#![warn(missing_docs)]
#![crate_name="itertools"]
//! Itertools — extra iterator adaptors, functions and macros.
//!
//! To use the iterator methods in this crate, import the [`Itertools` trait](./trait.Itertools.html):
//!
//! ```ignore
//! use itertools::Itertools;
//! ```
//!
//! To enable the macros in this crate, use the `#[macro_use]` attribute:
//!
//! ```ignore
//! #[macro_use] extern crate itertools;
//! ```
//!
//! ## Rust Version
//!
//! This version of itertools requires Rust 1.12 or later.
//!
#![doc(html_root_url="https://docs.rs/itertools/")]
extern crate either;
pub use either::Either;
use std::iter::{IntoIterator};
use std::fmt::Write;
use std::cmp::Ordering;
use std::fmt;
use std::hash::Hash;
#[macro_use]
mod impl_macros;
/// The concrete iterator types.
pub mod structs {
pub use adaptors::{
Dedup,
Interleave,
InterleaveShortest,
Product,
PutBack,
PutBackN,
Batching,
Step,
MapResults,
Merge,
MergeBy,
MultiPeek,
TakeWhileRef,
WhileSome,
Coalesce,
TupleCombinations,
Combinations,
Unique,
UniqueBy,
Flatten,
};
pub use cons_tuples_impl::ConsTuples;
pub use format::{Format, FormatWith};
pub use groupbylazy::{IntoChunks, Chunk, Chunks, GroupBy, Group, Groups};
pub use intersperse::Intersperse;
pub use kmerge_impl::{KMerge, KMergeBy};
pub use pad_tail::PadUsing;
pub use peeking_take_while::PeekingTakeWhile;
pub use rciter_impl::RcIter;
pub use repeatn::RepeatN;
pub use sources::{RepeatCall, Unfold, Iterate};
pub use tee::Tee;
pub use tuple_impl::{TupleBuffer, TupleWindows, Tuples};
pub use with_position::WithPosition;
pub use zip_eq_impl::ZipEq;
pub use zip_longest::ZipLongest;
pub use ziptuple::Zip;
}
pub use structs::*;
pub use cons_tuples_impl::cons_tuples;
pub use diff::diff_with;
pub use diff::Diff;
pub use kmerge_impl::{kmerge_by};
pub use minmax::MinMaxResult;
pub use peeking_take_while::PeekingNext;
pub use repeatn::repeat_n;
pub use sources::{repeat_call, unfold, iterate};
pub use with_position::Position;
pub use zip_longest::EitherOrBoth;
pub use ziptuple::multizip;
mod adaptors;
#[doc(hidden)]
pub mod free;
#[doc(inline)]
pub use free::*;
mod cons_tuples_impl;
mod diff;
mod format;
mod groupbylazy;
mod intersperse;
mod kmerge_impl;
mod minmax;
mod pad_tail;
mod peeking_take_while;
mod rciter_impl;
mod repeatn;
mod size_hint;
mod sources;
mod tee;
mod tuple_impl;
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.
///
/// ```
/// #[macro_use] extern crate itertools;
/// # 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,)*) => (
iproduct!(@flatten $crate::cons_tuples(iproduct!($I, $J)), $($K,)*)
);
($I:expr) => (
(::std::iter::IntoIterator::into_iter($I))
);
($I:expr, $J:expr) => (
$crate::Itertools::cartesian_product(iproduct!($I), iproduct!($J))
);
($I:expr, $J:expr, $($K:expr),+) => (
iproduct!(@flatten iproduct!($I, $J), $($K,)+)
);
}
#[macro_export]
/// Create an iterator running multiple iterators in lockstep.
///
/// The izip! iterator yields elements until any subiterator
/// returns `None`.
///
/// Iterator element type is like `(A, B, ..., E)` if formed
/// from iterators `(I, J, ..., M)` implementing `I: Iterator<A>`,
/// `J: Iterator<B>`, ..., `M: Iterator<E>`
///
/// ```
/// #[macro_use] extern crate itertools;
/// # fn main() {
///
/// // Iterate over three sequences side-by-side
/// let mut xs = [0, 0, 0];
/// let ys = [69, 107, 101];
///
/// for (i, a, b) in izip!(0..100, &mut xs, &ys) {
/// *a = i ^ *b;
/// }
///
/// assert_eq!(xs, [69, 106, 103]);
/// # }
/// ```
macro_rules! izip {
($I:expr) => (
(::std::iter::IntoIterator::into_iter($I))
);
($($I:expr),*) => (
{
$crate::multizip(($(izip!($I)),*))
}
);
}
/// The trait `Itertools`: extra iterator adaptors and methods for iterators.
///
/// 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()`](#method.interleave)
///
/// * *Regular methods* are those that don't return iterators and instead
/// return a regular value of some other kind.
/// [`.next_tuple()`](#method.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
/// run out.
///
/// Iterator element type is `Self::Item`.
///
/// This iterator is *fused*.
///
/// ```
/// use itertools::Itertools;
///
/// let it = (0..3).interleave(vec![7, 8]);
/// itertools::assert_equal(it, vec![0, 7, 1, 8, 2]);
/// ```
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 one of them runs out.
///
/// Iterator element type is `Self::Item`.
///
/// ```
/// use itertools::Itertools;
///
/// let it = (0..5).interleave_shortest(vec![7, 8]);
/// itertools::assert_equal(it, vec![0, 7, 1, 8, 2]);
/// ```
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)
}
/// Create an iterator which iterates over both this and the specified
/// iterator simultaneously, yielding pairs of two optional elements.
///
/// This iterator is *fused*.
///
/// When both iterators return `None`, all further invocations of `.next()`
/// will return `None`.
///
/// Iterator element type is
/// [`EitherOrBoth<Self::Item, J::Item>`](enum.EitherOrBoth.html).
///
/// ```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 recives 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 up in pairs
/// let pit = (0..4).batching(|mut 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.
/// for (key, group) in &data.into_iter().group_by(|elt| *elt >= 0) {
/// // Check that the sum of each group is +/- 4.
/// assert_eq!(4, group.sum::<i32>().abs());
/// }
/// ```
fn group_by<K, F>(self, key: F) -> GroupBy<K, Self, F>
where Self: Sized,
F: FnMut(&Self::Item) -> K,
{
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());
/// }
/// ```
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 4).
///
/// `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).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: tuple_impl::TupleCollect,
T::Item: Clone
{
tuple_impl::tuple_windows(self)
}
/// Return an iterator that groups the items in tuples of a specific size
/// (up to 4).
///
/// See also the method [`.next_tuple()`](#method.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`](structs/struct.Tuples.html#method.into_buffer).
fn tuples<T>(self) -> Tuples<Self, T>
where Self: Sized + Iterator<Item = T::Item>,
T: tuple_impl::TupleCollect
{
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. It 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);
/// ```
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]);
/// ```
fn step(self, n: usize) -> Step<Self>
where Self: Sized
{
adaptors::step(self, n)
}
/// 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_results(|i| i + 1);
/// itertools::assert_equal(it, vec![Ok(42), Err(false), Ok(12)]);
/// ```
fn map_results<F, T, U, E>(self, f: F) -> MapResults<Self, F>
where Self: Iterator<Item = Result<T, E>> + Sized,
F: FnMut(T) -> U,
{
adaptors::map_results(self, f)
}
/// Return an iterator adaptor that merges the two base iterators in
/// ascending order. If both base iterators are sorted (ascending), the
/// result is sorted.
///
/// Iterator element type is `Self::Item`.
///
/// ```
/// use itertools::Itertools;
///
/// let a = (0..11).step(3);
/// let b = (0..11).step(5);
/// let it = a.merge(b);
/// itertools::assert_equal(it, vec![0, 0, 3, 5, 6, 9, 10]);
/// ```
fn merge<J>(self, other: J) -> Merge<Self, J::IntoIter>
where Self: Sized,
Self::Item: PartialOrd,
J: IntoIterator<Item = Self::Item>
{
merge(self, other)
}
/// Return an iterator adaptor that merges the two base iterators in order.
/// This is much like `.merge()` but allows for a custom ordering.
///
/// This can be especially useful for sequences of tuples.
///
/// Iterator element type is `Self::Item`.
///
/// ```
/// use itertools::Itertools;
///
/// let a = (0..).zip("bc".chars());
/// let b = (0..).zip("ad".chars());
/// let it = a.merge_by(b, |x, y| x.1 <= y.1);
/// itertools::assert_equal(it, vec![(0, 'a'), (0, 'b'), (1, 'c'), (1, 'd')]);
/// ```
fn merge_by<J, F>(self, other: J, is_first: F) -> MergeBy<Self, J::IntoIter, F>
where Self: Sized,
J: IntoIterator<Item = Self::Item>,
F: FnMut(&Self::Item, &Self::Item) -> bool
{
adaptors::merge_by_new(self, other.into_iter(), is_first)
}
/// Return an iterator adaptor that flattens an iterator of iterators by
/// merging them in ascending order.
///
/// If all base iterators are sorted (ascending), the result is sorted.
///
/// Iterator element type is `Self::Item`.
///
/// ```
/// use itertools::Itertools;
///
/// let a = (0..6).step(3);
/// let b = (1..6).step(3);
/// let c = (2..6).step(3);
/// let it = vec![a, b, c].into_iter().kmerge();
/// itertools::assert_equal(it, vec![0, 1, 2, 3, 4, 5]);
/// ```
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.));
/// ```
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 uses the passed-in closure to
/// optionally merge together consecutive elements.
///
/// The closure `f` is passed two elements, `x`, `y` and may return either
/// (1) `Ok(z)` to merge the two values or (2) `Err((x', y'))` to indicate
/// they can't be merged. In (2), the value `x'` is emitted by the iterator.
/// Coalesce continues with either `z` (1) or `y'` (2), and the next
/// iterator element as the next pair of elements to merge.
///
/// 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)
}
/// 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.
///
/// ```
/// 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]);
/// ```
fn unique(self) -> Unique<Self>
where Self: Sized,
Self::Item: Clone + Eq + Hash
{
adaptors::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.
///
/// ```
/// 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"]);
/// ```
fn unique_by<V, F>(self, f: F) -> UniqueBy<Self, V, F>
where Self: Sized,
V: Eq + Hash,
F: FnMut(&Self::Item) -> V
{
adaptors::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()`](#method.take_while_ref)
/// which is a similar adaptor.
fn peeking_take_while<F>(&mut self, accept: F) -> PeekingTakeWhile<Self, F>
where Self: Sized + PeekingNext,
F: FnMut(&Self::Item) -> bool,
{
peeking_take_while::peeking_take_while(self, accept)
}
/// Return an iterator adaptor that borrows from a `Clone`-able iterator
/// to only pick off elements while the predicate `accept` returns `true`.
///
/// It uses the `Clone` trait to restore the original iterator so that the
/// last and rejected element (first `false`) is still available when
/// `take_while_ref` is done.
///
/// ```
/// use itertools::Itertools;
///
/// let mut hexadecimals = "0123456789abcdef".chars();
///
/// let decimals = hexadecimals.take_while_ref(|c| c.is_numeric())
/// .collect::<String>();
/// assert_eq!(decimals, "0123456789");
/// assert_eq!(hexadecimals.next(), Some('a'));
///
/// ```
fn take_while_ref<F>(&mut self, accept: F) -> TakeWhileRef<Self, F>
where Self: Clone,
F: FnMut(&Self::Item) -> bool
{
adaptors::take_while_ref(self, accept)
}
/// Return an iterator adaptor that filters `Option<A>` iterator elements
/// and produces `A`. Stops on the first `None` encountered.
///
/// Iterator element type is `A`, the unwrapped element.
///
/// ```
/// use itertools::Itertools;
///
/// // List all hexadecimal digits
/// itertools::assert_equal(
/// (0..).map(|i| std::char::from_digit(i, 16)).while_some(),
/// "0123456789abcdef".chars());
///
/// ```
fn while_some<A>(self) -> WhileSome<Self>
where Self: Sized + Iterator<Item = Option<A>>
{
adaptors::while_some(self)
}
/// Return an iterator adaptor that iterates over the combinations of the
/// elements from an iterator.
///
/// Iterator element can be any homogeneous tuple of type `Self::Item` with
/// size up to 4.
///
/// ```
/// use itertools::Itertools;
///
/// let mut v = Vec::new();
/// for (a, b) in (1..5).tuple_combinations() {
/// v.push((a, b));
/// }
/// assert_eq!(v, vec![(1, 2), (1, 3), (1, 4), (2, 3), (2, 4), (3, 4)]);
///
/// let mut it = (1..5).tuple_combinations();
/// assert_eq!(Some((1, 2, 3)), it.next());
/// assert_eq!(Some((1, 2, 4)), it.next());
/// assert_eq!(Some((1, 3, 4)), it.next());
/// assert_eq!(Some((2, 3, 4)), it.next());
/// assert_eq!(None, it.next());
///
/// // this requires a type hint
/// let it = (1..5).tuple_combinations::<(_, _, _)>();
/// itertools::assert_equal(it, vec![(1, 2, 3), (1, 2, 4), (1, 3, 4), (2, 3, 4)]);
///
/// // you can also specify the complete type
/// use itertools::TupleCombinations;
/// use std::ops::Range;
///
/// let it: TupleCombinations<Range<u32>, (u32, u32, u32)> = (1..5).tuple_combinations();
/// itertools::assert_equal(it, vec![(1, 2, 3), (1, 2, 4), (1, 3, 4), (2, 3, 4)]);
/// ```
fn tuple_combinations<T>(self) -> TupleCombinations<Self, T>
where Self: Sized + Clone,
Self::Item: Clone,
T: adaptors::HasCombination<Self>,
{
adaptors::tuple_combinations(self)
}
/// Return an iterator adaptor that iterates over the `n`-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],
/// ]);
/// ```
fn combinations(self, n: usize) -> Combinations<Self>
where Self: Sized,
Self::Item: Clone
{
adaptors::combinations(self, n)
}
/// 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)
}
/// Unravel a nested iterator.
///
/// This is more or less equivalent to `.flat_map` with an identity
/// function.
///
/// ```
/// use itertools::Itertools;
///
/// let data = vec![vec![1, 2, 3], vec![4, 5, 6]];
/// let flattened = data.iter().flatten();
///
/// itertools::assert_equal(flattened, &[1, 2, 3, 4, 5, 6]);
/// ```
fn flatten(self) -> Flatten<Self, <Self::Item as IntoIterator>::IntoIter>
where Self: Sized,
Self::Item: IntoIterator
{
adaptors::flatten(self)
}
/// Return an iterator adaptor that wraps each element in a `Position` to
/// ease special-case handling of the first or last elements.
///
/// Iterator element type is
/// [`Position<Self::Item>`](enum.Position.html)
///
/// ```
/// 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)
}
// non-adaptor methods
/// Advances the iterator and returns the next items grouped in a tuple of
/// a specific size (up to 4).
///
/// 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: tuple_impl::TupleCollect
{
T::collect_from_iter_no_buf(self)
}
/// 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
{
let mut index = 0usize;
for elt in self {
if pred(&elt) {
return Some((index, elt));
}
index += 1;
}
None
}
/// Consume the first `n` elements from the iterator eagerly,
/// and return the same iterator again.
///
/// It works similarly to *.skip(* `n` *)* except it is eager and
/// preserves the iterator type.
///
/// ```
/// use itertools::Itertools;
///
/// let mut iter = "αβγ".chars().dropping(2);
/// itertools::assert_equal(iter, "γ".chars());
/// ```
///
/// *Fusing notes: if the iterator is exhausted by dropping,
/// the result of calling `.next()` again depends on the iterator implementation.*
fn dropping(mut self, n: usize) -> Self
where Self: Sized
{
if n > 0 {
self.nth(n - 1);
}
self
}
/// Consume the last `n` elements from the iterator eagerly,
/// and return the same iterator again.
///
/// This is only possible on double ended iterators. `n` may be
/// larger than the number of elements.
///
/// Note: This method is eager, dropping the back elements immediately and
/// preserves the iterator type.
///
/// ```
/// use itertools::Itertools;
///
/// let init = vec![0, 3, 6, 9].into_iter().dropping_back(1);
/// itertools::assert_equal(init, vec![0, 3, 6]);
/// ```
fn dropping_back(mut self, n: usize) -> Self
where Self: Sized,
Self: DoubleEndedIterator
{
if n > 0 {
(&mut self).rev().nth(n - 1);
}
self
}
/// Run the closure `f` eagerly on each element of the iterator.
///
/// Consumes the iterator until its end.
///
/// ```
/// use std::sync::mpsc::channel;
/// use itertools::Itertools;
///
/// let (tx, rx) = channel();
///
/// // use .foreach() to apply a function to each value -- sending it
/// (0..5).map(|x| x * 2 + 1).foreach(|x| { tx.send(x).unwrap(); } );
///
/// drop(tx);
///
/// itertools::assert_equal(rx.iter(), vec![1, 3, 5, 7, 9]);
/// ```
fn foreach<F>(self, mut f: F)
where F: FnMut(Self::Item),
Self: Sized,
{
self.fold((), move |(), element| f(element))
}
/// `.collect_vec()` is simply a type specialization of `.collect()`,
/// for convenience.
fn collect_vec(self) -> Vec<Self::Item>
where Self: Sized
{
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, seperated 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");
/// ```
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();
for elt in self {
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()`.
///
/// 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 FnMut(&fmt::Display) -> fmt::Result) -> fmt::Result,
{
format::new_format(self, sep, format)
}
/// Fold `Result` values from an iterator.
///
/// Only `Ok` values are folded. If no error is encountered, the folded
/// value is returned inside `Ok`. Otherwise, the operation terminates
/// and returns the first `Err` value it encounters. No iterator elements are
/// consumed after the first error.
///
/// The first accumulator value is the `start` parameter.
/// Each iteration passes the accumulator value and the next value inside `Ok`
/// to the fold function `f` and its return value becomes the new accumulator value.
///
/// For example the sequence *Ok(1), Ok(2), Ok(3)* will result in a
/// computation like this:
///
/// ```ignore
/// let mut accum = start;
/// accum = f(accum, 1);
/// accum = f(accum, 2);
/// accum = f(accum, 3);
/// ```
///
/// With a `start` value of 0 and an addition as folding function,
/// this effetively 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_results(0, Add::add),
/// Ok(3)
/// );
/// assert!(
/// values.iter()
/// .map(|&x| if x >= 0 { Ok(x) } else { Err("Negative number") })
/// .fold_results(0, Add::add)
/// .is_err()
/// );
/// ```
fn fold_results<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_results`.
///
/// ```
/// 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);
/// ```
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))
}
/// An iterator method that applies a function, producing a single, final value.
///
/// `fold_while()` is basically equivalent to `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>
{
let mut acc = init;
while let Some(item) = self.next() {
match f(acc, item) {
FoldWhile::Continue(res) => acc = res,
res @ FoldWhile::Done(_) => return res,
}
}
FoldWhile::Continue(acc)
}
/// Collect all iterator elements into a sorted vector in ascending order.
///
/// **Note:** This consumes the entire iterator, uses the
/// `slice::sort_by()` method and returns the sorted vector.
///
/// ```
/// use itertools::Itertools;
///
/// // sort the letters of the text in ascending order
/// let text = "bdacfe";
/// itertools::assert_equal(text.chars().sorted(),
/// "abcdef".chars());
/// ```
fn sorted(self) -> Vec<Self::Item>
where Self: Sized,
Self::Item: Ord
{
self.sorted_by(Ord::cmp)
}
/// Collect all iterator elements into a sorted vector.
///
/// **Note:** This consumes the entire iterator, uses the
/// `slice::sort_by()` method and returns the sorted vector.
///
/// ```
/// use itertools::Itertools;
///
/// // sort people in descending order by age
/// let people = vec![("Jane", 20), ("John", 18), ("Jill", 30), ("Jack", 27)];
///
/// let oldest_people_first = people
/// .into_iter()
/// .sorted_by(|a, b| Ord::cmp(&b.1, &a.1))
/// .into_iter()
/// .map(|(person, _age)| person);
///
/// itertools::assert_equal(oldest_people_first,
/// vec!["Jill", "Jack", "Jane", "John"]);
/// ```
fn sorted_by<F>(self, cmp: F) -> Vec<Self::Item>
where Self: Sized,
F: FnMut(&Self::Item, &Self::Item) -> Ordering,
{
let mut v: Vec<Self::Item> = self.collect();
v.sort_by(cmp);
v
}
/// 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, predicate: F) -> (A, B)
where Self: Sized,
F: Fn(Self::Item) -> Either<L, R>,
A: Default + Extend<L>,
B: Default + Extend<R>,
{
let mut left = A::default();
let mut right = B::default();
for val in self {
match predicate(val) {
Either::Left(v) => left.extend(Some(v)),
Either::Right(v) => right.extend(Some(v)),
}
}
(left, right)
}
/// 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()`.
///
/// 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()`.
///
/// 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)
)
}
}
impl<T: ?Sized> Itertools for T where T: Iterator { }
/// Return `true` if both iterators produce equal sequences
/// (elements pairwise equal and sequences of the same length),
/// `false` otherwise.
///
/// **Note:** the standard library method `Iterator::eq` now provides
/// the same functionality.
///
/// ```
/// 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>
{
let mut ia = a.into_iter();
let mut ib = b.into_iter();
loop {
match ia.next() {
Some(ref x) => match ib.next() {
Some(ref y) => if x != y { return false; },
None => return false,
},
None => return ib.next().is_none()
}
}
}
/// Assert that two iterators produce equal sequences, with the same
/// semantics as *equal(a, b)*.
///
/// **Panics** on assertion failure with a message that shows the
/// two iteration elements.
///
/// ```ignore
/// assert_equal("exceed".split('c'), "excess".split('c'));
/// // ^PANIC: panicked at 'Failed assertion Some("eed") == Some("ess") for iteration 1',
/// ```
pub fn assert_equal<I, J>(a: I, b: J)
where I: IntoIterator,
J: IntoIterator,
I::Item: fmt::Debug + PartialEq<J::Item>,
J::Item: fmt::Debug,
{
let mut ia = a.into_iter();
let mut ib = b.into_iter();
let mut i = 0;
loop {
match (ia.next(), ib.next()) {
(None, None) => return,
(a, b) => {
let equal = match (&a, &b) {
(&Some(ref a), &Some(ref b)) => a == b,
_ => false,
};
assert!(equal, "Failed assertion {a:?} == {b:?} for iteration {i}",
i=i, a=a, b=b);
i += 1;
}
}
}
}
/// Partition a sequence using predicate `pred` so that elements
/// that map to `true` are placed before elements which map to `false`.
///
/// The order within the partitions is arbitrary.
///
/// Return the index of the split point.
///
/// ```
/// use itertools::partition;
///
/// # // use repeated numbers to not promise any ordering
/// let mut data = [7, 1, 1, 7, 1, 1, 7];
/// let split_index = partition(&mut data, |elt| *elt >= 3);
///
/// assert_eq!(data, [7, 7, 7, 1, 1, 1, 1]);
/// assert_eq!(split_index, 3);
/// ```
pub fn partition<'a, A: 'a, I, F>(iter: I, mut pred: F) -> usize
where I: IntoIterator<Item = &'a mut A>,
I::IntoIter: DoubleEndedIterator,
F: FnMut(&A) -> bool
{
let mut split_index = 0;
let mut iter = iter.into_iter();
'main: while let Some(front) = iter.next() {
if !pred(front) {
loop {
match iter.next_back() {
Some(back) => if pred(back) {
std::mem::swap(front, back);
break;
},
None => break 'main,
}
}
}
split_index += 1;
}
split_index
}
/// An enum used for controlling the execution of `.fold_while()`.
///
/// See [`.fold_while()`](trait.Itertools.html#method.fold_while) for more information.
#[derive(Copy, Clone, Debug)]
pub enum FoldWhile<T> {
/// Continue folding with this value
Continue(T),
/// Fold is complete and will return this value
Done(T),
}
impl<T> FoldWhile<T> {
/// Return the value in the continue or done.
pub fn into_inner(self) -> T {
match self {
FoldWhile::Continue(x) | FoldWhile::Done(x) => x,
}
}
/// Return true if `self` is `Done`, false if it is `Continue`.
pub fn is_done(&self) -> bool {
match *self {
FoldWhile::Continue(_) => false,
FoldWhile::Done(_) => true,
}
}
}