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#![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 1.43.1 or later.
#[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;
use std::cmp::Ordering;
#[cfg(feature = "use_std")]
use std::collections::HashMap;
#[cfg(feature = "use_std")]
use std::collections::HashSet;
use std::fmt;
#[cfg(feature = "use_alloc")]
use std::fmt::Write;
#[cfg(feature = "use_std")]
use std::hash::Hash;
use std::iter::{once, IntoIterator};
#[cfg(feature = "use_alloc")]
type VecIntoIter<T> = alloc::vec::IntoIter<T>;
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 {
#[cfg(feature = "use_alloc")]
pub use crate::adaptors::MultiProduct;
pub use crate::adaptors::{
Batching, Coalesce, Dedup, DedupBy, DedupByWithCount, DedupWithCount, FilterMapOk,
FilterOk, Interleave, InterleaveShortest, MapInto, MapOk, Positions, Product, PutBack,
TakeWhileRef, TupleCombinations, Update, WhileSome,
};
#[allow(deprecated)]
pub use crate::adaptors::{MapResults, Step};
#[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;
#[cfg(feature = "use_std")]
pub use crate::duplicates_impl::{Duplicates, DuplicatesBy};
pub use crate::exactly_one_err::ExactlyOneError;
pub use crate::flatten_ok::FlattenOk;
pub use crate::format::{Format, FormatWith};
#[cfg(feature = "use_alloc")]
pub use crate::groupbylazy::{Chunk, Chunks, Group, GroupBy, Groups, IntoChunks};
#[cfg(feature = "use_std")]
pub use crate::grouping_map::{GroupingMap, GroupingMapBy};
pub use crate::intersperse::{Intersperse, IntersperseWith};
#[cfg(feature = "use_alloc")]
pub use crate::kmerge_impl::{KMerge, KMergeBy};
pub use crate::merge_join::{Merge, MergeBy, MergeJoinBy};
#[cfg(feature = "use_alloc")]
pub use crate::multipeek_impl::MultiPeek;
pub use crate::pad_tail::PadUsing;
#[cfg(feature = "use_alloc")]
pub use crate::peek_nth::PeekNth;
pub use crate::peeking_take_while::PeekingTakeWhile;
#[cfg(feature = "use_alloc")]
pub use crate::permutations::Permutations;
#[cfg(feature = "use_alloc")]
pub use crate::powerset::Powerset;
pub use crate::process_results_impl::ProcessResults;
#[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::{Iterate, RepeatCall, Unfold};
pub use crate::take_while_inclusive::TakeWhileInclusive;
#[cfg(feature = "use_alloc")]
pub use crate::tee::Tee;
pub use crate::tuple_impl::{CircularTupleWindows, TupleBuffer, TupleWindows, Tuples};
#[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;
}
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::{iterate, repeat_call, unfold};
#[allow(deprecated)]
pub use crate::structs::*;
pub use crate::unziptuple::{multiunzip, MultiUnzip};
pub use crate::with_position::Position;
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::*;
#[cfg(feature = "use_alloc")]
mod combinations;
#[cfg(feature = "use_alloc")]
mod combinations_with_replacement;
mod concat_impl;
mod cons_tuples_impl;
mod diff;
#[cfg(feature = "use_std")]
mod duplicates_impl;
mod exactly_one_err;
#[cfg(feature = "use_alloc")]
mod extrema_set;
mod flatten_ok;
mod format;
#[cfg(feature = "use_alloc")]
mod group_map;
#[cfg(feature = "use_alloc")]
mod groupbylazy;
#[cfg(feature = "use_std")]
mod grouping_map;
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;
mod take_while_inclusive;
#[cfg(feature = "use_alloc")]
mod tee;
mod tuple_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)
}
/// “Lift” a function of the values of the current iterator so as to process
/// an iterator of `Result` values instead.
///
/// `processor` is a closure that receives an adapted version of the iterator
/// as the only argument — the adapted iterator produces elements of type `T`,
/// as long as the original iterator produces `Ok` values.
///
/// If the original iterable produces an error at any point, the adapted
/// iterator ends and it will return the error iself.
///
/// Otherwise, the return value from the closure is returned wrapped
/// inside `Ok`.
///
/// # Example
///
/// ```
/// use itertools::Itertools;
///
/// type Item = Result<i32, &'static str>;
///
/// let first_values: Vec<Item> = vec![Ok(1), Ok(0), Ok(3)];
/// let second_values: Vec<Item> = vec![Ok(2), Ok(1), Err("overflow")];
///
/// // “Lift” the iterator .max() method to work on the Ok-values.
/// let first_max = first_values.into_iter().process_results(|iter| iter.max().unwrap_or(0));
/// let second_max = second_values.into_iter().process_results(|iter| iter.max().unwrap_or(0));
///
/// assert_eq!(first_max, Ok(3));
/// assert!(second_max.is_err());
/// ```
fn process_results<F, T, E, R>(self, processor: F) -> Result<R, E>
where
Self: Iterator<Item = Result<T, E>> + Sized,
F: FnOnce(ProcessResults<Self, E>) -> R,
{
process_results(self, processor)
}
/// 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_by(3);
/// let b = (0..11).step_by(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,
{
merge_join::merge_by_new(self, other, is_first)
}
/// Create an iterator that merges items from both this and the specified
/// iterator in ascending order.
///
/// The function can either return an `Ordering` variant or a boolean.
///
/// If `cmp_fn` returns `Ordering`,
/// 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 a = vec![0, 2, 4, 6, 1].into_iter();
/// let b = (0..10).step_by(3);
///
/// itertools::assert_equal(
/// a.merge_join_by(b, |i, j| i.cmp(j)),
/// vec![Both(0, 0), Left(2), Right(3), Left(4), Both(6, 6), Left(1), Right(9)]
/// );
/// ```
///
/// If `cmp_fn` returns `bool`,
/// it chooses whether to pair elements based on the boolean returned by the
/// specified 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 `Either::Left(i)` when `true`,
/// and remove `i` from its source iterator
/// - Emit `Either::Right(j)` when `false`,
/// and remove `j` from its source iterator
///
/// It is similar to the `Ordering` case if the first argument is considered
/// "less" than the second argument.
///
/// ```
/// use itertools::Itertools;
/// use itertools::Either::{Left, Right};
///
/// let a = vec![0, 2, 4, 6, 1].into_iter();
/// let b = (0..10).step_by(3);
///
/// itertools::assert_equal(
/// a.merge_join_by(b, |i, j| i <= j),
/// vec![Left(0), Right(0), Left(2), Right(3), Left(4), Left(6), Left(1), Right(6), Right(9)]
/// );
/// ```
#[inline]
fn merge_join_by<J, F, T>(self, other: J, cmp_fn: F) -> MergeJoinBy<Self, J::IntoIter, F>
where
J: IntoIterator,
F: FnMut(&Self::Item, &J::Item) -> T,
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_by(3);
/// let b = (1..6).step_by(3);
/// let c = (2..6).step_by(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)
}
/// Returns an iterator adaptor that consumes elements while the given
/// predicate is `true`, *including* the element for which the predicate
/// first returned `false`.
///
/// The [`.take_while()`][std::iter::Iterator::take_while] adaptor is useful
/// when you want items satisfying a predicate, but to know when to stop
/// taking elements, we have to consume that first element that doesn't
/// satisfy the predicate. This adaptor includes that element where
/// [`.take_while()`][std::iter::Iterator::take_while] would drop it.
///
/// The [`.take_while_ref()`][crate::Itertools::take_while_ref] adaptor
/// serves a similar purpose, but this adaptor doesn't require [`Clone`]ing
/// the underlying elements.
///
/// ```rust
/// # use itertools::Itertools;
/// let items = vec![1, 2, 3, 4, 5];
/// let filtered: Vec<_> = items
/// .into_iter()
/// .take_while_inclusive(|&n| n % 3 != 0)
/// .collect();
///
/// assert_eq!(filtered, vec![1, 2, 3]);
/// ```
///
/// ```rust
/// # use itertools::Itertools;
/// let items = vec![1, 2, 3, 4, 5];
///
/// let take_while_inclusive_result: Vec<_> = items
/// .iter()
/// .copied()
/// .take_while_inclusive(|&n| n % 3 != 0)
/// .collect();
/// let take_while_result: Vec<_> = items
/// .into_iter()
/// .take_while(|&n| n % 3 != 0)
/// .collect();
///
/// assert_eq!(take_while_inclusive_result, vec![1, 2, 3]);
/// assert_eq!(take_while_result, vec![1, 2]);
/// // both iterators have the same items remaining at this point---the 3
/// // is lost from the `take_while` vec
/// ```
///
/// ```rust
/// # use itertools::Itertools;
/// #[derive(Debug, PartialEq)]
/// struct NoCloneImpl(i32);
///
/// let non_clonable_items: Vec<_> = vec![1, 2, 3, 4, 5]
/// .into_iter()
/// .map(NoCloneImpl)
/// .collect();
/// let filtered: Vec<_> = non_clonable_items
/// .into_iter()
/// .take_while_inclusive(|n| n.0 % 3 != 0)
/// .collect();
/// let expected: Vec<_> = vec![1, 2, 3].into_iter().map(NoCloneImpl).collect();
/// assert_eq!(filtered, expected);
fn take_while_inclusive<F>(self, accept: F) -> TakeWhileInclusive<Self, F>
where
Self: Sized,
F: FnMut(&Self::Item) -> bool,
{
take_while_inclusive::TakeWhileInclusive::new(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)]);
/// ```
///
/// # Guarantees
///
/// If the adapted iterator is deterministic,
/// this iterator adapter yields items in a reliable order.
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],
/// ]);
/// ```
///
/// # Guarantees
///
/// If the adapted iterator is deterministic,
/// this iterator adapter yields items in a reliable order.
#[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.
///
/// If you are looking for permutations with replacements,
/// use `repeat_n(iter, k).multi_cartesian_product()` instead.
///
/// ```
/// 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 combines each element with 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,
{
self.enumerate().find(|(_, elt)| pred(elt))
}
/// 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),
}
}
/// If there are elements and they are all equal, return a single copy of that element.
/// If there are no elements, return an Error containing None.
/// If there are elements and they are not all equal, return a tuple containing the first
/// two non-equal elements found.
///
/// ```
/// use itertools::Itertools;
///
/// let data = vec![1, 1, 1, 2, 2, 3, 3, 3, 4, 5, 5];
/// assert_eq!(data.iter().all_equal_value(), Err(Some((&1, &2))));
/// assert_eq!(data[0..3].iter().all_equal_value(), Ok(&1));
/// assert_eq!(data[3..5].iter().all_equal_value(), Ok(&2));
/// assert_eq!(data[5..8].iter().all_equal_value(), Ok(&3));
///
/// let data : Option<usize> = None;
/// assert_eq!(data.into_iter().all_equal_value(), Err(None));
/// ```
#[allow(clippy::type_complexity)]
fn all_equal_value(&mut self) -> Result<Self::Item, Option<(Self::Item, Self::Item)>>
where
Self: Sized,
Self::Item: PartialEq,
{
let first = self.next().ok_or(None)?;
let other = self.find(|x| x != &first);
if let Some(other) = other {
Err(Some((first, other)))
} else {
Ok(first)
}
}
/// 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 + 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(())
/// }
/// ```
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:
///
/// ```no_run
/// # let start = 0;
/// # let f = |x, y| x + y;
/// 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 you should also decide carefully:
///
/// - if `f` is a trivial operation like `u32::wrapping_add`, prefer the normal
/// [`Iterator::reduce`] instead since it will most likely result in the generation of simpler
/// code because the compiler is able to optimize it
/// - otherwise if `f` is non-trivial like `format!`, you should use `tree_fold1` since it
/// reduces the number of operations from `O(n)` to `O(ln(n))`
///
/// Here "non-trivial" means:
///
/// - any allocating operation
/// - any function that is a composition of many operations
///
/// ```
/// 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::{Err as Break, Ok as Continue};
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.
///
/// This sort is unstable (i.e., may reorder equal 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.
///
/// This sort is unstable (i.e., may reorder equal 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.
///
/// This sort is unstable (i.e., may reorder equal 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.
///
/// This sort is stable (i.e., does not reorder equal 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.
///
/// This sort is stable (i.e., does not reorder equal 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", 30)];
///
/// 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.
///
/// This sort is stable (i.e., does not reorder equal 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", 30)];
///
/// 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.
///
/// This sort is stable (i.e., does not reorder equal 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", 30)];
///
/// 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_alloc")]
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_alloc")]
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_alloc")]
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_alloc")]
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_alloc")]
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 maximum 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_alloc")]
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::{MinMax, NoElements, OneElement};
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::{MinMax, NoElements, OneElement};
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::{MinMax, NoElements, OneElement};
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)
}
/// Returns the length of the iterator if one exists.
/// Otherwise return `self.size_hint()`.
///
/// Fallible [`ExactSizeIterator::len`].
///
/// Inherits guarantees and restrictions from [`Iterator::size_hint`].
///
/// ```
/// use itertools::Itertools;
///
/// assert_eq!([0; 10].iter().try_len(), Ok(10));
/// assert_eq!((10..15).try_len(), Ok(5));
/// assert_eq!((15..10).try_len(), Ok(0));
/// assert_eq!((10..).try_len(), Err((usize::MAX, None)));
/// assert_eq!((10..15).filter(|x| x % 2 == 0).try_len(), Err((0, Some(5))));
/// ```
fn try_len(&self) -> Result<usize, size_hint::SizeHint> {
let sh = self.size_hint();
match sh {
(lo, Some(hi)) if lo == hi => Ok(lo),
_ => Err(sh),
}
}
}
impl<T> Itertools for T where T: Iterator + ?Sized {}
/// 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.
///
/// ```should_panic
/// # use itertools::assert_equal;
/// 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(a), Some(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();
while let Some(front) = iter.next() {
if !pred(front) {
match iter.rfind(|back| pred(back)) {
Some(back) => std::mem::swap(front, back),
None => break,
}
}
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 {
Self::Continue(x) | Self::Done(x) => x,
}
}
/// Return true if `self` is `Done`, false if it is `Continue`.
pub fn is_done(&self) -> bool {
match *self {
Self::Continue(_) => false,
Self::Done(_) => true,
}
}
}