// assert_eq!(multi_prod.next(), Some(vec![1, 3, 4])); + /// assert_eq!(multi_prod.next(), Some(vec![1, 3, 5])); + /// assert_eq!(multi_prod.next(), None); + /// ``` + #[cfg(feature = "use_alloc")] + fn multi_cartesian_product(self) -> MultiProduct<<Self::Item as IntoIterator>::IntoIter> + where Self: Sized, + Self::Item: IntoIterator, + <Self::Item as IntoIterator>::IntoIter: Clone, + <Self::Item as IntoIterator>::Item: Clone + { + adaptors::multi_cartesian_product(self) + } + + /// Return an iterator adaptor that uses the passed-in closure to + /// optionally merge together consecutive elements. + /// + /// The closure `f` is passed two elements, `previous` and `current` and may + /// return either (1) `Ok(combined)` to merge the two values or + /// (2) `Err((previous', current'))` to indicate they can't be merged. + /// In (2), the value `previous'` is emitted by the iterator. + /// Either (1) `combined` or (2) `current'` becomes the previous value + /// when coalesce continues with the next pair of elements to merge. The + /// value that remains at the end is also emitted by the iterator. + /// + /// Iterator element type is `Self::Item`. + /// + /// This iterator is *fused*. + /// + /// ``` + /// use itertools::Itertools; + /// + /// // sum same-sign runs together + /// let data = vec![-1., -2., -3., 3., 1., 0., -1.]; + /// itertools::assert_equal(data.into_iter().coalesce(|x, y| + /// if (x >= 0.) == (y >= 0.) { + /// Ok(x + y) + /// } else { + /// Err((x, y)) + /// }), + /// vec![-6., 4., -1.]); + /// ``` + fn coalesce<F>(self, f: F) -> Coalesce<Self, F> + where Self: Sized, + F: FnMut(Self::Item, Self::Item) + -> Result<Self::Item, (Self::Item, Self::Item)> + { + adaptors::coalesce(self, f) + } + + /// Remove duplicates from sections of consecutive identical elements. + /// If the iterator is sorted, all elements will be unique. + /// + /// Iterator element type is `Self::Item`. + /// + /// This iterator is *fused*. + /// + /// ``` + /// use itertools::Itertools; + /// + /// let data = vec![1., 1., 2., 3., 3., 2., 2.]; + /// itertools::assert_equal(data.into_iter().dedup(), + /// vec![1., 2., 3., 2.]); + /// ``` + fn dedup(self) -> Dedup<Self> + where Self: Sized, + Self::Item: PartialEq, + { + adaptors::dedup(self) + } + + /// Remove duplicates from sections of consecutive identical elements, + /// determining equality using a comparison function. + /// If the iterator is sorted, all elements will be unique. + /// + /// Iterator element type is `Self::Item`. + /// + /// This iterator is *fused*. + /// + /// ``` + /// use itertools::Itertools; + /// + /// let data = vec![(0, 1.), (1, 1.), (0, 2.), (0, 3.), (1, 3.), (1, 2.), (2, 2.)]; + /// itertools::assert_equal(data.into_iter().dedup_by(|x, y| x.1 == y.1), + /// vec![(0, 1.), (0, 2.), (0, 3.), (1, 2.)]); + /// ``` + fn dedup_by<Cmp>(self, cmp: Cmp) -> DedupBy<Self, Cmp> + where Self: Sized, + Cmp: FnMut(&Self::Item, &Self::Item)->bool, + { + adaptors::dedup_by(self, cmp) + } + + /// Remove duplicates from sections of consecutive identical elements, while keeping a count of + /// how many repeated elements were present. + /// If the iterator is sorted, all elements will be unique. + /// + /// Iterator element type is `(usize, Self::Item)`. + /// + /// This iterator is *fused*. + /// + /// ``` + /// use itertools::Itertools; + /// + /// let data = vec!['a', 'a', 'b', 'c', 'c', 'b', 'b']; + /// itertools::assert_equal(data.into_iter().dedup_with_count(), + /// vec![(2, 'a'), (1, 'b'), (2, 'c'), (2, 'b')]); + /// ``` + fn dedup_with_count(self) -> DedupWithCount<Self> + where + Self: Sized, + { + adaptors::dedup_with_count(self) + } + + /// Remove duplicates from sections of consecutive identical elements, while keeping a count of + /// how many repeated elements were present. + /// This will determine equality using a comparison function. + /// If the iterator is sorted, all elements will be unique. + /// + /// Iterator element type is `(usize, Self::Item)`. + /// + /// This iterator is *fused*. + /// + /// ``` + /// use itertools::Itertools; + /// + /// let data = vec![(0, 'a'), (1, 'a'), (0, 'b'), (0, 'c'), (1, 'c'), (1, 'b'), (2, 'b')]; + /// itertools::assert_equal(data.into_iter().dedup_by_with_count(|x, y| x.1 == y.1), + /// vec![(2, (0, 'a')), (1, (0, 'b')), (2, (0, 'c')), (2, (1, 'b'))]); + /// ``` + fn dedup_by_with_count<Cmp>(self, cmp: Cmp) -> DedupByWithCount<Self, Cmp> + where + Self: Sized, + Cmp: FnMut(&Self::Item, &Self::Item) -> bool, + { + adaptors::dedup_by_with_count(self, cmp) + } + + /// Return an iterator adaptor that produces elements that appear more than once during the + /// iteration. Duplicates are detected using hash and equality. + /// + /// The iterator is stable, returning the duplicate items in the order in which they occur in + /// the adapted iterator. Each duplicate item is returned exactly once. If an item appears more + /// than twice, the second item is the item retained and the rest are discarded. + /// + /// ``` + /// use itertools::Itertools; + /// + /// let data = vec![10, 20, 30, 20, 40, 10, 50]; + /// itertools::assert_equal(data.into_iter().duplicates(), + /// vec![20, 10]); + /// ``` + #[cfg(feature = "use_std")] + fn duplicates(self) -> Duplicates<Self> + where Self: Sized, + Self::Item: Eq + Hash + { + duplicates_impl::duplicates(self) + } + + /// Return an iterator adaptor that produces elements that appear more than once during the + /// iteration. Duplicates are detected using hash and equality. + /// + /// Duplicates are detected by comparing the key they map to with the keying function `f` by + /// hash and equality. The keys are stored in a hash map in the iterator. + /// + /// The iterator is stable, returning the duplicate items in the order in which they occur in + /// the adapted iterator. Each duplicate item is returned exactly once. If an item appears more + /// than twice, the second item is the item retained and the rest are discarded. + /// + /// ``` + /// use itertools::Itertools; + /// + /// let data = vec!["a", "bb", "aa", "c", "ccc"]; + /// itertools::assert_equal(data.into_iter().duplicates_by(|s| s.len()), + /// vec!["aa", "c"]); + /// ``` + #[cfg(feature = "use_std")] + fn duplicates_by<V, F>(self, f: F) -> DuplicatesBy<Self, V, F> + where Self: Sized, + V: Eq + Hash, + F: FnMut(&Self::Item) -> V + { + duplicates_impl::duplicates_by(self, f) + } + + /// Return an iterator adaptor that filters out elements that have + /// already been produced once during the iteration. Duplicates + /// are detected using hash and equality. + /// + /// Clones of visited elements are stored in a hash set in the + /// iterator. + /// + /// The iterator is stable, returning the non-duplicate items in the order + /// in which they occur in the adapted iterator. In a set of duplicate + /// items, the first item encountered is the item retained. + /// + /// ``` + /// use itertools::Itertools; + /// + /// let data = vec![10, 20, 30, 20, 40, 10, 50]; + /// itertools::assert_equal(data.into_iter().unique(), + /// vec![10, 20, 30, 40, 50]); + /// ``` + #[cfg(feature = "use_std")] + fn unique(self) -> Unique<Self> + where Self: Sized, + Self::Item: Clone + Eq + Hash + { + unique_impl::unique(self) + } + + /// Return an iterator adaptor that filters out elements that have + /// already been produced once during the iteration. + /// + /// Duplicates are detected by comparing the key they map to + /// with the keying function `f` by hash and equality. + /// The keys are stored in a hash set in the iterator. + /// + /// The iterator is stable, returning the non-duplicate items in the order + /// in which they occur in the adapted iterator. In a set of duplicate + /// items, the first item encountered is the item retained. + /// + /// ``` + /// use itertools::Itertools; + /// + /// let data = vec!["a", "bb", "aa", "c", "ccc"]; + /// itertools::assert_equal(data.into_iter().unique_by(|s| s.len()), + /// vec!["a", "bb", "ccc"]); + /// ``` + #[cfg(feature = "use_std")] + fn unique_by<V, F>(self, f: F) -> UniqueBy<Self, V, F> + where Self: Sized, + V: Eq + Hash, + F: FnMut(&Self::Item) -> V + { + unique_impl::unique_by(self, f) + } + + /// Return an iterator adaptor that borrows from this iterator and + /// takes items while the closure `accept` returns `true`. + /// + /// This adaptor can only be used on iterators that implement `PeekingNext` + /// like `.peekable()`, `put_back` and a few other collection iterators. + /// + /// The last and rejected element (first `false`) is still available when + /// `peeking_take_while` is done. + /// + /// + /// See also [`.take_while_ref()`](Itertools::take_while_ref) + /// which is a similar adaptor. + fn peeking_take_while<F>(&mut self, accept: F) -> PeekingTakeWhile<Self, F> + where Self: Sized + PeekingNext, + F: FnMut(&Self::Item) -> bool, + { + peeking_take_while::peeking_take_while(self, accept) + } + + /// Return an iterator adaptor that borrows from a `Clone`-able iterator + /// to only pick off elements while the predicate `accept` returns `true`. + /// + /// It uses the `Clone` trait to restore the original iterator so that the + /// last and rejected element (first `false`) is still available when + /// `take_while_ref` is done. + /// + /// ``` + /// use itertools::Itertools; + /// + /// let mut hexadecimals = "0123456789abcdef".chars(); + /// + /// let decimals = hexadecimals.take_while_ref(|c| c.is_numeric()) + /// .collect::<String>(); + /// assert_eq!(decimals, "0123456789"); + /// assert_eq!(hexadecimals.next(), Some('a')); + /// + /// ``` + fn take_while_ref<F>(&mut self, accept: F) -> TakeWhileRef<Self, F> + where Self: Clone, + F: FnMut(&Self::Item) -> bool + { + adaptors::take_while_ref(self, accept) + } + + /// Return an iterator adaptor that filters `Option<A>` iterator elements + /// and produces `A`. Stops on the first `None` encountered. + /// + /// Iterator element type is `A`, the unwrapped element. + /// + /// ``` + /// use itertools::Itertools; + /// + /// // List all hexadecimal digits + /// itertools::assert_equal( + /// (0..).map(|i| std::char::from_digit(i, 16)).while_some(), + /// "0123456789abcdef".chars()); + /// + /// ``` + fn while_some<A>(self) -> WhileSome<Self> + where Self: Sized + Iterator<Item = Option<A>> + { + adaptors::while_some(self) + } + + /// Return an iterator adaptor that iterates over the combinations of the + /// elements from an iterator. + /// + /// Iterator element can be any homogeneous tuple of type `Self::Item` with + /// size up to 12. + /// + /// ``` + /// use itertools::Itertools; + /// + /// let mut v = Vec::new(); + /// for (a, b) in (1..5).tuple_combinations() { + /// v.push((a, b)); + /// } + /// assert_eq!(v, vec![(1, 2), (1, 3), (1, 4), (2, 3), (2, 4), (3, 4)]); + /// + /// let mut it = (1..5).tuple_combinations(); + /// assert_eq!(Some((1, 2, 3)), it.next()); + /// assert_eq!(Some((1, 2, 4)), it.next()); + /// assert_eq!(Some((1, 3, 4)), it.next()); + /// assert_eq!(Some((2, 3, 4)), it.next()); + /// assert_eq!(None, it.next()); + /// + /// // this requires a type hint + /// let it = (1..5).tuple_combinations::<(_, _, _)>(); + /// itertools::assert_equal(it, vec![(1, 2, 3), (1, 2, 4), (1, 3, 4), (2, 3, 4)]); + /// + /// // you can also specify the complete type + /// use itertools::TupleCombinations; + /// use std::ops::Range; + /// + /// let it: TupleCombinations<Range<u32>, (u32, u32, u32)> = (1..5).tuple_combinations(); + /// itertools::assert_equal(it, vec![(1, 2, 3), (1, 2, 4), (1, 3, 4), (2, 3, 4)]); + /// ``` + fn tuple_combinations<T>(self) -> TupleCombinations<Self, T> + where Self: Sized + Clone, + Self::Item: Clone, + T: adaptors::HasCombination<Self>, + { + adaptors::tuple_combinations(self) + } + + /// Return an iterator adaptor that iterates over the `k`-length combinations of + /// the elements from an iterator. + /// + /// Iterator element type is `Vec<Self::Item>`. The iterator produces a new Vec per iteration, + /// and clones the iterator elements. + /// + /// ``` + /// use itertools::Itertools; + /// + /// let it = (1..5).combinations(3); + /// itertools::assert_equal(it, vec![ + /// vec![1, 2, 3], + /// vec![1, 2, 4], + /// vec![1, 3, 4], + /// vec![2, 3, 4], + /// ]); + /// ``` + /// + /// Note: Combinations does not take into account the equality of the iterated values. + /// ``` + /// use itertools::Itertools; + /// + /// let it = vec![1, 2, 2].into_iter().combinations(2); + /// itertools::assert_equal(it, vec![ + /// vec![1, 2], // Note: these are the same + /// vec![1, 2], // Note: these are the same + /// vec![2, 2], + /// ]); + /// ``` + #[cfg(feature = "use_alloc")] + fn combinations(self, k: usize) -> Combinations<Self> + where Self: Sized, + Self::Item: Clone + { + combinations::combinations(self, k) + } + + /// Return an iterator that iterates over the `k`-length combinations of + /// the elements from an iterator, with replacement. + /// + /// Iterator element type is `Vec<Self::Item>`. The iterator produces a new Vec per iteration, + /// and clones the iterator elements. + /// + /// ``` + /// use itertools::Itertools; + /// + /// let it = (1..4).combinations_with_replacement(2); + /// itertools::assert_equal(it, vec![ + /// vec![1, 1], + /// vec![1, 2], + /// vec![1, 3], + /// vec![2, 2], + /// vec![2, 3], + /// vec![3, 3], + /// ]); + /// ``` + #[cfg(feature = "use_alloc")] + fn combinations_with_replacement(self, k: usize) -> CombinationsWithReplacement<Self> + where + Self: Sized, + Self::Item: Clone, + { + combinations_with_replacement::combinations_with_replacement(self, k) + } + + /// Return an iterator adaptor that iterates over all k-permutations of the + /// elements from an iterator. + /// + /// Iterator element type is `Vec<Self::Item>` with length `k`. The iterator + /// produces a new Vec per iteration, and clones the iterator elements. + /// + /// If `k` is greater than the length of the input iterator, the resultant + /// iterator adaptor will be empty. + /// + /// ``` + /// use itertools::Itertools; + /// + /// let perms = (5..8).permutations(2); + /// itertools::assert_equal(perms, vec![ + /// vec![5, 6], + /// vec![5, 7], + /// vec![6, 5], + /// vec![6, 7], + /// vec![7, 5], + /// vec![7, 6], + /// ]); + /// ``` + /// + /// Note: Permutations does not take into account the equality of the iterated values. + /// + /// ``` + /// use itertools::Itertools; + /// + /// let it = vec![2, 2].into_iter().permutations(2); + /// itertools::assert_equal(it, vec![ + /// vec![2, 2], // Note: these are the same + /// vec![2, 2], // Note: these are the same + /// ]); + /// ``` + /// + /// Note: The source iterator is collected lazily, and will not be + /// re-iterated if the permutations adaptor is completed and re-iterated. + #[cfg(feature = "use_alloc")] + fn permutations(self, k: usize) -> Permutations<Self> + where Self: Sized, + Self::Item: Clone + { + permutations::permutations(self, k) + } + + /// Return an iterator that iterates through the powerset of the elements from an + /// iterator. + /// + /// Iterator element type is `Vec<Self::Item>`. The iterator produces a new `Vec` + /// per iteration, and clones the iterator elements. + /// + /// The powerset of a set contains all subsets including the empty set and the full + /// input set. A powerset has length _2^n_ where _n_ is the length of the input + /// set. + /// + /// Each `Vec` produced by this iterator represents a subset of the elements + /// produced by the source iterator. + /// + /// ``` + /// use itertools::Itertools; + /// + /// let sets = (1..4).powerset().collect::<Vec<_>>(); + /// itertools::assert_equal(sets, vec![ + /// vec![], + /// vec![1], + /// vec![2], + /// vec![3], + /// vec![1, 2], + /// vec![1, 3], + /// vec![2, 3], + /// vec![1, 2, 3], + /// ]); + /// ``` + #[cfg(feature = "use_alloc")] + fn powerset(self) -> Powerset<Self> + where Self: Sized, + Self::Item: Clone, + { + powerset::powerset(self) + } + + /// Return an iterator adaptor that pads the sequence to a minimum length of + /// `min` by filling missing elements using a closure `f`. + /// + /// Iterator element type is `Self::Item`. + /// + /// ``` + /// use itertools::Itertools; + /// + /// let it = (0..5).pad_using(10, |i| 2*i); + /// itertools::assert_equal(it, vec![0, 1, 2, 3, 4, 10, 12, 14, 16, 18]); + /// + /// let it = (0..10).pad_using(5, |i| 2*i); + /// itertools::assert_equal(it, vec![0, 1, 2, 3, 4, 5, 6, 7, 8, 9]); + /// + /// let it = (0..5).pad_using(10, |i| 2*i).rev(); + /// itertools::assert_equal(it, vec![18, 16, 14, 12, 10, 4, 3, 2, 1, 0]); + /// ``` + fn pad_using<F>(self, min: usize, f: F) -> PadUsing<Self, F> + where Self: Sized, + F: FnMut(usize) -> Self::Item + { + pad_tail::pad_using(self, min, f) + } + + /// Return an iterator adaptor that wraps each element in a `Position` to + /// ease special-case handling of the first or last elements. + /// + /// Iterator element type is + /// [`Position<Self::Item>`](Position) + /// + /// ``` + /// use itertools::{Itertools, Position}; + /// + /// let it = (0..4).with_position(); + /// itertools::assert_equal(it, + /// vec![Position::First(0), + /// Position::Middle(1), + /// Position::Middle(2), + /// Position::Last(3)]); + /// + /// let it = (0..1).with_position(); + /// itertools::assert_equal(it, vec![Position::Only(0)]); + /// ``` + fn with_position(self) -> WithPosition<Self> + where Self: Sized, + { + with_position::with_position(self) + } + + /// Return an iterator adaptor that yields the indices of all elements + /// satisfying a predicate, counted from the start of the iterator. + /// + /// Equivalent to `iter.enumerate().filter(|(_, v)| predicate(v)).map(|(i, _)| i)`. + /// + /// ``` + /// use itertools::Itertools; + /// + /// let data = vec![1, 2, 3, 3, 4, 6, 7, 9]; + /// itertools::assert_equal(data.iter().positions(|v| v % 2 == 0), vec![1, 4, 5]); + /// + /// itertools::assert_equal(data.iter().positions(|v| v % 2 == 1).rev(), vec![7, 6, 3, 2, 0]); + /// ``` + fn positions<P>(self, predicate: P) -> Positions<Self, P> + where Self: Sized, + P: FnMut(Self::Item) -> bool, + { + adaptors::positions(self, predicate) + } + + /// Return an iterator adaptor that applies a mutating function + /// to each element before yielding it. + /// + /// ``` + /// use itertools::Itertools; + /// + /// let input = vec![vec![1], vec![3, 2, 1]]; + /// let it = input.into_iter().update(|mut v| v.push(0)); + /// itertools::assert_equal(it, vec![vec![1, 0], vec![3, 2, 1, 0]]); + /// ``` + fn update<F>(self, updater: F) -> Update<Self, F> + where Self: Sized, + F: FnMut(&mut Self::Item), + { + adaptors::update(self, updater) + } + + // non-adaptor methods + /// Advances the iterator and returns the next items grouped in a tuple of + /// a specific size (up to 12). + /// + /// If there are enough elements to be grouped in a tuple, then the tuple is + /// returned inside `Some`, otherwise `None` is returned. + /// + /// ``` + /// use itertools::Itertools; + /// + /// let mut iter = 1..5; + /// + /// assert_eq!(Some((1, 2)), iter.next_tuple()); + /// ``` + fn next_tuple<T>(&mut self) -> Option<T> + where Self: Sized + Iterator<Item = T::Item>, + T: traits::HomogeneousTuple + { + T::collect_from_iter_no_buf(self) + } + + /// Collects all items from the iterator into a tuple of a specific size + /// (up to 12). + /// + /// If the number of elements inside the iterator is **exactly** equal to + /// the tuple size, then the tuple is returned inside `Some`, otherwise + /// `None` is returned. + /// + /// ``` + /// use itertools::Itertools; + /// + /// let iter = 1..3; + /// + /// if let Some((x, y)) = iter.collect_tuple() { + /// assert_eq!((x, y), (1, 2)) + /// } else { + /// panic!("Expected two elements") + /// } + /// ``` + fn collect_tuple<T>(mut self) -> Option<T> + where Self: Sized + Iterator<Item = T::Item>, + T: traits::HomogeneousTuple + { + match self.next_tuple() { + elt @ Some(_) => match self.next() { + Some(_) => None, + None => elt, + }, + _ => None + } + } + + + /// Find the position and value of the first element satisfying a predicate. + /// + /// The iterator is not advanced past the first element found. + /// + /// ``` + /// use itertools::Itertools; + /// + /// let text = "Hα"; + /// assert_eq!(text.chars().find_position(|ch| ch.is_lowercase()), Some((1, 'α'))); + /// ``` + fn find_position<P>(&mut self, mut pred: P) -> Option<(usize, Self::Item)> + where P: FnMut(&Self::Item) -> bool + { + for (index, elt) in self.enumerate() { + if pred(&elt) { + return Some((index, elt)); + } + } + None + } + /// Find the value of the first element satisfying a predicate or return the last element, if any. + /// + /// The iterator is not advanced past the first element found. + /// + /// ``` + /// use itertools::Itertools; + /// + /// let numbers = [1, 2, 3, 4]; + /// assert_eq!(numbers.iter().find_or_last(|&&x| x > 5), Some(&4)); + /// assert_eq!(numbers.iter().find_or_last(|&&x| x > 2), Some(&3)); + /// assert_eq!(std::iter::empty::<i32>().find_or_last(|&x| x > 5), None); + /// ``` + fn find_or_last<P>(mut self, mut predicate: P) -> Option<Self::Item> + where Self: Sized, + P: FnMut(&Self::Item) -> bool, + { + let mut prev = None; + self.find_map(|x| if predicate(&x) { Some(x) } else { prev = Some(x); None }) + .or(prev) + } + /// Find the value of the first element satisfying a predicate or return the first element, if any. + /// + /// The iterator is not advanced past the first element found. + /// + /// ``` + /// use itertools::Itertools; + /// + /// let numbers = [1, 2, 3, 4]; + /// assert_eq!(numbers.iter().find_or_first(|&&x| x > 5), Some(&1)); + /// assert_eq!(numbers.iter().find_or_first(|&&x| x > 2), Some(&3)); + /// assert_eq!(std::iter::empty::<i32>().find_or_first(|&x| x > 5), None); + /// ``` + fn find_or_first<P>(mut self, mut predicate: P) -> Option<Self::Item> + where Self: Sized, + P: FnMut(&Self::Item) -> bool, + { + let first = self.next()?; + Some(if predicate(&first) { + first + } else { + self.find(|x| predicate(x)).unwrap_or(first) + }) + } + /// Returns `true` if the given item is present in this iterator. + /// + /// This method is short-circuiting. If the given item is present in this + /// iterator, this method will consume the iterator up-to-and-including + /// the item. If the given item is not present in this iterator, the + /// iterator will be exhausted. + /// + /// ``` + /// use itertools::Itertools; + /// + /// #[derive(PartialEq, Debug)] + /// enum Enum { A, B, C, D, E, } + /// + /// let mut iter = vec![Enum::A, Enum::B, Enum::C, Enum::D].into_iter(); + /// + /// // search `iter` for `B` + /// assert_eq!(iter.contains(&Enum::B), true); + /// // `B` was found, so the iterator now rests at the item after `B` (i.e, `C`). + /// assert_eq!(iter.next(), Some(Enum::C)); + /// + /// // search `iter` for `E` + /// assert_eq!(iter.contains(&Enum::E), false); + /// // `E` wasn't found, so `iter` is now exhausted + /// assert_eq!(iter.next(), None); + /// ``` + fn contains<Q>(&mut self, query: &Q) -> bool + where + Self: Sized, + Self::Item: Borrow<Q>, + Q: PartialEq, + { + self.any(|x| x.borrow() == query) + } + + /// Check whether all elements compare equal. + /// + /// Empty iterators are considered to have equal elements: + /// + /// ``` + /// use itertools::Itertools; + /// + /// let data = vec![1, 1, 1, 2, 2, 3, 3, 3, 4, 5, 5]; + /// assert!(!data.iter().all_equal()); + /// assert!(data[0..3].iter().all_equal()); + /// assert!(data[3..5].iter().all_equal()); + /// assert!(data[5..8].iter().all_equal()); + /// + /// let data : Option<usize> = None; + /// assert!(data.into_iter().all_equal()); + /// ``` + fn all_equal(&mut self) -> bool + where Self: Sized, + Self::Item: PartialEq, + { + match self.next() { + None => true, + Some(a) => self.all(|x| a == x), + } + } + + /// Check whether all elements are unique (non equal). + /// + /// Empty iterators are considered to have unique elements: + /// + /// ``` + /// use itertools::Itertools; + /// + /// let data = vec![1, 2, 3, 4, 1, 5]; + /// assert!(!data.iter().all_unique()); + /// assert!(data[0..4].iter().all_unique()); + /// assert!(data[1..6].iter().all_unique()); + /// + /// let data : Option<usize> = None; + /// assert!(data.into_iter().all_unique()); + /// ``` + #[cfg(feature = "use_std")] + fn all_unique(&mut self) -> bool + where Self: Sized, + Self::Item: Eq + Hash + { + let mut used = HashSet::new(); + self.all(move |elt| used.insert(elt)) + } + + /// Consume the first `n` elements from the iterator eagerly, + /// and return the same iterator again. + /// + /// It works similarly to *.skip(* `n` *)* except it is eager and + /// preserves the iterator type. + /// + /// ``` + /// use itertools::Itertools; + /// + /// let mut iter = "αβγ".chars().dropping(2); + /// itertools::assert_equal(iter, "γ".chars()); + /// ``` + /// + /// *Fusing notes: if the iterator is exhausted by dropping, + /// the result of calling `.next()` again depends on the iterator implementation.* + fn dropping(mut self, n: usize) -> Self + where Self: Sized + { + if n > 0 { + self.nth(n - 1); + } + self + } + + /// Consume the last `n` elements from the iterator eagerly, + /// and return the same iterator again. + /// + /// This is only possible on double ended iterators. `n` may be + /// larger than the number of elements. + /// + /// Note: This method is eager, dropping the back elements immediately and + /// preserves the iterator type. + /// + /// ``` + /// use itertools::Itertools; + /// + /// let init = vec![0, 3, 6, 9].into_iter().dropping_back(1); + /// itertools::assert_equal(init, vec![0, 3, 6]); + /// ``` + fn dropping_back(mut self, n: usize) -> Self + where Self: Sized, + Self: DoubleEndedIterator + { + if n > 0 { + (&mut self).rev().nth(n - 1); + } + self + } + + /// Run the closure `f` eagerly on each element of the iterator. + /// + /// Consumes the iterator until its end. + /// + /// ``` + /// use std::sync::mpsc::channel; + /// use itertools::Itertools; + /// + /// let (tx, rx) = channel(); + /// + /// // use .foreach() to apply a function to each value -- sending it + /// (0..5).map(|x| x * 2 + 1).foreach(|x| { tx.send(x).unwrap(); } ); + /// + /// drop(tx); + /// + /// itertools::assert_equal(rx.iter(), vec![1, 3, 5, 7, 9]); + /// ``` + #[deprecated(note="Use .for_each() instead", since="0.8.0")] + fn foreach<F>(self, f: F) + where F: FnMut(Self::Item), + Self: Sized, + { + self.for_each(f); + } + + /// Combine all an iterator's elements into one element by using [`Extend`]. + /// + /// This combinator will extend the first item with each of the rest of the + /// items of the iterator. If the iterator is empty, the default value of + /// `I::Item` is returned. + /// + /// ```rust + /// use itertools::Itertools; + /// + /// let input = vec![vec![1], vec![2, 3], vec![4, 5, 6]]; + /// assert_eq!(input.into_iter().concat(), + /// vec![1, 2, 3, 4, 5, 6]); + /// ``` + fn concat(self) -> Self::Item + where Self: Sized, + Self::Item: Extend<<<Self as Iterator>::Item as IntoIterator>::Item> + IntoIterator + Default + { + concat(self) + } + + /// `.collect_vec()` is simply a type specialization of [`Iterator::collect`], + /// for convenience. + #[cfg(feature = "use_alloc")] + fn collect_vec(self) -> Vec<Self::Item> + where Self: Sized + { + self.collect() + } + + /// `.try_collect()` is more convenient way of writing + /// `.collect::<Result<_, _>>()` + /// + /// # Example + /// + /// ``` + /// use std::{fs, io}; + /// use itertools::Itertools; + /// + /// fn process_dir_entries(entries: &[fs::DirEntry]) { + /// // ... + /// } + /// + /// fn do_stuff() -> std::io::Result<()> { + /// let entries: Vec<_> = fs::read_dir(".")?.try_collect()?; + /// process_dir_entries(&entries); + /// + /// Ok(()) + /// } + /// ``` + #[cfg(feature = "use_alloc")] + fn try_collect<T, U, E>(self) -> Result<U, E> + where + Self: Sized + Iterator<Item = Result<T, E>>, + Result<U, E>: FromIterator<Result<T, E>>, + { + self.collect() + } + + /// Assign to each reference in `self` from the `from` iterator, + /// stopping at the shortest of the two iterators. + /// + /// The `from` iterator is queried for its next element before the `self` + /// iterator, and if either is exhausted the method is done. + /// + /// Return the number of elements written. + /// + /// ``` + /// use itertools::Itertools; + /// + /// let mut xs = [0; 4]; + /// xs.iter_mut().set_from(1..); + /// assert_eq!(xs, [1, 2, 3, 4]); + /// ``` + #[inline] + fn set_from<'a, A: 'a, J>(&mut self, from: J) -> usize + where Self: Iterator<Item = &'a mut A>, + J: IntoIterator<Item = A> + { + let mut count = 0; + for elt in from { + match self.next() { + None => break, + Some(ptr) => *ptr = elt, + } + count += 1; + } + count + } + + /// Combine all iterator elements into one String, separated by `sep`. + /// + /// Use the `Display` implementation of each element. + /// + /// ``` + /// use itertools::Itertools; + /// + /// assert_eq!(["a", "b", "c"].iter().join(", "), "a, b, c"); + /// assert_eq!([1, 2, 3].iter().join(", "), "1, 2, 3"); + /// ``` + #[cfg(feature = "use_alloc")] + fn join(&mut self, sep: &str) -> String + where Self::Item: std::fmt::Display + { + match self.next() { + None => String::new(), + Some(first_elt) => { + // estimate lower bound of capacity needed + let (lower, _) = self.size_hint(); + let mut result = String::with_capacity(sep.len() * lower); + write!(&mut result, "{}", first_elt).unwrap(); + self.for_each(|elt| { + result.push_str(sep); + write!(&mut result, "{}", elt).unwrap(); + }); + result + } + } + } + + /// Format all iterator elements, separated by `sep`. + /// + /// All elements are formatted (any formatting trait) + /// with `sep` inserted between each element. + /// + /// **Panics** if the formatter helper is formatted more than once. + /// + /// ``` + /// use itertools::Itertools; + /// + /// let data = [1.1, 2.71828, -3.]; + /// assert_eq!( + /// format!("{:.2}", data.iter().format(", ")), + /// "1.10, 2.72, -3.00"); + /// ``` + fn format(self, sep: &str) -> Format<Self> + where Self: Sized, + { + format::new_format_default(self, sep) + } + + /// Format all iterator elements, separated by `sep`. + /// + /// This is a customizable version of [`.format()`](Itertools::format). + /// + /// The supplied closure `format` is called once per iterator element, + /// with two arguments: the element and a callback that takes a + /// `&Display` value, i.e. any reference to type that implements `Display`. + /// + /// Using `&format_args!(...)` is the most versatile way to apply custom + /// element formatting. The callback can be called multiple times if needed. + /// + /// **Panics** if the formatter helper is formatted more than once. + /// + /// ``` + /// use itertools::Itertools; + /// + /// let data = [1.1, 2.71828, -3.]; + /// let data_formatter = data.iter().format_with(", ", |elt, f| f(&format_args!("{:.2}", elt))); + /// assert_eq!(format!("{}", data_formatter), + /// "1.10, 2.72, -3.00"); + /// + /// // .format_with() is recursively composable + /// let matrix = [[1., 2., 3.], + /// [4., 5., 6.]]; + /// let matrix_formatter = matrix.iter().format_with("\n", |row, f| { + /// f(&row.iter().format_with(", ", |elt, g| g(&elt))) + /// }); + /// assert_eq!(format!("{}", matrix_formatter), + /// "1, 2, 3\n4, 5, 6"); + /// + /// + /// ``` + fn format_with<F>(self, sep: &str, format: F) -> FormatWith<Self, F> + where Self: Sized, + F: FnMut(Self::Item, &mut dyn FnMut(&dyn fmt::Display) -> fmt::Result) -> fmt::Result, + { + format::new_format(self, sep, format) + } + + /// See [`.fold_ok()`](Itertools::fold_ok). + #[deprecated(note="Use .fold_ok() instead", since="0.10.0")] + fn fold_results<A, E, B, F>(&mut self, start: B, f: F) -> Result<B, E> + where Self: Iterator<Item = Result<A, E>>, + F: FnMut(B, A) -> B + { + self.fold_ok(start, f) + } + + /// Fold `Result` values from an iterator. + /// + /// Only `Ok` values are folded. If no error is encountered, the folded + /// value is returned inside `Ok`. Otherwise, the operation terminates + /// and returns the first `Err` value it encounters. No iterator elements are + /// consumed after the first error. + /// + /// The first accumulator value is the `start` parameter. + /// Each iteration passes the accumulator value and the next value inside `Ok` + /// to the fold function `f` and its return value becomes the new accumulator value. + /// + /// For example the sequence *Ok(1), Ok(2), Ok(3)* will result in a + /// computation like this: + /// + /// ```ignore + /// let mut accum = start; + /// accum = f(accum, 1); + /// accum = f(accum, 2); + /// accum = f(accum, 3); + /// ``` + /// + /// With a `start` value of 0 and an addition as folding function, + /// this effectively results in *((0 + 1) + 2) + 3* + /// + /// ``` + /// use std::ops::Add; + /// use itertools::Itertools; + /// + /// let values = [1, 2, -2, -1, 2, 1]; + /// assert_eq!( + /// values.iter() + /// .map(Ok::<_, ()>) + /// .fold_ok(0, Add::add), + /// Ok(3) + /// ); + /// assert!( + /// values.iter() + /// .map(|&x| if x >= 0 { Ok(x) } else { Err("Negative number") }) + /// .fold_ok(0, Add::add) + /// .is_err() + /// ); + /// ``` + fn fold_ok<A, E, B, F>(&mut self, mut start: B, mut f: F) -> Result<B, E> + where Self: Iterator<Item = Result<A, E>>, + F: FnMut(B, A) -> B + { + for elt in self { + match elt { + Ok(v) => start = f(start, v), + Err(u) => return Err(u), + } + } + Ok(start) + } + + /// Fold `Option` values from an iterator. + /// + /// Only `Some` values are folded. If no `None` is encountered, the folded + /// value is returned inside `Some`. Otherwise, the operation terminates + /// and returns `None`. No iterator elements are consumed after the `None`. + /// + /// This is the `Option` equivalent to [`fold_ok`](Itertools::fold_ok). + /// + /// ``` + /// use std::ops::Add; + /// use itertools::Itertools; + /// + /// let mut values = vec![Some(1), Some(2), Some(-2)].into_iter(); + /// assert_eq!(values.fold_options(5, Add::add), Some(5 + 1 + 2 - 2)); + /// + /// let mut more_values = vec![Some(2), None, Some(0)].into_iter(); + /// assert!(more_values.fold_options(0, Add::add).is_none()); + /// assert_eq!(more_values.next().unwrap(), Some(0)); + /// ``` + fn fold_options<A, B, F>(&mut self, mut start: B, mut f: F) -> Option<B> + where Self: Iterator<Item = Option<A>>, + F: FnMut(B, A) -> B + { + for elt in self { + match elt { + Some(v) => start = f(start, v), + None => return None, + } + } + Some(start) + } + + /// Accumulator of the elements in the iterator. + /// + /// Like `.fold()`, without a base case. If the iterator is + /// empty, return `None`. With just one element, return it. + /// Otherwise elements are accumulated in sequence using the closure `f`. + /// + /// ``` + /// use itertools::Itertools; + /// + /// assert_eq!((0..10).fold1(|x, y| x + y).unwrap_or(0), 45); + /// assert_eq!((0..0).fold1(|x, y| x * y), None); + /// ``` + #[deprecated(since = "0.10.2", note = "Use `Iterator::reduce` instead")] + fn fold1<F>(mut self, f: F) -> Option<Self::Item> + where F: FnMut(Self::Item, Self::Item) -> Self::Item, + Self: Sized, + { + self.next().map(move |x| self.fold(x, f)) + } + + /// Accumulate the elements in the iterator in a tree-like manner. + /// + /// You can think of it as, while there's more than one item, repeatedly + /// combining adjacent items. It does so in bottom-up-merge-sort order, + /// however, so that it needs only logarithmic stack space. + /// + /// This produces a call tree like the following (where the calls under + /// an item are done after reading that item): + /// + /// ```text + /// 1 2 3 4 5 6 7 + /// │ │ │ │ │ │ │ + /// └─f └─f └─f │ + /// │ │ │ │ + /// └───f └─f + /// │ │ + /// └─────f + /// ``` + /// + /// Which, for non-associative functions, will typically produce a different + /// result than the linear call tree used by [`Iterator::reduce`]: + /// + /// ```text + /// 1 2 3 4 5 6 7 + /// │ │ │ │ │ │ │ + /// └─f─f─f─f─f─f + /// ``` + /// + /// If `f` is associative, prefer the normal [`Iterator::reduce`] instead. + /// + /// ``` + /// use itertools::Itertools; + /// + /// // The same tree as above + /// let num_strings = (1..8).map(|x| x.to_string()); + /// assert_eq!(num_strings.tree_fold1(|x, y| format!("f({}, {})", x, y)), + /// Some(String::from("f(f(f(1, 2), f(3, 4)), f(f(5, 6), 7))"))); + /// + /// // Like fold1, an empty iterator produces None + /// assert_eq!((0..0).tree_fold1(|x, y| x * y), None); + /// + /// // tree_fold1 matches fold1 for associative operations... + /// assert_eq!((0..10).tree_fold1(|x, y| x + y), + /// (0..10).fold1(|x, y| x + y)); + /// // ...but not for non-associative ones + /// assert_ne!((0..10).tree_fold1(|x, y| x - y), + /// (0..10).fold1(|x, y| x - y)); + /// ``` + fn tree_fold1<F>(mut self, mut f: F) -> Option<Self::Item> + where F: FnMut(Self::Item, Self::Item) -> Self::Item, + Self: Sized, + { + type State<T> = Result<T, Option<T>>; + + fn inner0<T, II, FF>(it: &mut II, f: &mut FF) -> State<T> + where + II: Iterator<Item = T>, + FF: FnMut(T, T) -> T + { + // This function could be replaced with `it.next().ok_or(None)`, + // but half the useful tree_fold1 work is combining adjacent items, + // so put that in a form that LLVM is more likely to optimize well. + + let a = + if let Some(v) = it.next() { v } + else { return Err(None) }; + let b = + if let Some(v) = it.next() { v } + else { return Err(Some(a)) }; + Ok(f(a, b)) + } + + fn inner<T, II, FF>(stop: usize, it: &mut II, f: &mut FF) -> State<T> + where + II: Iterator<Item = T>, + FF: FnMut(T, T) -> T + { + let mut x = inner0(it, f)?; + for height in 0..stop { + // Try to get another tree the same size with which to combine it, + // creating a new tree that's twice as big for next time around. + let next = + if height == 0 { + inner0(it, f) + } else { + inner(height, it, f) + }; + match next { + Ok(y) => x = f(x, y), + + // If we ran out of items, combine whatever we did manage + // to get. It's better combined with the current value + // than something in a parent frame, because the tree in + // the parent is always as least as big as this one. + Err(None) => return Err(Some(x)), + Err(Some(y)) => return Err(Some(f(x, y))), + } + } + Ok(x) + } + + match inner(usize::max_value(), &mut self, &mut f) { + Err(x) => x, + _ => unreachable!(), + } + } + + /// An iterator method that applies a function, producing a single, final value. + /// + /// `fold_while()` is basically equivalent to [`Iterator::fold`] but with additional support for + /// early exit via short-circuiting. + /// + /// ``` + /// use itertools::Itertools; + /// use itertools::FoldWhile::{Continue, Done}; + /// + /// let numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]; + /// + /// let mut result = 0; + /// + /// // for loop: + /// for i in &numbers { + /// if *i > 5 { + /// break; + /// } + /// result = result + i; + /// } + /// + /// // fold: + /// let result2 = numbers.iter().fold(0, |acc, x| { + /// if *x > 5 { acc } else { acc + x } + /// }); + /// + /// // fold_while: + /// let result3 = numbers.iter().fold_while(0, |acc, x| { + /// if *x > 5 { Done(acc) } else { Continue(acc + x) } + /// }).into_inner(); + /// + /// // they're the same + /// assert_eq!(result, result2); + /// assert_eq!(result2, result3); + /// ``` + /// + /// The big difference between the computations of `result2` and `result3` is that while + /// `fold()` called the provided closure for every item of the callee iterator, + /// `fold_while()` actually stopped iterating as soon as it encountered `Fold::Done(_)`. + fn fold_while<B, F>(&mut self, init: B, mut f: F) -> FoldWhile<B> + where Self: Sized, + F: FnMut(B, Self::Item) -> FoldWhile<B> + { + use Result::{ + Ok as Continue, + Err as Break, + }; + + let result = self.try_fold(init, #[inline(always)] |acc, v| + match f(acc, v) { + FoldWhile::Continue(acc) => Continue(acc), + FoldWhile::Done(acc) => Break(acc), + } + ); + + match result { + Continue(acc) => FoldWhile::Continue(acc), + Break(acc) => FoldWhile::Done(acc), + } + } + + /// Iterate over the entire iterator and add all the elements. + /// + /// An empty iterator returns `None`, otherwise `Some(sum)`. + /// + /// # Panics + /// + /// When calling `sum1()` and a primitive integer type is being returned, this + /// method will panic if the computation overflows and debug assertions are + /// enabled. + /// + /// # Examples + /// + /// ``` + /// use itertools::Itertools; + /// + /// let empty_sum = (1..1).sum1::<i32>(); + /// assert_eq!(empty_sum, None); + /// + /// let nonempty_sum = (1..11).sum1::<i32>(); + /// assert_eq!(nonempty_sum, Some(55)); + /// ``` + fn sum1<S>(mut self) -> Option<S> + where Self: Sized, + S: std::iter::Sum<Self::Item>, + { + self.next() + .map(|first| once(first).chain(self).sum()) + } + + /// Iterate over the entire iterator and multiply all the elements. + /// + /// An empty iterator returns `None`, otherwise `Some(product)`. + /// + /// # Panics + /// + /// When calling `product1()` and a primitive integer type is being returned, + /// method will panic if the computation overflows and debug assertions are + /// enabled. + /// + /// # Examples + /// ``` + /// use itertools::Itertools; + /// + /// let empty_product = (1..1).product1::<i32>(); + /// assert_eq!(empty_product, None); + /// + /// let nonempty_product = (1..11).product1::<i32>(); + /// assert_eq!(nonempty_product, Some(3628800)); + /// ``` + fn product1<P>(mut self) -> Option<P> + where Self: Sized, + P: std::iter::Product<Self::Item>, + { + self.next() + .map(|first| once(first).chain(self).product()) + } + + /// Sort all iterator elements into a new iterator in ascending order. + /// + /// **Note:** This consumes the entire iterator, uses the + /// [`slice::sort_unstable`] method and returns the result as a new + /// iterator that owns its elements. + /// + /// The sorted iterator, if directly collected to a `Vec`, is converted + /// without any extra copying or allocation cost. + /// + /// ``` + /// use itertools::Itertools; + /// + /// // sort the letters of the text in ascending order + /// let text = "bdacfe"; + /// itertools::assert_equal(text.chars().sorted_unstable(), + /// "abcdef".chars()); + /// ``` + #[cfg(feature = "use_alloc")] + fn sorted_unstable(self) -> VecIntoIter<Self::Item> + where Self: Sized, + Self::Item: Ord + { + // Use .sort_unstable() directly since it is not quite identical with + // .sort_by(Ord::cmp) + let mut v = Vec::from_iter(self); + v.sort_unstable(); + v.into_iter() + } + + /// Sort all iterator elements into a new iterator in ascending order. + /// + /// **Note:** This consumes the entire iterator, uses the + /// [`slice::sort_unstable_by`] method and returns the result as a new + /// iterator that owns its elements. + /// + /// The sorted iterator, if directly collected to a `Vec`, is converted + /// without any extra copying or allocation cost. + /// + /// ``` + /// use itertools::Itertools; + /// + /// // sort people in descending order by age + /// let people = vec![("Jane", 20), ("John", 18), ("Jill", 30), ("Jack", 27)]; + /// + /// let oldest_people_first = people + /// .into_iter() + /// .sorted_unstable_by(|a, b| Ord::cmp(&b.1, &a.1)) + /// .map(|(person, _age)| person); + /// + /// itertools::assert_equal(oldest_people_first, + /// vec!["Jill", "Jack", "Jane", "John"]); + /// ``` + #[cfg(feature = "use_alloc")] + fn sorted_unstable_by<F>(self, cmp: F) -> VecIntoIter<Self::Item> + where Self: Sized, + F: FnMut(&Self::Item, &Self::Item) -> Ordering, + { + let mut v = Vec::from_iter(self); + v.sort_unstable_by(cmp); + v.into_iter() + } + + /// Sort all iterator elements into a new iterator in ascending order. + /// + /// **Note:** This consumes the entire iterator, uses the + /// [`slice::sort_unstable_by_key`] method and returns the result as a new + /// iterator that owns its elements. + /// + /// The sorted iterator, if directly collected to a `Vec`, is converted + /// without any extra copying or allocation cost. + /// + /// ``` + /// use itertools::Itertools; + /// + /// // sort people in descending order by age + /// let people = vec![("Jane", 20), ("John", 18), ("Jill", 30), ("Jack", 27)]; + /// + /// let oldest_people_first = people + /// .into_iter() + /// .sorted_unstable_by_key(|x| -x.1) + /// .map(|(person, _age)| person); + /// + /// itertools::assert_equal(oldest_people_first, + /// vec!["Jill", "Jack", "Jane", "John"]); + /// ``` + #[cfg(feature = "use_alloc")] + fn sorted_unstable_by_key<K, F>(self, f: F) -> VecIntoIter<Self::Item> + where Self: Sized, + K: Ord, + F: FnMut(&Self::Item) -> K, + { + let mut v = Vec::from_iter(self); + v.sort_unstable_by_key(f); + v.into_iter() + } + + /// Sort all iterator elements into a new iterator in ascending order. + /// + /// **Note:** This consumes the entire iterator, uses the + /// [`slice::sort`] method and returns the result as a new + /// iterator that owns its elements. + /// + /// The sorted iterator, if directly collected to a `Vec`, is converted + /// without any extra copying or allocation cost. + /// + /// ``` + /// use itertools::Itertools; + /// + /// // sort the letters of the text in ascending order + /// let text = "bdacfe"; + /// itertools::assert_equal(text.chars().sorted(), + /// "abcdef".chars()); + /// ``` + #[cfg(feature = "use_alloc")] + fn sorted(self) -> VecIntoIter<Self::Item> + where Self: Sized, + Self::Item: Ord + { + // Use .sort() directly since it is not quite identical with + // .sort_by(Ord::cmp) + let mut v = Vec::from_iter(self); + v.sort(); + v.into_iter() + } + + /// Sort all iterator elements into a new iterator in ascending order. + /// + /// **Note:** This consumes the entire iterator, uses the + /// [`slice::sort_by`] method and returns the result as a new + /// iterator that owns its elements. + /// + /// The sorted iterator, if directly collected to a `Vec`, is converted + /// without any extra copying or allocation cost. + /// + /// ``` + /// use itertools::Itertools; + /// + /// // sort people in descending order by age + /// let people = vec![("Jane", 20), ("John", 18), ("Jill", 30), ("Jack", 27)]; + /// + /// let oldest_people_first = people + /// .into_iter() + /// .sorted_by(|a, b| Ord::cmp(&b.1, &a.1)) + /// .map(|(person, _age)| person); + /// + /// itertools::assert_equal(oldest_people_first, + /// vec!["Jill", "Jack", "Jane", "John"]); + /// ``` + #[cfg(feature = "use_alloc")] + fn sorted_by<F>(self, cmp: F) -> VecIntoIter<Self::Item> + where Self: Sized, + F: FnMut(&Self::Item, &Self::Item) -> Ordering, + { + let mut v = Vec::from_iter(self); + v.sort_by(cmp); + v.into_iter() + } + + /// Sort all iterator elements into a new iterator in ascending order. + /// + /// **Note:** This consumes the entire iterator, uses the + /// [`slice::sort_by_key`] method and returns the result as a new + /// iterator that owns its elements. + /// + /// The sorted iterator, if directly collected to a `Vec`, is converted + /// without any extra copying or allocation cost. + /// + /// ``` + /// use itertools::Itertools; + /// + /// // sort people in descending order by age + /// let people = vec![("Jane", 20), ("John", 18), ("Jill", 30), ("Jack", 27)]; + /// + /// let oldest_people_first = people + /// .into_iter() + /// .sorted_by_key(|x| -x.1) + /// .map(|(person, _age)| person); + /// + /// itertools::assert_equal(oldest_people_first, + /// vec!["Jill", "Jack", "Jane", "John"]); + /// ``` + #[cfg(feature = "use_alloc")] + fn sorted_by_key<K, F>(self, f: F) -> VecIntoIter<Self::Item> + where Self: Sized, + K: Ord, + F: FnMut(&Self::Item) -> K, + { + let mut v = Vec::from_iter(self); + v.sort_by_key(f); + v.into_iter() + } + + /// Sort all iterator elements into a new iterator in ascending order. The key function is + /// called exactly once per key. + /// + /// **Note:** This consumes the entire iterator, uses the + /// [`slice::sort_by_cached_key`] method and returns the result as a new + /// iterator that owns its elements. + /// + /// The sorted iterator, if directly collected to a `Vec`, is converted + /// without any extra copying or allocation cost. + /// + /// ``` + /// use itertools::Itertools; + /// + /// // sort people in descending order by age + /// let people = vec![("Jane", 20), ("John", 18), ("Jill", 30), ("Jack", 27)]; + /// + /// let oldest_people_first = people + /// .into_iter() + /// .sorted_by_cached_key(|x| -x.1) + /// .map(|(person, _age)| person); + /// + /// itertools::assert_equal(oldest_people_first, + /// vec!["Jill", "Jack", "Jane", "John"]); + /// ``` + #[cfg(feature = "use_alloc")] + fn sorted_by_cached_key<K, F>(self, f: F) -> VecIntoIter<Self::Item> + where + Self: Sized, + K: Ord, + F: FnMut(&Self::Item) -> K, + { + let mut v = Vec::from_iter(self); + v.sort_by_cached_key(f); + v.into_iter() + } + + /// Sort the k smallest elements into a new iterator, in ascending order. + /// + /// **Note:** This consumes the entire iterator, and returns the result + /// as a new iterator that owns its elements. If the input contains + /// less than k elements, the result is equivalent to `self.sorted()`. + /// + /// This is guaranteed to use `k * sizeof(Self::Item) + O(1)` memory + /// and `O(n log k)` time, with `n` the number of elements in the input. + /// + /// The sorted iterator, if directly collected to a `Vec`, is converted + /// without any extra copying or allocation cost. + /// + /// **Note:** This is functionally-equivalent to `self.sorted().take(k)` + /// but much more efficient. + /// + /// ``` + /// use itertools::Itertools; + /// + /// // A random permutation of 0..15 + /// let numbers = vec![6, 9, 1, 14, 0, 4, 8, 7, 11, 2, 10, 3, 13, 12, 5]; + /// + /// let five_smallest = numbers + /// .into_iter() + /// .k_smallest(5); + /// + /// itertools::assert_equal(five_smallest, 0..5); + /// ``` + #[cfg(feature = "use_alloc")] + fn k_smallest(self, k: usize) -> VecIntoIter<Self::Item> + where Self: Sized, + Self::Item: Ord + { + crate::k_smallest::k_smallest(self, k) + .into_sorted_vec() + .into_iter() + } + + /// Collect all iterator elements into one of two + /// partitions. Unlike [`Iterator::partition`], each partition may + /// have a distinct type. + /// + /// ``` + /// use itertools::{Itertools, Either}; + /// + /// let successes_and_failures = vec![Ok(1), Err(false), Err(true), Ok(2)]; + /// + /// let (successes, failures): (Vec<_>, Vec<_>) = successes_and_failures + /// .into_iter() + /// .partition_map(|r| { + /// match r { + /// Ok(v) => Either::Left(v), + /// Err(v) => Either::Right(v), + /// } + /// }); + /// + /// assert_eq!(successes, [1, 2]); + /// assert_eq!(failures, [false, true]); + /// ``` + fn partition_map<A, B, F, L, R>(self, mut predicate: F) -> (A, B) + where Self: Sized, + F: FnMut(Self::Item) -> Either<L, R>, + A: Default + Extend<L>, + B: Default + Extend<R>, + { + let mut left = A::default(); + let mut right = B::default(); + + self.for_each(|val| match predicate(val) { + Either::Left(v) => left.extend(Some(v)), + Either::Right(v) => right.extend(Some(v)), + }); + + (left, right) + } + + /// Partition a sequence of `Result`s into one list of all the `Ok` elements + /// and another list of all the `Err` elements. + /// + /// ``` + /// use itertools::Itertools; + /// + /// let successes_and_failures = vec![Ok(1), Err(false), Err(true), Ok(2)]; + /// + /// let (successes, failures): (Vec<_>, Vec<_>) = successes_and_failures + /// .into_iter() + /// .partition_result(); + /// + /// assert_eq!(successes, [1, 2]); + /// assert_eq!(failures, [false, true]); + /// ``` + fn partition_result<A, B, T, E>(self) -> (A, B) + where + Self: Iterator<Item = Result<T, E>> + Sized, + A: Default + Extend<T>, + B: Default + Extend<E>, + { + self.partition_map(|r| match r { + Ok(v) => Either::Left(v), + Err(v) => Either::Right(v), + }) + } + + /// Return a `HashMap` of keys mapped to `Vec`s of values. Keys and values + /// are taken from `(Key, Value)` tuple pairs yielded by the input iterator. + /// + /// Essentially a shorthand for `.into_grouping_map().collect::<Vec<_>>()`. + /// + /// ``` + /// use itertools::Itertools; + /// + /// let data = vec![(0, 10), (2, 12), (3, 13), (0, 20), (3, 33), (2, 42)]; + /// let lookup = data.into_iter().into_group_map(); + /// + /// assert_eq!(lookup[&0], vec![10, 20]); + /// assert_eq!(lookup.get(&1), None); + /// assert_eq!(lookup[&2], vec![12, 42]); + /// assert_eq!(lookup[&3], vec![13, 33]); + /// ``` + #[cfg(feature = "use_std")] + fn into_group_map<K, V>(self) -> HashMap<K, Vec<V>> + where Self: Iterator<Item=(K, V)> + Sized, + K: Hash + Eq, + { + group_map::into_group_map(self) + } + + /// Return an `Iterator` on a `HashMap`. Keys mapped to `Vec`s of values. The key is specified + /// in the closure. + /// + /// Essentially a shorthand for `.into_grouping_map_by(f).collect::<Vec<_>>()`. + /// + /// ``` + /// use itertools::Itertools; + /// use std::collections::HashMap; + /// + /// let data = vec![(0, 10), (2, 12), (3, 13), (0, 20), (3, 33), (2, 42)]; + /// let lookup: HashMap<u32,Vec<(u32, u32)>> = + /// data.clone().into_iter().into_group_map_by(|a| a.0); + /// + /// assert_eq!(lookup[&0], vec![(0,10),(0,20)]); + /// assert_eq!(lookup.get(&1), None); + /// assert_eq!(lookup[&2], vec![(2,12), (2,42)]); + /// assert_eq!(lookup[&3], vec![(3,13), (3,33)]); + /// + /// assert_eq!( + /// data.into_iter() + /// .into_group_map_by(|x| x.0) + /// .into_iter() + /// .map(|(key, values)| (key, values.into_iter().fold(0,|acc, (_,v)| acc + v ))) + /// .collect::<HashMap<u32,u32>>()[&0], + /// 30, + /// ); + /// ``` + #[cfg(feature = "use_std")] + fn into_group_map_by<K, V, F>(self, f: F) -> HashMap<K, Vec<V>> + where + Self: Iterator<Item=V> + Sized, + K: Hash + Eq, + F: Fn(&V) -> K, + { + group_map::into_group_map_by(self, f) + } + + /// Constructs a `GroupingMap` to be used later with one of the efficient + /// group-and-fold operations it allows to perform. + /// + /// The input iterator must yield item in the form of `(K, V)` where the + /// value of type `K` will be used as key to identify the groups and the + /// value of type `V` as value for the folding operation. + /// + /// See [`GroupingMap`] for more informations + /// on what operations are available. + #[cfg(feature = "use_std")] + fn into_grouping_map<K, V>(self) -> GroupingMap<Self> + where Self: Iterator<Item=(K, V)> + Sized, + K: Hash + Eq, + { + grouping_map::new(self) + } + + /// Constructs a `GroupingMap` to be used later with one of the efficient + /// group-and-fold operations it allows to perform. + /// + /// The values from this iterator will be used as values for the folding operation + /// while the keys will be obtained from the values by calling `key_mapper`. + /// + /// See [`GroupingMap`] for more informations + /// on what operations are available. + #[cfg(feature = "use_std")] + fn into_grouping_map_by<K, V, F>(self, key_mapper: F) -> GroupingMapBy<Self, F> + where Self: Iterator<Item=V> + Sized, + K: Hash + Eq, + F: FnMut(&V) -> K + { + grouping_map::new(grouping_map::MapForGrouping::new(self, key_mapper)) + } + + /// Return all minimum elements of an iterator. + /// + /// # Examples + /// + /// ``` + /// use itertools::Itertools; + /// + /// let a: [i32; 0] = []; + /// assert_eq!(a.iter().min_set(), Vec::<&i32>::new()); + /// + /// let a = [1]; + /// assert_eq!(a.iter().min_set(), vec![&1]); + /// + /// let a = [1, 2, 3, 4, 5]; + /// assert_eq!(a.iter().min_set(), vec![&1]); + /// + /// let a = [1, 1, 1, 1]; + /// assert_eq!(a.iter().min_set(), vec![&1, &1, &1, &1]); + /// ``` + /// + /// The elements can be floats but no particular result is guaranteed + /// if an element is NaN. + #[cfg(feature = "use_std")] + fn min_set(self) -> Vec<Self::Item> + where Self: Sized, Self::Item: Ord + { + extrema_set::min_set_impl(self, |_| (), |x, y, _, _| x.cmp(y)) + } + + /// Return all minimum elements of an iterator, as determined by + /// the specified function. + /// + /// # Examples + /// + /// ``` + /// # use std::cmp::Ordering; + /// use itertools::Itertools; + /// + /// let a: [(i32, i32); 0] = []; + /// assert_eq!(a.iter().min_set_by(|_, _| Ordering::Equal), Vec::<&(i32, i32)>::new()); + /// + /// let a = [(1, 2)]; + /// assert_eq!(a.iter().min_set_by(|&&(k1,_), &&(k2, _)| k1.cmp(&k2)), vec![&(1, 2)]); + /// + /// let a = [(1, 2), (2, 2), (3, 9), (4, 8), (5, 9)]; + /// assert_eq!(a.iter().min_set_by(|&&(_,k1), &&(_,k2)| k1.cmp(&k2)), vec![&(1, 2), &(2, 2)]); + /// + /// let a = [(1, 2), (1, 3), (1, 4), (1, 5)]; + /// assert_eq!(a.iter().min_set_by(|&&(k1,_), &&(k2, _)| k1.cmp(&k2)), vec![&(1, 2), &(1, 3), &(1, 4), &(1, 5)]); + /// ``` + /// + /// The elements can be floats but no particular result is guaranteed + /// if an element is NaN. + #[cfg(feature = "use_std")] + fn min_set_by<F>(self, mut compare: F) -> Vec<Self::Item> + where Self: Sized, F: FnMut(&Self::Item, &Self::Item) -> Ordering + { + extrema_set::min_set_impl( + self, + |_| (), + |x, y, _, _| compare(x, y) + ) + } + + /// Return all minimum elements of an iterator, as determined by + /// the specified function. + /// + /// # Examples + /// + /// ``` + /// use itertools::Itertools; + /// + /// let a: [(i32, i32); 0] = []; + /// assert_eq!(a.iter().min_set_by_key(|_| ()), Vec::<&(i32, i32)>::new()); + /// + /// let a = [(1, 2)]; + /// assert_eq!(a.iter().min_set_by_key(|&&(k,_)| k), vec![&(1, 2)]); + /// + /// let a = [(1, 2), (2, 2), (3, 9), (4, 8), (5, 9)]; + /// assert_eq!(a.iter().min_set_by_key(|&&(_, k)| k), vec![&(1, 2), &(2, 2)]); + /// + /// let a = [(1, 2), (1, 3), (1, 4), (1, 5)]; + /// assert_eq!(a.iter().min_set_by_key(|&&(k, _)| k), vec![&(1, 2), &(1, 3), &(1, 4), &(1, 5)]); + /// ``` + /// + /// The elements can be floats but no particular result is guaranteed + /// if an element is NaN. + #[cfg(feature = "use_std")] + fn min_set_by_key<K, F>(self, key: F) -> Vec<Self::Item> + where Self: Sized, K: Ord, F: FnMut(&Self::Item) -> K + { + extrema_set::min_set_impl(self, key, |_, _, kx, ky| kx.cmp(ky)) + } + + /// Return all maximum elements of an iterator. + /// + /// # Examples + /// + /// ``` + /// use itertools::Itertools; + /// + /// let a: [i32; 0] = []; + /// assert_eq!(a.iter().max_set(), Vec::<&i32>::new()); + /// + /// let a = [1]; + /// assert_eq!(a.iter().max_set(), vec![&1]); + /// + /// let a = [1, 2, 3, 4, 5]; + /// assert_eq!(a.iter().max_set(), vec![&5]); + /// + /// let a = [1, 1, 1, 1]; + /// assert_eq!(a.iter().max_set(), vec![&1, &1, &1, &1]); + /// ``` + /// + /// The elements can be floats but no particular result is guaranteed + /// if an element is NaN. + #[cfg(feature = "use_std")] + fn max_set(self) -> Vec<Self::Item> + where Self: Sized, Self::Item: Ord + { + extrema_set::max_set_impl(self, |_| (), |x, y, _, _| x.cmp(y)) + } + + /// Return all maximum elements of an iterator, as determined by + /// the specified function. + /// + /// # Examples + /// + /// ``` + /// # use std::cmp::Ordering; + /// use itertools::Itertools; + /// + /// let a: [(i32, i32); 0] = []; + /// assert_eq!(a.iter().max_set_by(|_, _| Ordering::Equal), Vec::<&(i32, i32)>::new()); + /// + /// let a = [(1, 2)]; + /// assert_eq!(a.iter().max_set_by(|&&(k1,_), &&(k2, _)| k1.cmp(&k2)), vec![&(1, 2)]); + /// + /// let a = [(1, 2), (2, 2), (3, 9), (4, 8), (5, 9)]; + /// assert_eq!(a.iter().max_set_by(|&&(_,k1), &&(_,k2)| k1.cmp(&k2)), vec![&(3, 9), &(5, 9)]); + /// + /// let a = [(1, 2), (1, 3), (1, 4), (1, 5)]; + /// assert_eq!(a.iter().max_set_by(|&&(k1,_), &&(k2, _)| k1.cmp(&k2)), vec![&(1, 2), &(1, 3), &(1, 4), &(1, 5)]); + /// ``` + /// + /// The elements can be floats but no particular result is guaranteed + /// if an element is NaN. + #[cfg(feature = "use_std")] + fn max_set_by<F>(self, mut compare: F) -> Vec<Self::Item> + where Self: Sized, F: FnMut(&Self::Item, &Self::Item) -> Ordering + { + extrema_set::max_set_impl( + self, + |_| (), + |x, y, _, _| compare(x, y) + ) + } + + /// Return all minimum elements of an iterator, as determined by + /// the specified function. + /// + /// # Examples + /// + /// ``` + /// use itertools::Itertools; + /// + /// let a: [(i32, i32); 0] = []; + /// assert_eq!(a.iter().max_set_by_key(|_| ()), Vec::<&(i32, i32)>::new()); + /// + /// let a = [(1, 2)]; + /// assert_eq!(a.iter().max_set_by_key(|&&(k,_)| k), vec![&(1, 2)]); + /// + /// let a = [(1, 2), (2, 2), (3, 9), (4, 8), (5, 9)]; + /// assert_eq!(a.iter().max_set_by_key(|&&(_, k)| k), vec![&(3, 9), &(5, 9)]); + /// + /// let a = [(1, 2), (1, 3), (1, 4), (1, 5)]; + /// assert_eq!(a.iter().max_set_by_key(|&&(k, _)| k), vec![&(1, 2), &(1, 3), &(1, 4), &(1, 5)]); + /// ``` + /// + /// The elements can be floats but no particular result is guaranteed + /// if an element is NaN. + #[cfg(feature = "use_std")] + fn max_set_by_key<K, F>(self, key: F) -> Vec<Self::Item> + where Self: Sized, K: Ord, F: FnMut(&Self::Item) -> K + { + extrema_set::max_set_impl(self, key, |_, _, kx, ky| kx.cmp(ky)) + } + + /// Return the minimum and maximum elements in the iterator. + /// + /// The return type `MinMaxResult` is an enum of three variants: + /// + /// - `NoElements` if the iterator is empty. + /// - `OneElement(x)` if the iterator has exactly one element. + /// - `MinMax(x, y)` is returned otherwise, where `x <= y`. Two + /// values are equal if and only if there is more than one + /// element in the iterator and all elements are equal. + /// + /// On an iterator of length `n`, `minmax` does `1.5 * n` comparisons, + /// and so is faster than calling `min` and `max` separately which does + /// `2 * n` comparisons. + /// + /// # Examples + /// + /// ``` + /// use itertools::Itertools; + /// use itertools::MinMaxResult::{NoElements, OneElement, MinMax}; + /// + /// let a: [i32; 0] = []; + /// assert_eq!(a.iter().minmax(), NoElements); + /// + /// let a = [1]; + /// assert_eq!(a.iter().minmax(), OneElement(&1)); + /// + /// let a = [1, 2, 3, 4, 5]; + /// assert_eq!(a.iter().minmax(), MinMax(&1, &5)); + /// + /// let a = [1, 1, 1, 1]; + /// assert_eq!(a.iter().minmax(), MinMax(&1, &1)); + /// ``` + /// + /// The elements can be floats but no particular result is guaranteed + /// if an element is NaN. + fn minmax(self) -> MinMaxResult<Self::Item> + where Self: Sized, Self::Item: PartialOrd + { + minmax::minmax_impl(self, |_| (), |x, y, _, _| x < y) + } + + /// Return the minimum and maximum element of an iterator, as determined by + /// the specified function. + /// + /// The return value is a variant of [`MinMaxResult`] like for [`.minmax()`](Itertools::minmax). + /// + /// For the minimum, the first minimal element is returned. For the maximum, + /// the last maximal element wins. This matches the behavior of the standard + /// [`Iterator::min`] and [`Iterator::max`] methods. + /// + /// The keys can be floats but no particular result is guaranteed + /// if a key is NaN. + fn minmax_by_key<K, F>(self, key: F) -> MinMaxResult<Self::Item> + where Self: Sized, K: PartialOrd, F: FnMut(&Self::Item) -> K + { + minmax::minmax_impl(self, key, |_, _, xk, yk| xk < yk) + } + + /// Return the minimum and maximum element of an iterator, as determined by + /// the specified comparison function. + /// + /// The return value is a variant of [`MinMaxResult`] like for [`.minmax()`](Itertools::minmax). + /// + /// For the minimum, the first minimal element is returned. For the maximum, + /// the last maximal element wins. This matches the behavior of the standard + /// [`Iterator::min`] and [`Iterator::max`] methods. + fn minmax_by<F>(self, mut compare: F) -> MinMaxResult<Self::Item> + where Self: Sized, F: FnMut(&Self::Item, &Self::Item) -> Ordering + { + minmax::minmax_impl( + self, + |_| (), + |x, y, _, _| Ordering::Less == compare(x, y) + ) + } + + /// Return the position of the maximum element in the iterator. + /// + /// If several elements are equally maximum, the position of the + /// last of them is returned. + /// + /// # Examples + /// + /// ``` + /// use itertools::Itertools; + /// + /// let a: [i32; 0] = []; + /// assert_eq!(a.iter().position_max(), None); + /// + /// let a = [-3, 0, 1, 5, -10]; + /// assert_eq!(a.iter().position_max(), Some(3)); + /// + /// let a = [1, 1, -1, -1]; + /// assert_eq!(a.iter().position_max(), Some(1)); + /// ``` + fn position_max(self) -> Option<usize> + where Self: Sized, Self::Item: Ord + { + self.enumerate() + .max_by(|x, y| Ord::cmp(&x.1, &y.1)) + .map(|x| x.0) + } + + /// Return the position of the maximum element in the iterator, as + /// determined by the specified function. + /// + /// If several elements are equally maximum, the position of the + /// last of them is returned. + /// + /// # Examples + /// + /// ``` + /// use itertools::Itertools; + /// + /// let a: [i32; 0] = []; + /// assert_eq!(a.iter().position_max_by_key(|x| x.abs()), None); + /// + /// let a = [-3_i32, 0, 1, 5, -10]; + /// assert_eq!(a.iter().position_max_by_key(|x| x.abs()), Some(4)); + /// + /// let a = [1_i32, 1, -1, -1]; + /// assert_eq!(a.iter().position_max_by_key(|x| x.abs()), Some(3)); + /// ``` + fn position_max_by_key<K, F>(self, mut key: F) -> Option<usize> + where Self: Sized, K: Ord, F: FnMut(&Self::Item) -> K + { + self.enumerate() + .max_by(|x, y| Ord::cmp(&key(&x.1), &key(&y.1))) + .map(|x| x.0) + } + + /// Return the position of the maximum element in the iterator, as + /// determined by the specified comparison function. + /// + /// If several elements are equally maximum, the position of the + /// last of them is returned. + /// + /// # Examples + /// + /// ``` + /// use itertools::Itertools; + /// + /// let a: [i32; 0] = []; + /// assert_eq!(a.iter().position_max_by(|x, y| x.cmp(y)), None); + /// + /// let a = [-3_i32, 0, 1, 5, -10]; + /// assert_eq!(a.iter().position_max_by(|x, y| x.cmp(y)), Some(3)); + /// + /// let a = [1_i32, 1, -1, -1]; + /// assert_eq!(a.iter().position_max_by(|x, y| x.cmp(y)), Some(1)); + /// ``` + fn position_max_by<F>(self, mut compare: F) -> Option<usize> + where Self: Sized, F: FnMut(&Self::Item, &Self::Item) -> Ordering + { + self.enumerate() + .max_by(|x, y| compare(&x.1, &y.1)) + .map(|x| x.0) + } + + /// Return the position of the minimum element in the iterator. + /// + /// If several elements are equally minimum, the position of the + /// first of them is returned. + /// + /// # Examples + /// + /// ``` + /// use itertools::Itertools; + /// + /// let a: [i32; 0] = []; + /// assert_eq!(a.iter().position_min(), None); + /// + /// let a = [-3, 0, 1, 5, -10]; + /// assert_eq!(a.iter().position_min(), Some(4)); + /// + /// let a = [1, 1, -1, -1]; + /// assert_eq!(a.iter().position_min(), Some(2)); + /// ``` + fn position_min(self) -> Option<usize> + where Self: Sized, Self::Item: Ord + { + self.enumerate() + .min_by(|x, y| Ord::cmp(&x.1, &y.1)) + .map(|x| x.0) + } + + /// Return the position of the minimum element in the iterator, as + /// determined by the specified function. + /// + /// If several elements are equally minimum, the position of the + /// first of them is returned. + /// + /// # Examples + /// + /// ``` + /// use itertools::Itertools; + /// + /// let a: [i32; 0] = []; + /// assert_eq!(a.iter().position_min_by_key(|x| x.abs()), None); + /// + /// let a = [-3_i32, 0, 1, 5, -10]; + /// assert_eq!(a.iter().position_min_by_key(|x| x.abs()), Some(1)); + /// + /// let a = [1_i32, 1, -1, -1]; + /// assert_eq!(a.iter().position_min_by_key(|x| x.abs()), Some(0)); + /// ``` + fn position_min_by_key<K, F>(self, mut key: F) -> Option<usize> + where Self: Sized, K: Ord, F: FnMut(&Self::Item) -> K + { + self.enumerate() + .min_by(|x, y| Ord::cmp(&key(&x.1), &key(&y.1))) + .map(|x| x.0) + } + + /// Return the position of the minimum element in the iterator, as + /// determined by the specified comparison function. + /// + /// If several elements are equally minimum, the position of the + /// first of them is returned. + /// + /// # Examples + /// + /// ``` + /// use itertools::Itertools; + /// + /// let a: [i32; 0] = []; + /// assert_eq!(a.iter().position_min_by(|x, y| x.cmp(y)), None); + /// + /// let a = [-3_i32, 0, 1, 5, -10]; + /// assert_eq!(a.iter().position_min_by(|x, y| x.cmp(y)), Some(4)); + /// + /// let a = [1_i32, 1, -1, -1]; + /// assert_eq!(a.iter().position_min_by(|x, y| x.cmp(y)), Some(2)); + /// ``` + fn position_min_by<F>(self, mut compare: F) -> Option<usize> + where Self: Sized, F: FnMut(&Self::Item, &Self::Item) -> Ordering + { + self.enumerate() + .min_by(|x, y| compare(&x.1, &y.1)) + .map(|x| x.0) + } + + /// Return the positions of the minimum and maximum elements in + /// the iterator. + /// + /// The return type [`MinMaxResult`] is an enum of three variants: + /// + /// - `NoElements` if the iterator is empty. + /// - `OneElement(xpos)` if the iterator has exactly one element. + /// - `MinMax(xpos, ypos)` is returned otherwise, where the + /// element at `xpos` ≤ the element at `ypos`. While the + /// referenced elements themselves may be equal, `xpos` cannot + /// be equal to `ypos`. + /// + /// On an iterator of length `n`, `position_minmax` does `1.5 * n` + /// comparisons, and so is faster than calling `position_min` and + /// `position_max` separately which does `2 * n` comparisons. + /// + /// For the minimum, if several elements are equally minimum, the + /// position of the first of them is returned. For the maximum, if + /// several elements are equally maximum, the position of the last + /// of them is returned. + /// + /// The elements can be floats but no particular result is + /// guaranteed if an element is NaN. + /// + /// # Examples + /// + /// ``` + /// use itertools::Itertools; + /// use itertools::MinMaxResult::{NoElements, OneElement, MinMax}; + /// + /// let a: [i32; 0] = []; + /// assert_eq!(a.iter().position_minmax(), NoElements); + /// + /// let a = [10]; + /// assert_eq!(a.iter().position_minmax(), OneElement(0)); + /// + /// let a = [-3, 0, 1, 5, -10]; + /// assert_eq!(a.iter().position_minmax(), MinMax(4, 3)); + /// + /// let a = [1, 1, -1, -1]; + /// assert_eq!(a.iter().position_minmax(), MinMax(2, 1)); + /// ``` + fn position_minmax(self) -> MinMaxResult<usize> + where Self: Sized, Self::Item: PartialOrd + { + use crate::MinMaxResult::{NoElements, OneElement, MinMax}; + match minmax::minmax_impl(self.enumerate(), |_| (), |x, y, _, _| x.1 < y.1) { + NoElements => NoElements, + OneElement(x) => OneElement(x.0), + MinMax(x, y) => MinMax(x.0, y.0), + } + } + + /// Return the postions of the minimum and maximum elements of an + /// iterator, as determined by the specified function. + /// + /// The return value is a variant of [`MinMaxResult`] like for + /// [`position_minmax`]. + /// + /// For the minimum, if several elements are equally minimum, the + /// position of the first of them is returned. For the maximum, if + /// several elements are equally maximum, the position of the last + /// of them is returned. + /// + /// The keys can be floats but no particular result is guaranteed + /// if a key is NaN. + /// + /// # Examples + /// + /// ``` + /// use itertools::Itertools; + /// use itertools::MinMaxResult::{NoElements, OneElement, MinMax}; + /// + /// let a: [i32; 0] = []; + /// assert_eq!(a.iter().position_minmax_by_key(|x| x.abs()), NoElements); + /// + /// let a = [10_i32]; + /// assert_eq!(a.iter().position_minmax_by_key(|x| x.abs()), OneElement(0)); + /// + /// let a = [-3_i32, 0, 1, 5, -10]; + /// assert_eq!(a.iter().position_minmax_by_key(|x| x.abs()), MinMax(1, 4)); + /// + /// let a = [1_i32, 1, -1, -1]; + /// assert_eq!(a.iter().position_minmax_by_key(|x| x.abs()), MinMax(0, 3)); + /// ``` + /// + /// [`position_minmax`]: Self::position_minmax + fn position_minmax_by_key<K, F>(self, mut key: F) -> MinMaxResult<usize> + where Self: Sized, K: PartialOrd, F: FnMut(&Self::Item) -> K + { + use crate::MinMaxResult::{NoElements, OneElement, MinMax}; + match self.enumerate().minmax_by_key(|e| key(&e.1)) { + NoElements => NoElements, + OneElement(x) => OneElement(x.0), + MinMax(x, y) => MinMax(x.0, y.0), + } + } + + /// Return the postions of the minimum and maximum elements of an + /// iterator, as determined by the specified comparison function. + /// + /// The return value is a variant of [`MinMaxResult`] like for + /// [`position_minmax`]. + /// + /// For the minimum, if several elements are equally minimum, the + /// position of the first of them is returned. For the maximum, if + /// several elements are equally maximum, the position of the last + /// of them is returned. + /// + /// # Examples + /// + /// ``` + /// use itertools::Itertools; + /// use itertools::MinMaxResult::{NoElements, OneElement, MinMax}; + /// + /// let a: [i32; 0] = []; + /// assert_eq!(a.iter().position_minmax_by(|x, y| x.cmp(y)), NoElements); + /// + /// let a = [10_i32]; + /// assert_eq!(a.iter().position_minmax_by(|x, y| x.cmp(y)), OneElement(0)); + /// + /// let a = [-3_i32, 0, 1, 5, -10]; + /// assert_eq!(a.iter().position_minmax_by(|x, y| x.cmp(y)), MinMax(4, 3)); + /// + /// let a = [1_i32, 1, -1, -1]; + /// assert_eq!(a.iter().position_minmax_by(|x, y| x.cmp(y)), MinMax(2, 1)); + /// ``` + /// + /// [`position_minmax`]: Self::position_minmax + fn position_minmax_by<F>(self, mut compare: F) -> MinMaxResult<usize> + where Self: Sized, F: FnMut(&Self::Item, &Self::Item) -> Ordering + { + use crate::MinMaxResult::{NoElements, OneElement, MinMax}; + match self.enumerate().minmax_by(|x, y| compare(&x.1, &y.1)) { + NoElements => NoElements, + OneElement(x) => OneElement(x.0), + MinMax(x, y) => MinMax(x.0, y.0), + } + } + + /// If the iterator yields exactly one element, that element will be returned, otherwise + /// an error will be returned containing an iterator that has the same output as the input + /// iterator. + /// + /// This provides an additional layer of validation over just calling `Iterator::next()`. + /// If your assumption that there should only be one element yielded is false this provides + /// the opportunity to detect and handle that, preventing errors at a distance. + /// + /// # Examples + /// ``` + /// use itertools::Itertools; + /// + /// assert_eq!((0..10).filter(|&x| x == 2).exactly_one().unwrap(), 2); + /// assert!((0..10).filter(|&x| x > 1 && x < 4).exactly_one().unwrap_err().eq(2..4)); + /// assert!((0..10).filter(|&x| x > 1 && x < 5).exactly_one().unwrap_err().eq(2..5)); + /// assert!((0..10).filter(|&_| false).exactly_one().unwrap_err().eq(0..0)); + /// ``` + fn exactly_one(mut self) -> Result<Self::Item, ExactlyOneError<Self>> + where + Self: Sized, + { + match self.next() { + Some(first) => { + match self.next() { + Some(second) => { + Err(ExactlyOneError::new(Some(Either::Left([first, second])), self)) + } + None => { + Ok(first) + } + } + } + None => Err(ExactlyOneError::new(None, self)), + } + } + + /// If the iterator yields no elements, Ok(None) will be returned. If the iterator yields + /// exactly one element, that element will be returned, otherwise an error will be returned + /// containing an iterator that has the same output as the input iterator. + /// + /// This provides an additional layer of validation over just calling `Iterator::next()`. + /// If your assumption that there should be at most one element yielded is false this provides + /// the opportunity to detect and handle that, preventing errors at a distance. + /// + /// # Examples + /// ``` + /// use itertools::Itertools; + /// + /// assert_eq!((0..10).filter(|&x| x == 2).at_most_one().unwrap(), Some(2)); + /// assert!((0..10).filter(|&x| x > 1 && x < 4).at_most_one().unwrap_err().eq(2..4)); + /// assert!((0..10).filter(|&x| x > 1 && x < 5).at_most_one().unwrap_err().eq(2..5)); + /// assert_eq!((0..10).filter(|&_| false).at_most_one().unwrap(), None); + /// ``` + fn at_most_one(mut self) -> Result<Option<Self::Item>, ExactlyOneError<Self>> + where + Self: Sized, + { + match self.next() { + Some(first) => { + match self.next() { + Some(second) => { + Err(ExactlyOneError::new(Some(Either::Left([first, second])), self)) + } + None => { + Ok(Some(first)) + } + } + } + None => Ok(None), + } + } + + /// An iterator adaptor that allows the user to peek at multiple `.next()` + /// values without advancing the base iterator. + /// + /// # Examples + /// ``` + /// use itertools::Itertools; + /// + /// let mut iter = (0..10).multipeek(); + /// assert_eq!(iter.peek(), Some(&0)); + /// assert_eq!(iter.peek(), Some(&1)); + /// assert_eq!(iter.peek(), Some(&2)); + /// assert_eq!(iter.next(), Some(0)); + /// assert_eq!(iter.peek(), Some(&1)); + /// ``` + #[cfg(feature = "use_alloc")] + fn multipeek(self) -> MultiPeek<Self> + where + Self: Sized, + { + multipeek_impl::multipeek(self) + } + + /// Collect the items in this iterator and return a `HashMap` which + /// contains each item that appears in the iterator and the number + /// of times it appears. + /// + /// # Examples + /// ``` + /// # use itertools::Itertools; + /// let counts = [1, 1, 1, 3, 3, 5].into_iter().counts(); + /// assert_eq!(counts[&1], 3); + /// assert_eq!(counts[&3], 2); + /// assert_eq!(counts[&5], 1); + /// assert_eq!(counts.get(&0), None); + /// ``` + #[cfg(feature = "use_std")] + fn counts(self) -> HashMap<Self::Item, usize> + where + Self: Sized, + Self::Item: Eq + Hash, + { + let mut counts = HashMap::new(); + self.for_each(|item| *counts.entry(item).or_default() += 1); + counts + } + + /// Collect the items in this iterator and return a `HashMap` which + /// contains each item that appears in the iterator and the number + /// of times it appears, + /// determining identity using a keying function. + /// + /// ``` + /// # use itertools::Itertools; + /// struct Character { + /// first_name: &'static str, + /// last_name: &'static str, + /// } + /// + /// let characters = + /// vec![ + /// Character { first_name: "Amy", last_name: "Pond" }, + /// Character { first_name: "Amy", last_name: "Wong" }, + /// Character { first_name: "Amy", last_name: "Santiago" }, + /// Character { first_name: "James", last_name: "Bond" }, + /// Character { first_name: "James", last_name: "Sullivan" }, + /// Character { first_name: "James", last_name: "Norington" }, + /// Character { first_name: "James", last_name: "Kirk" }, + /// ]; + /// + /// let first_name_frequency = + /// characters + /// .into_iter() + /// .counts_by(|c| c.first_name); + /// + /// assert_eq!(first_name_frequency["Amy"], 3); + /// assert_eq!(first_name_frequency["James"], 4); + /// assert_eq!(first_name_frequency.contains_key("Asha"), false); + /// ``` + #[cfg(feature = "use_std")] + fn counts_by<K, F>(self, f: F) -> HashMap<K, usize> + where + Self: Sized, + K: Eq + Hash, + F: FnMut(Self::Item) -> K, + { + self.map(f).counts() + } + + /// Converts an iterator of tuples into a tuple of containers. + /// + /// `unzip()` consumes an entire iterator of n-ary tuples, producing `n` collections, one for each + /// column. + /// + /// This function is, in some sense, the opposite of [`multizip`]. + /// + /// ``` + /// use itertools::Itertools; + /// + /// let inputs = vec![(1, 2, 3), (4, 5, 6), (7, 8, 9)]; + /// + /// let (a, b, c): (Vec<_>, Vec<_>, Vec<_>) = inputs + /// .into_iter() + /// .multiunzip(); + /// + /// assert_eq!(a, vec![1, 4, 7]); + /// assert_eq!(b, vec![2, 5, 8]); + /// assert_eq!(c, vec![3, 6, 9]); + /// ``` + fn multiunzip<FromI>(self) -> FromI + where + Self: Sized + MultiUnzip<FromI>, + { + MultiUnzip::multiunzip(self) + } +} + +impl<T: ?Sized> Itertools for T where T: Iterator { } + +/// Return `true` if both iterables produce equal sequences +/// (elements pairwise equal and sequences of the same length), +/// `false` otherwise. +/// +/// [`IntoIterator`] enabled version of [`Iterator::eq`]. +/// +/// ``` +/// assert!(itertools::equal(vec![1, 2, 3], 1..4)); +/// assert!(!itertools::equal(&[0, 0], &[0, 0, 0])); +/// ``` +pub fn equal<I, J>(a: I, b: J) -> bool + where I: IntoIterator, + J: IntoIterator, + I::Item: PartialEq<J::Item> +{ + a.into_iter().eq(b) +} + +/// Assert that two iterables produce equal sequences, with the same +/// semantics as [`equal(a, b)`](equal). +/// +/// **Panics** on assertion failure with a message that shows the +/// two iteration elements. +/// +/// ```ignore +/// assert_equal("exceed".split('c'), "excess".split('c')); +/// // ^PANIC: panicked at 'Failed assertion Some("eed") == Some("ess") for iteration 1', +/// ``` +pub fn assert_equal<I, J>(a: I, b: J) + where I: IntoIterator, + J: IntoIterator, + I::Item: fmt::Debug + PartialEq<J::Item>, + J::Item: fmt::Debug, +{ + let mut ia = a.into_iter(); + let mut ib = b.into_iter(); + let mut i = 0; + loop { + match (ia.next(), ib.next()) { + (None, None) => return, + (a, b) => { + let equal = match (&a, &b) { + (&Some(ref a), &Some(ref b)) => a == b, + _ => false, + }; + assert!(equal, "Failed assertion {a:?} == {b:?} for iteration {i}", + i=i, a=a, b=b); + i += 1; + } + } + } +} + +/// Partition a sequence using predicate `pred` so that elements +/// that map to `true` are placed before elements which map to `false`. +/// +/// The order within the partitions is arbitrary. +/// +/// Return the index of the split point. +/// +/// ``` +/// use itertools::partition; +/// +/// # // use repeated numbers to not promise any ordering +/// let mut data = [7, 1, 1, 7, 1, 1, 7]; +/// let split_index = partition(&mut data, |elt| *elt >= 3); +/// +/// assert_eq!(data, [7, 7, 7, 1, 1, 1, 1]); +/// assert_eq!(split_index, 3); +/// ``` +pub fn partition<'a, A: 'a, I, F>(iter: I, mut pred: F) -> usize + where I: IntoIterator<Item = &'a mut A>, + I::IntoIter: DoubleEndedIterator, + F: FnMut(&A) -> bool +{ + let mut split_index = 0; + let mut iter = iter.into_iter(); + 'main: while let Some(front) = iter.next() { + if !pred(front) { + loop { + match iter.next_back() { + Some(back) => if pred(back) { + std::mem::swap(front, back); + break; + }, + None => break 'main, + } + } + } + split_index += 1; + } + split_index +} + +/// An enum used for controlling the execution of `fold_while`. +/// +/// See [`.fold_while()`](Itertools::fold_while) for more information. +#[derive(Copy, Clone, Debug, Eq, PartialEq)] +pub enum FoldWhile<T> { + /// Continue folding with this value + Continue(T), + /// Fold is complete and will return this value + Done(T), +} + +impl<T> FoldWhile<T> { + /// Return the value in the continue or done. + pub fn into_inner(self) -> T { + match self { + FoldWhile::Continue(x) | FoldWhile::Done(x) => x, + } + } + + /// Return true if `self` is `Done`, false if it is `Continue`. + pub fn is_done(&self) -> bool { + match *self { + FoldWhile::Continue(_) => false, + FoldWhile::Done(_) => true, + } + } +} |