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263fdfeea8
rust/src/libcore/iter.rs
Corey Farwell 263fdfeea8 Cleanup and modernize some things in libcore::iter
2015-04-03 21:38:51 -07:00

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// Copyright 2013-2014 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
//! Composable external iterators
//!
//! # The `Iterator` trait
//!
//! This module defines Rust's core iteration trait. The `Iterator` trait has
//! one unimplemented method, `next`. All other methods are derived through
//! default methods to perform operations such as `zip`, `chain`, `enumerate`,
//! and `fold`.
//!
//! The goal of this module is to unify iteration across all containers in Rust.
//! An iterator can be considered as a state machine which is used to track
//! which element will be yielded next.
//!
//! There are various extensions also defined in this module to assist with
//! various types of iteration, such as the `DoubleEndedIterator` for iterating
//! in reverse, the `FromIterator` trait for creating a container from an
//! iterator, and much more.
//!
//! # Rust's `for` loop
//!
//! The special syntax used by rust's `for` loop is based around the
//! `IntoIterator` trait defined in this module. `for` loops can be viewed as a
//! syntactical expansion into a `loop`, for example, the `for` loop in this
//! example is essentially translated to the `loop` below.
//!
//! ```
//! let values = vec![1, 2, 3];
//!
//! for x in values {
//! println!("{}", x);
//! }
//!
//! // Rough translation of the iteration without a `for` iterator.
//! # let values = vec![1, 2, 3];
//! let mut it = values.into_iter();
//! loop {
//! match it.next() {
//! Some(x) => println!("{}", x),
//! None => break,
//! }
//! }
//! ```
//!
//! Because `Iterator`s implement `IntoIterator`, this `for` loop syntax can be applied to any
//! iterator over any type.
#![stable(feature = "rust1", since = "1.0.0")]
use self::MinMaxResult::*;
use clone::Clone;
use cmp;
use cmp::Ord;
use default::Default;
use marker;
use mem;
use num::{Int, Zero, One};
use ops::{self, Add, Sub, FnMut, RangeFrom};
use option::Option::{self, Some, None};
use marker::Sized;
use usize;
fn _assert_is_object_safe(_: &Iterator) {}
/// An interface for dealing with "external iterators". These types of iterators
/// can be resumed at any time as all state is stored internally as opposed to
/// being located on the call stack.
///
/// The Iterator protocol states that an iterator yields a (potentially-empty,
/// potentially-infinite) sequence of values, and returns `None` to signal that
/// it's finished. The Iterator protocol does not define behavior after `None`
/// is returned. A concrete Iterator implementation may choose to behave however
/// it wishes, either by returning `None` infinitely, or by doing something
/// else.
#[lang="iterator"]
#[stable(feature = "rust1", since = "1.0.0")]
#[rustc_on_unimplemented = "`{Self}` is not an iterator; maybe try calling \
`.iter()` or a similar method"]
pub trait Iterator {
/// The type of the elements being iterated
#[stable(feature = "rust1", since = "1.0.0")]
type Item;
/// Advance the iterator and return the next value. Return `None` when the
/// end is reached.
#[stable(feature = "rust1", since = "1.0.0")]
fn next(&mut self) -> Option<Self::Item>;
/// Returns a lower and upper bound on the remaining length of the iterator.
///
/// An upper bound of `None` means either there is no known upper bound, or
/// the upper bound does not fit within a `usize`.
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
fn size_hint(&self) -> (usize, Option<usize>) { (0, None) }
/// Counts the number of elements in this iterator.
///
/// # Examples
///
/// ```
/// let a = [1, 2, 3, 4, 5];
/// assert_eq!(a.iter().count(), 5);
/// ```
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
fn count(self) -> usize where Self: Sized {
self.fold(0, |cnt, _x| cnt + 1)
}
/// Loops through the entire iterator, returning the last element.
///
/// # Examples
///
/// ```
/// let a = [1, 2, 3, 4, 5];
/// assert!(a.iter().last().unwrap() == &5);
/// ```
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
fn last(self) -> Option<Self::Item> where Self: Sized {
let mut last = None;
for x in self { last = Some(x); }
last
}
/// Loops through `n` iterations, returning the `n`th element of the
/// iterator.
///
/// # Examples
///
/// ```
/// let a = [1, 2, 3, 4, 5];
/// let mut it = a.iter();
/// assert!(it.nth(2).unwrap() == &3);
/// assert!(it.nth(2) == None);
/// ```
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
fn nth(&mut self, mut n: usize) -> Option<Self::Item> where Self: Sized {
for x in self.by_ref() {
if n == 0 { return Some(x) }
n -= 1;
}
None
}
/// Chain this iterator with another, returning a new iterator that will
/// finish iterating over the current iterator, and then iterate
/// over the other specified iterator.
///
/// # Examples
///
/// ```
/// let a = [0];
/// let b = [1];
/// let mut it = a.iter().chain(b.iter());
/// assert_eq!(it.next().unwrap(), &0);
/// assert_eq!(it.next().unwrap(), &1);
/// assert!(it.next().is_none());
/// ```
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
fn chain<U>(self, other: U) -> Chain<Self, U> where
Self: Sized, U: Iterator<Item=Self::Item>,
{
Chain{a: self, b: other, flag: false}
}
/// Creates an iterator that iterates over both this and the specified
/// iterators simultaneously, yielding the two elements as pairs. When
/// either iterator returns None, all further invocations of next() will
/// return None.
///
/// # Examples
///
/// ```
/// let a = [0];
/// let b = [1];
/// let mut it = a.iter().zip(b.iter());
/// assert_eq!(it.next().unwrap(), (&0, &1));
/// assert!(it.next().is_none());
/// ```
///
/// `zip` can provide similar functionality to `enumerate`:
///
/// ```
/// for pair in "foo".chars().enumerate() {
/// println!("{:?}", pair);
/// }
///
/// for pair in (0..).zip("foo".chars()) {
/// println!("{:?}", pair);
/// }
/// ```
///
/// both produce the same output.
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
fn zip<U: Iterator>(self, other: U) -> Zip<Self, U> where Self: Sized {
Zip{a: self, b: other}
}
/// Creates a new iterator that will apply the specified function to each
/// element returned by the first, yielding the mapped element instead.
///
/// # Examples
///
/// ```
/// let a = [1, 2];
/// let mut it = a.iter().map(|&x| 2 * x);
/// assert_eq!(it.next().unwrap(), 2);
/// assert_eq!(it.next().unwrap(), 4);
/// assert!(it.next().is_none());
/// ```
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
fn map<B, F>(self, f: F) -> Map<Self, F> where
Self: Sized, F: FnMut(Self::Item) -> B,
{
Map{iter: self, f: f}
}
/// Creates an iterator that applies the predicate to each element returned
/// by this iterator. The only elements that will be yielded are those that
/// make the predicate evaluate to `true`.
///
/// # Examples
///
/// ```
/// let a = [1, 2];
/// let mut it = a.iter().filter(|&x| *x > 1);
/// assert_eq!(it.next().unwrap(), &2);
/// assert!(it.next().is_none());
/// ```
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
fn filter<P>(self, predicate: P) -> Filter<Self, P> where
Self: Sized, P: FnMut(&Self::Item) -> bool,
{
Filter{iter: self, predicate: predicate}
}
/// Creates an iterator that both filters and maps elements.
/// If the specified function returns None, the element is skipped.
/// Otherwise the option is unwrapped and the new value is yielded.
///
/// # Examples
///
/// ```
/// let a = [1, 2];
/// let mut it = a.iter().filter_map(|&x| if x > 1 {Some(2 * x)} else {None});
/// assert_eq!(it.next().unwrap(), 4);
/// assert!(it.next().is_none());
/// ```
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
fn filter_map<B, F>(self, f: F) -> FilterMap<Self, F> where
Self: Sized, F: FnMut(Self::Item) -> Option<B>,
{
FilterMap { iter: self, f: f }
}
/// Creates an iterator that yields a pair of the value returned by this
/// iterator plus the current index of iteration.
///
/// `enumerate` keeps its count as a `usize`. If you want to count by a
/// different sized integer, the `zip` function provides similar
/// functionality.
///
/// # Examples
///
/// ```
/// let a = [100, 200];
/// let mut it = a.iter().enumerate();
/// assert_eq!(it.next().unwrap(), (0, &100));
/// assert_eq!(it.next().unwrap(), (1, &200));
/// assert!(it.next().is_none());
/// ```
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
fn enumerate(self) -> Enumerate<Self> where Self: Sized {
Enumerate{iter: self, count: 0}
}
/// Creates an iterator that has a `.peek()` method
/// that returns an optional reference to the next element.
///
/// # Examples
///
/// ```
/// # #![feature(core)]
/// let xs = [100, 200, 300];
/// let mut it = xs.iter().cloned().peekable();
/// assert_eq!(*it.peek().unwrap(), 100);
/// assert_eq!(it.next().unwrap(), 100);
/// assert_eq!(it.next().unwrap(), 200);
/// assert_eq!(*it.peek().unwrap(), 300);
/// assert_eq!(*it.peek().unwrap(), 300);
/// assert_eq!(it.next().unwrap(), 300);
/// assert!(it.peek().is_none());
/// assert!(it.next().is_none());
/// ```
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
fn peekable(self) -> Peekable<Self> where Self: Sized {
Peekable{iter: self, peeked: None}
}
/// Creates an iterator that invokes the predicate on elements
/// until it returns false. Once the predicate returns false, that
/// element and all further elements are yielded.
///
/// # Examples
///
/// ```
/// let a = [1, 2, 3, 4, 5];
/// let mut it = a.iter().skip_while(|&a| *a < 3);
/// assert_eq!(it.next().unwrap(), &3);
/// assert_eq!(it.next().unwrap(), &4);
/// assert_eq!(it.next().unwrap(), &5);
/// assert!(it.next().is_none());
/// ```
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
fn skip_while<P>(self, predicate: P) -> SkipWhile<Self, P> where
Self: Sized, P: FnMut(&Self::Item) -> bool,
{
SkipWhile{iter: self, flag: false, predicate: predicate}
}
/// Creates an iterator that yields elements so long as the predicate
/// returns true. After the predicate returns false for the first time, no
/// further elements will be yielded.
///
/// # Examples
///
/// ```
/// let a = [1, 2, 3, 4, 5];
/// let mut it = a.iter().take_while(|&a| *a < 3);
/// assert_eq!(it.next().unwrap(), &1);
/// assert_eq!(it.next().unwrap(), &2);
/// assert!(it.next().is_none());
/// ```
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
fn take_while<P>(self, predicate: P) -> TakeWhile<Self, P> where
Self: Sized, P: FnMut(&Self::Item) -> bool,
{
TakeWhile{iter: self, flag: false, predicate: predicate}
}
/// Creates an iterator that skips the first `n` elements of this iterator,
/// and then yields all further items.
///
/// # Examples
///
/// ```
/// let a = [1, 2, 3, 4, 5];
/// let mut it = a.iter().skip(3);
/// assert_eq!(it.next().unwrap(), &4);
/// assert_eq!(it.next().unwrap(), &5);
/// assert!(it.next().is_none());
/// ```
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
fn skip(self, n: usize) -> Skip<Self> where Self: Sized {
Skip{iter: self, n: n}
}
/// Creates an iterator that yields the first `n` elements of this
/// iterator.
///
/// # Examples
///
/// ```
/// let a = [1, 2, 3, 4, 5];
/// let mut it = a.iter().take(3);
/// assert_eq!(it.next().unwrap(), &1);
/// assert_eq!(it.next().unwrap(), &2);
/// assert_eq!(it.next().unwrap(), &3);
/// assert!(it.next().is_none());
/// ```
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
fn take(self, n: usize) -> Take<Self> where Self: Sized, {
Take{iter: self, n: n}
}
/// Creates a new iterator that behaves in a similar fashion to fold.
/// There is a state which is passed between each iteration and can be
/// mutated as necessary. The yielded values from the closure are yielded
/// from the Scan instance when not None.
///
/// # Examples
///
/// ```
/// let a = [1, 2, 3, 4, 5];
/// let mut it = a.iter().scan(1, |fac, &x| {
/// *fac = *fac * x;
/// Some(*fac)
/// });
/// assert_eq!(it.next().unwrap(), 1);
/// assert_eq!(it.next().unwrap(), 2);
/// assert_eq!(it.next().unwrap(), 6);
/// assert_eq!(it.next().unwrap(), 24);
/// assert_eq!(it.next().unwrap(), 120);
/// assert!(it.next().is_none());
/// ```
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
fn scan<St, B, F>(self, initial_state: St, f: F) -> Scan<Self, St, F>
where Self: Sized, F: FnMut(&mut St, Self::Item) -> Option<B>,
{
Scan{iter: self, f: f, state: initial_state}
}
/// Creates an iterator that maps each element to an iterator,
/// and yields the elements of the produced iterators.
///
/// # Examples
///
/// ```
/// # #![feature(core)]
/// let xs = [2, 3];
/// let ys = [0, 1, 0, 1, 2];
/// let it = xs.iter().flat_map(|&x| (0..).take(x));
/// // Check that `it` has the same elements as `ys`
/// for (i, x) in it.enumerate() {
/// assert_eq!(x, ys[i]);
/// }
/// ```
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
fn flat_map<U, F>(self, f: F) -> FlatMap<Self, U, F>
where Self: Sized, U: Iterator, F: FnMut(Self::Item) -> U,
{
FlatMap{iter: self, f: f, frontiter: None, backiter: None }
}
/// Creates an iterator that yields `None` forever after the underlying
/// iterator yields `None`. Random-access iterator behavior is not
/// affected, only single and double-ended iterator behavior.
///
/// # Examples
///
/// ```
/// fn process<U: Iterator<Item=i32>>(it: U) -> i32 {
/// let mut it = it.fuse();
/// let mut sum = 0;
/// for x in it.by_ref() {
/// if x > 5 {
/// break;
/// }
/// sum += x;
/// }
/// // did we exhaust the iterator?
/// if it.next().is_none() {
/// sum += 1000;
/// }
/// sum
/// }
/// let x = vec![1, 2, 3, 7, 8, 9];
/// assert_eq!(process(x.into_iter()), 6);
/// let x = vec![1, 2, 3];
/// assert_eq!(process(x.into_iter()), 1006);
/// ```
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
fn fuse(self) -> Fuse<Self> where Self: Sized {
Fuse{iter: self, done: false}
}
/// Creates an iterator that calls a function with a reference to each
/// element before yielding it. This is often useful for debugging an
/// iterator pipeline.
///
/// # Examples
///
/// ```
/// # #![feature(core)]
/// use std::iter::AdditiveIterator;
///
/// let a = [1, 4, 2, 3, 8, 9, 6];
/// let sum = a.iter()
/// .map(|x| *x)
/// .inspect(|&x| println!("filtering {}", x))
/// .filter(|&x| x % 2 == 0)
/// .inspect(|&x| println!("{} made it through", x))
/// .sum();
/// println!("{}", sum);
/// ```
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
fn inspect<F>(self, f: F) -> Inspect<Self, F> where
Self: Sized, F: FnMut(&Self::Item),
{
Inspect{iter: self, f: f}
}
/// Creates a wrapper around a mutable reference to the iterator.
///
/// This is useful to allow applying iterator adaptors while still
/// retaining ownership of the original iterator value.
///
/// # Examples
///
/// ```
/// let mut it = 0..10;
/// // sum the first five values
/// let partial_sum = it.by_ref().take(5).fold(0, |a, b| a + b);
/// assert!(partial_sum == 10);
/// assert!(it.next() == Some(5));
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
fn by_ref(&mut self) -> &mut Self where Self: Sized { self }
/// Loops through the entire iterator, collecting all of the elements into
/// a container implementing `FromIterator`.
///
/// # Examples
///
/// ```
/// let expected = [1, 2, 3, 4, 5];
/// let actual: Vec<_> = expected.iter().cloned().collect();
/// assert_eq!(actual, expected);
/// ```
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
fn collect<B: FromIterator<Self::Item>>(self) -> B where Self: Sized {
FromIterator::from_iter(self)
}
/// Loops through the entire iterator, collecting all of the elements into
/// one of two containers, depending on a predicate. The elements of the
/// first container satisfy the predicate, while the elements of the second
/// do not.
///
/// ```
/// # #![feature(core)]
/// let vec = vec![1, 2, 3, 4];
/// let (even, odd): (Vec<_>, Vec<_>) = vec.into_iter().partition(|&n| n % 2 == 0);
/// assert_eq!(even, [2, 4]);
/// assert_eq!(odd, [1, 3]);
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
fn partition<B, F>(self, mut f: F) -> (B, B) where
Self: Sized,
B: Default + Extend<Self::Item>,
F: FnMut(&Self::Item) -> bool
{
let mut left: B = Default::default();
let mut right: B = Default::default();
for x in self {
if f(&x) {
left.extend(Some(x).into_iter())
} else {
right.extend(Some(x).into_iter())
}
}
(left, right)
}
/// Performs a fold operation over the entire iterator, returning the
/// eventual state at the end of the iteration.
///
/// # Examples
///
/// ```
/// let a = [1, 2, 3, 4, 5];
/// assert!(a.iter().fold(0, |acc, &item| acc + item) == 15);
/// ```
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
fn fold<B, F>(self, init: B, mut f: F) -> B where
Self: Sized, F: FnMut(B, Self::Item) -> B,
{
let mut accum = init;
for x in self {
accum = f(accum, x);
}
accum
}
/// Tests whether the predicate holds true for all elements in the iterator.
///
/// # Examples
///
/// ```
/// let a = [1, 2, 3, 4, 5];
/// assert!(a.iter().all(|x| *x > 0));
/// assert!(!a.iter().all(|x| *x > 2));
/// ```
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
fn all<F>(&mut self, mut f: F) -> bool where
Self: Sized, F: FnMut(Self::Item) -> bool
{
for x in self.by_ref() {
if !f(x) {
return false;
}
}
true
}
/// Tests whether any element of an iterator satisfies the specified
/// predicate.
///
/// Does not consume the iterator past the first found element.
///
/// # Examples
///
/// ```
/// # #![feature(core)]
/// let a = [1, 2, 3, 4, 5];
/// let mut it = a.iter();
/// assert!(it.any(|x| *x == 3));
/// assert_eq!(&it[..], [4, 5]);
///
/// ```
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
fn any<F>(&mut self, mut f: F) -> bool where
Self: Sized,
F: FnMut(Self::Item) -> bool
{
for x in self.by_ref() {
if f(x) {
return true;
}
}
false
}
/// Returns the first element satisfying the specified predicate.
///
/// Does not consume the iterator past the first found element.
///
/// # Examples
///
/// ```
/// # #![feature(core)]
/// let a = [1, 2, 3, 4, 5];
/// let mut it = a.iter();
/// assert_eq!(it.find(|&x| *x == 3).unwrap(), &3);
/// assert_eq!(&it[..], [4, 5]);
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
fn find<P>(&mut self, mut predicate: P) -> Option<Self::Item> where
Self: Sized,
P: FnMut(&Self::Item) -> bool,
{
for x in self.by_ref() {
if predicate(&x) { return Some(x) }
}
None
}
/// Return the index of the first element satisfying the specified predicate
///
/// Does not consume the iterator past the first found element.
///
/// # Examples
///
/// ```
/// # #![feature(core)]
/// let a = [1, 2, 3, 4, 5];
/// let mut it = a.iter();
/// assert_eq!(it.position(|x| *x == 3).unwrap(), 2);
/// assert_eq!(&it[..], [4, 5]);
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
fn position<P>(&mut self, mut predicate: P) -> Option<usize> where
Self: Sized,
P: FnMut(Self::Item) -> bool,
{
let mut i = 0;
for x in self.by_ref() {
if predicate(x) {
return Some(i);
}
i += 1;
}
None
}
/// Return the index of the last element satisfying the specified predicate
///
/// If no element matches, None is returned.
///
/// Does not consume the iterator *before* the first found element.
///
/// # Examples
///
/// ```
/// # #![feature(core)]
/// let a = [1, 2, 2, 4, 5];
/// let mut it = a.iter();
/// assert_eq!(it.rposition(|x| *x == 2).unwrap(), 2);
/// assert_eq!(&it[..], [1, 2]);
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
fn rposition<P>(&mut self, mut predicate: P) -> Option<usize> where
P: FnMut(Self::Item) -> bool,
Self: Sized + ExactSizeIterator + DoubleEndedIterator
{
let mut i = self.len();
while let Some(v) = self.next_back() {
if predicate(v) {
return Some(i - 1);
}
i -= 1;
}
None
}
/// Consumes the entire iterator to return the maximum element.
///
/// Returns the rightmost element if the comparison determines two elements
/// to be equally maximum.
///
/// # Examples
///
/// ```
/// let a = [1, 2, 3, 4, 5];
/// assert!(a.iter().max().unwrap() == &5);
/// ```
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
fn max(self) -> Option<Self::Item> where Self: Sized, Self::Item: Ord
{
self.fold(None, |max, y| {
match max {
None => Some(y),
Some(x) => Some(cmp::max(x, y))
}
})
}
/// Consumes the entire iterator to return the minimum element.
///
/// Returns the leftmost element if the comparison determines two elements
/// to be equally minimum.
///
/// # Examples
///
/// ```
/// let a = [1, 2, 3, 4, 5];
/// assert!(a.iter().min().unwrap() == &1);
/// ```
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
fn min(self) -> Option<Self::Item> where Self: Sized, Self::Item: Ord
{
self.fold(None, |min, y| {
match min {
None => Some(y),
Some(x) => Some(cmp::min(x, y))
}
})
}
/// `min_max` finds 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`, `min_max` does `1.5 * n` comparisons,
/// and so is faster than calling `min` and `max` separately which does `2 *
/// n` comparisons.
///
/// # Examples
///
/// ```
/// # #![feature(core)]
/// use std::iter::MinMaxResult::{NoElements, OneElement, MinMax};
///
/// let a: [i32; 0] = [];
/// assert_eq!(a.iter().min_max(), NoElements);
///
/// let a = [1];
/// assert!(a.iter().min_max() == OneElement(&1));
///
/// let a = [1, 2, 3, 4, 5];
/// assert!(a.iter().min_max() == MinMax(&1, &5));
///
/// let a = [1, 1, 1, 1];
/// assert!(a.iter().min_max() == MinMax(&1, &1));
/// ```
#[unstable(feature = "core", reason = "return type may change")]
fn min_max(mut self) -> MinMaxResult<Self::Item> where Self: Sized, Self::Item: Ord
{
let (mut min, mut max) = match self.next() {
None => return NoElements,
Some(x) => {
match self.next() {
None => return OneElement(x),
Some(y) => if x <= y {(x, y)} else {(y, x)}
}
}
};
loop {
// `first` and `second` are the two next elements we want to look
// at. We first compare `first` and `second` (#1). The smaller one
// is then compared to current minimum (#2). The larger one is
// compared to current maximum (#3). This way we do 3 comparisons
// for 2 elements.
let first = match self.next() {
None => break,
Some(x) => x
};
let second = match self.next() {
None => {
if first < min {
min = first;
} else if first >= max {
max = first;
}
break;
}
Some(x) => x
};
if first <= second {
if first < min { min = first }
if second >= max { max = second }
} else {
if second < min { min = second }
if first >= max { max = first }
}
}
MinMax(min, max)
}
/// Return the element that gives the maximum value from the
/// specified function.
///
/// Returns the rightmost element if the comparison determines two elements
/// to be equally maximum.
///
/// # Examples
///
/// ```
/// # #![feature(core)]
///
/// let a = [-3_i32, 0, 1, 5, -10];
/// assert_eq!(*a.iter().max_by(|x| x.abs()).unwrap(), -10);
/// ```
#[inline]
#[unstable(feature = "core",
reason = "may want to produce an Ordering directly; see #15311")]
fn max_by<B: Ord, F>(self, mut f: F) -> Option<Self::Item> where
Self: Sized,
F: FnMut(&Self::Item) -> B,
{
self.fold(None, |max: Option<(Self::Item, B)>, y| {
let y_val = f(&y);
match max {
None => Some((y, y_val)),
Some((x, x_val)) => if y_val >= x_val {
Some((y, y_val))
} else {
Some((x, x_val))
}
}
}).map(|(x, _)| x)
}
/// Return the element that gives the minimum value from the
/// specified function.
///
/// Returns the leftmost element if the comparison determines two elements
/// to be equally minimum.
///
/// # Examples
///
/// ```
/// # #![feature(core)]
///
/// let a = [-3_i32, 0, 1, 5, -10];
/// assert_eq!(*a.iter().min_by(|x| x.abs()).unwrap(), 0);
/// ```
#[inline]
#[unstable(feature = "core",
reason = "may want to produce an Ordering directly; see #15311")]
fn min_by<B: Ord, F>(self, mut f: F) -> Option<Self::Item> where
Self: Sized,
F: FnMut(&Self::Item) -> B,
{
self.fold(None, |min: Option<(Self::Item, B)>, y| {
let y_val = f(&y);
match min {
None => Some((y, y_val)),
Some((x, x_val)) => if x_val <= y_val {
Some((x, x_val))
} else {
Some((y, y_val))
}
}
}).map(|(x, _)| x)
}
/// Change the direction of the iterator
///
/// The flipped iterator swaps the ends on an iterator that can already
/// be iterated from the front and from the back.
///
///
/// If the iterator also implements RandomAccessIterator, the flipped
/// iterator is also random access, with the indices starting at the back
/// of the original iterator.
///
/// Note: Random access with flipped indices still only applies to the first
/// `std::usize::MAX` elements of the original iterator.
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
fn rev(self) -> Rev<Self> where Self: Sized {
Rev{iter: self}
}
/// Converts an iterator of pairs into a pair of containers.
///
/// Loops through the entire iterator, collecting the first component of
/// each item into one new container, and the second component into another.
///
/// # Examples
///
/// ```
/// # #![feature(core)]
/// let a = [(1, 2), (3, 4)];
/// let (left, right): (Vec<_>, Vec<_>) = a.iter().cloned().unzip();
/// assert_eq!(left, [1, 3]);
/// assert_eq!(right, [2, 4]);
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
fn unzip<A, B, FromA, FromB>(self) -> (FromA, FromB) where
FromA: Default + Extend<A>,
FromB: Default + Extend<B>,
Self: Sized + Iterator<Item=(A, B)>,
{
struct SizeHint<A>(usize, Option<usize>, marker::PhantomData<A>);
impl<A> Iterator for SizeHint<A> {
type Item = A;
fn next(&mut self) -> Option<A> { None }
fn size_hint(&self) -> (usize, Option<usize>) {
(self.0, self.1)
}
}
let (lo, hi) = self.size_hint();
let mut ts: FromA = Default::default();
let mut us: FromB = Default::default();
ts.extend(SizeHint(lo, hi, marker::PhantomData));
us.extend(SizeHint(lo, hi, marker::PhantomData));
for (t, u) in self {
ts.extend(Some(t).into_iter());
us.extend(Some(u).into_iter());
}
(ts, us)
}
/// Creates an iterator that clones the elements it yields. Useful for
/// converting an Iterator<&T> to an Iterator<T>.
#[stable(feature = "rust1", since = "1.0.0")]
fn cloned<'a, T: 'a>(self) -> Cloned<Self>
where Self: Sized + Iterator<Item=&'a T>, T: Clone
{
Cloned { it: self }
}
/// Repeats an iterator endlessly
///
/// # Examples
///
/// ```
/// let a = [1, 2];
/// let mut it = a.iter().cycle();
/// assert_eq!(it.next().unwrap(), &1);
/// assert_eq!(it.next().unwrap(), &2);
/// assert_eq!(it.next().unwrap(), &1);
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
#[inline]
fn cycle(self) -> Cycle<Self> where Self: Sized + Clone {
Cycle{orig: self.clone(), iter: self}
}
/// Use an iterator to reverse a container in place.
#[unstable(feature = "core",
reason = "uncertain about placement or widespread use")]
fn reverse_in_place<'a, T: 'a>(&mut self) where
Self: Sized + Iterator<Item=&'a mut T> + DoubleEndedIterator
{
loop {
match (self.next(), self.next_back()) {
(Some(x), Some(y)) => mem::swap(x, y),
_ => break
}
}
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<'a, I: Iterator + ?Sized> Iterator for &'a mut I {
type Item = I::Item;
fn next(&mut self) -> Option<I::Item> { (**self).next() }
fn size_hint(&self) -> (usize, Option<usize>) { (**self).size_hint() }
}
/// Conversion from an `Iterator`
#[stable(feature = "rust1", since = "1.0.0")]
#[rustc_on_unimplemented="a collection of type `{Self}` cannot be \
built from an iterator over elements of type `{A}`"]
pub trait FromIterator<A> {
/// Build a container with elements from something iterable.
///
/// # Examples
///
/// ```
/// use std::collections::HashSet;
/// use std::iter::FromIterator;
///
/// let colors_vec = vec!["red", "red", "yellow", "blue"];
/// let colors_set = HashSet::<&str>::from_iter(colors_vec);
/// assert_eq!(colors_set.len(), 3);
/// ```
///
/// `FromIterator` is more commonly used implicitly via the
/// `Iterator::collect` method:
///
/// ```
/// use std::collections::HashSet;
///
/// let colors_vec = vec!["red", "red", "yellow", "blue"];
/// let colors_set = colors_vec.into_iter().collect::<HashSet<&str>>();
/// assert_eq!(colors_set.len(), 3);
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
fn from_iter<T: IntoIterator<Item=A>>(iterator: T) -> Self;
}
/// Conversion into an `Iterator`
///
/// Implementing this trait allows you to use your type with Rust's `for` loop. See
/// the [module level documentation](../index.html) for more details.
#[stable(feature = "rust1", since = "1.0.0")]
pub trait IntoIterator {
/// The type of the elements being iterated
#[stable(feature = "rust1", since = "1.0.0")]
type Item;
/// A container for iterating over elements of type Item
#[stable(feature = "rust1", since = "1.0.0")]
type IntoIter: Iterator<Item=Self::Item>;
/// Consumes `Self` and returns an iterator over it
#[stable(feature = "rust1", since = "1.0.0")]
fn into_iter(self) -> Self::IntoIter;
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<I: Iterator> IntoIterator for I {
type Item = I::Item;
type IntoIter = I;
fn into_iter(self) -> I {
self
}
}
/// A type growable from an `Iterator` implementation
#[stable(feature = "rust1", since = "1.0.0")]
pub trait Extend<A> {
/// Extend a container with the elements yielded by an arbitrary iterator
#[stable(feature = "rust1", since = "1.0.0")]
fn extend<T: IntoIterator<Item=A>>(&mut self, iterable: T);
}
/// A range iterator able to yield elements from both ends
///
/// A `DoubleEndedIterator` can be thought of as a deque in that `next()` and
/// `next_back()` exhaust elements from the *same* range, and do not work
/// independently of each other.
#[stable(feature = "rust1", since = "1.0.0")]
pub trait DoubleEndedIterator: Iterator {
/// Yield an element from the end of the range, returning `None` if the
/// range is empty.
#[stable(feature = "rust1", since = "1.0.0")]
fn next_back(&mut self) -> Option<Self::Item>;
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<'a, I: DoubleEndedIterator + ?Sized> DoubleEndedIterator for &'a mut I {
fn next_back(&mut self) -> Option<I::Item> { (**self).next_back() }
}
/// An object implementing random access indexing by `usize`
///
/// A `RandomAccessIterator` should be either infinite or a
/// `DoubleEndedIterator`. Calling `next()` or `next_back()` on a
/// `RandomAccessIterator` reduces the indexable range accordingly. That is,
/// `it.idx(1)` will become `it.idx(0)` after `it.next()` is called.
#[unstable(feature = "core",
reason = "not widely used, may be better decomposed into Index \
and ExactSizeIterator")]
pub trait RandomAccessIterator: Iterator {
/// Return the number of indexable elements. At most `std::usize::MAX`
/// elements are indexable, even if the iterator represents a longer range.
fn indexable(&self) -> usize;
/// Return an element at an index, or `None` if the index is out of bounds
fn idx(&mut self, index: usize) -> Option<Self::Item>;
}
/// An iterator that knows its exact length
///
/// This trait is a helper for iterators like the vector iterator, so that
/// it can support double-ended enumeration.
///
/// `Iterator::size_hint` *must* return the exact size of the iterator.
/// Note that the size must fit in `usize`.
#[stable(feature = "rust1", since = "1.0.0")]
pub trait ExactSizeIterator: Iterator {
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
/// Return the exact length of the iterator.
fn len(&self) -> usize {
let (lower, upper) = self.size_hint();
// Note: This assertion is overly defensive, but it checks the invariant
// guaranteed by the trait. If this trait were rust-internal,
// we could use debug_assert!; assert_eq! will check all Rust user
// implementations too.
assert_eq!(upper, Some(lower));
lower
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<'a, I: ExactSizeIterator + ?Sized> ExactSizeIterator for &'a mut I {}
// All adaptors that preserve the size of the wrapped iterator are fine
// Adaptors that may overflow in `size_hint` are not, i.e. `Chain`.
#[stable(feature = "rust1", since = "1.0.0")]
impl<I> ExactSizeIterator for Enumerate<I> where I: ExactSizeIterator {}
#[stable(feature = "rust1", since = "1.0.0")]
impl<I: ExactSizeIterator, F> ExactSizeIterator for Inspect<I, F> where
F: FnMut(&I::Item),
{}
#[stable(feature = "rust1", since = "1.0.0")]
impl<I> ExactSizeIterator for Rev<I>
where I: ExactSizeIterator + DoubleEndedIterator {}
#[stable(feature = "rust1", since = "1.0.0")]
impl<B, I: ExactSizeIterator, F> ExactSizeIterator for Map<I, F> where
F: FnMut(I::Item) -> B,
{}
#[stable(feature = "rust1", since = "1.0.0")]
impl<A, B> ExactSizeIterator for Zip<A, B>
where A: ExactSizeIterator, B: ExactSizeIterator {}
/// An double-ended iterator with the direction inverted
#[derive(Clone)]
#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
#[stable(feature = "rust1", since = "1.0.0")]
pub struct Rev<T> {
iter: T
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<I> Iterator for Rev<I> where I: DoubleEndedIterator {
type Item = <I as Iterator>::Item;
#[inline]
fn next(&mut self) -> Option<<I as Iterator>::Item> { self.iter.next_back() }
#[inline]
fn size_hint(&self) -> (usize, Option<usize>) { self.iter.size_hint() }
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<I> DoubleEndedIterator for Rev<I> where I: DoubleEndedIterator {
#[inline]
fn next_back(&mut self) -> Option<<I as Iterator>::Item> { self.iter.next() }
}
#[unstable(feature = "core", reason = "trait is experimental")]
impl<I> RandomAccessIterator for Rev<I>
where I: DoubleEndedIterator + RandomAccessIterator
{
#[inline]
fn indexable(&self) -> usize { self.iter.indexable() }
#[inline]
fn idx(&mut self, index: usize) -> Option<<I as Iterator>::Item> {
let amt = self.indexable();
if amt > index {
self.iter.idx(amt - index - 1)
} else {
None
}
}
}
/// A trait for iterators over elements which can be added together
#[unstable(feature = "core",
reason = "needs to be re-evaluated as part of numerics reform")]
pub trait AdditiveIterator<A> {
/// Iterates over the entire iterator, summing up all the elements
///
/// # Examples
///
/// ```
/// # #![feature(core)]
/// use std::iter::AdditiveIterator;
///
/// let a = [1, 2, 3, 4, 5];
/// let mut it = a.iter().cloned();
/// assert!(it.sum() == 15);
/// ```
fn sum(self) -> A;
}
macro_rules! impl_additive {
($A:ty, $init:expr) => {
#[unstable(feature = "core", reason = "trait is experimental")]
impl<T: Iterator<Item=$A>> AdditiveIterator<$A> for T {
#[inline]
fn sum(self) -> $A {
self.fold($init, |acc, x| acc + x)
}
}
};
}
impl_additive! { i8, 0 }
impl_additive! { i16, 0 }
impl_additive! { i32, 0 }
impl_additive! { i64, 0 }
impl_additive! { isize, 0 }
impl_additive! { u8, 0 }
impl_additive! { u16, 0 }
impl_additive! { u32, 0 }
impl_additive! { u64, 0 }
impl_additive! { usize, 0 }
impl_additive! { f32, 0.0 }
impl_additive! { f64, 0.0 }
/// A trait for iterators over elements which can be multiplied together.
#[unstable(feature = "core",
reason = "needs to be re-evaluated as part of numerics reform")]
pub trait MultiplicativeIterator<A> {
/// Iterates over the entire iterator, multiplying all the elements
///
/// # Examples
///
/// ```
/// # #![feature(core)]
/// use std::iter::MultiplicativeIterator;
///
/// fn factorial(n: usize) -> usize {
/// (1..).take_while(|&i| i <= n).product()
/// }
/// assert!(factorial(0) == 1);
/// assert!(factorial(1) == 1);
/// assert!(factorial(5) == 120);
/// ```
fn product(self) -> A;
}
macro_rules! impl_multiplicative {
($A:ty, $init:expr) => {
#[unstable(feature = "core", reason = "trait is experimental")]
impl<T: Iterator<Item=$A>> MultiplicativeIterator<$A> for T {
#[inline]
fn product(self) -> $A {
self.fold($init, |acc, x| acc * x)
}
}
};
}
impl_multiplicative! { i8, 1 }
impl_multiplicative! { i16, 1 }
impl_multiplicative! { i32, 1 }
impl_multiplicative! { i64, 1 }
impl_multiplicative! { isize, 1 }
impl_multiplicative! { u8, 1 }
impl_multiplicative! { u16, 1 }
impl_multiplicative! { u32, 1 }
impl_multiplicative! { u64, 1 }
impl_multiplicative! { usize, 1 }
impl_multiplicative! { f32, 1.0 }
impl_multiplicative! { f64, 1.0 }
/// `MinMaxResult` is an enum returned by `min_max`. See `Iterator::min_max` for
/// more detail.
#[derive(Clone, PartialEq, Debug)]
#[unstable(feature = "core",
reason = "unclear whether such a fine-grained result is widely useful")]
pub enum MinMaxResult<T> {
/// Empty iterator
NoElements,
/// Iterator with one element, so the minimum and maximum are the same
OneElement(T),
/// More than one element in the iterator, the first element is not larger
/// than the second
MinMax(T, T)
}
impl<T: Clone> MinMaxResult<T> {
/// `into_option` creates an `Option` of type `(T,T)`. The returned `Option`
/// has variant `None` if and only if the `MinMaxResult` has variant
/// `NoElements`. Otherwise variant `Some(x,y)` is returned where `x <= y`.
/// If `MinMaxResult` has variant `OneElement(x)`, performing this operation
/// will make one clone of `x`.
///
/// # Examples
///
/// ```
/// # #![feature(core)]
/// use std::iter::MinMaxResult::{self, NoElements, OneElement, MinMax};
///
/// let r: MinMaxResult<i32> = NoElements;
/// assert_eq!(r.into_option(), None);
///
/// let r = OneElement(1);
/// assert_eq!(r.into_option(), Some((1, 1)));
///
/// let r = MinMax(1, 2);
/// assert_eq!(r.into_option(), Some((1, 2)));
/// ```
#[unstable(feature = "core", reason = "type is unstable")]
pub fn into_option(self) -> Option<(T,T)> {
match self {
NoElements => None,
OneElement(x) => Some((x.clone(), x)),
MinMax(x, y) => Some((x, y))
}
}
}
/// An iterator that clones the elements of an underlying iterator
#[unstable(feature = "core", reason = "recent addition")]
#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
#[derive(Clone)]
pub struct Cloned<I> {
it: I,
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<'a, I, T: 'a> Iterator for Cloned<I>
where I: Iterator<Item=&'a T>, T: Clone
{
type Item = T;
fn next(&mut self) -> Option<T> {
self.it.next().cloned()
}
fn size_hint(&self) -> (usize, Option<usize>) {
self.it.size_hint()
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<'a, I, T: 'a> DoubleEndedIterator for Cloned<I>
where I: DoubleEndedIterator<Item=&'a T>, T: Clone
{
fn next_back(&mut self) -> Option<T> {
self.it.next_back().cloned()
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<'a, I, T: 'a> ExactSizeIterator for Cloned<I>
where I: ExactSizeIterator<Item=&'a T>, T: Clone
{}
#[unstable(feature = "core", reason = "trait is experimental")]
impl<'a, I, T: 'a> RandomAccessIterator for Cloned<I>
where I: RandomAccessIterator<Item=&'a T>, T: Clone
{
#[inline]
fn indexable(&self) -> usize {
self.it.indexable()
}
#[inline]
fn idx(&mut self, index: usize) -> Option<T> {
self.it.idx(index).cloned()
}
}
/// An iterator that repeats endlessly
#[derive(Clone)]
#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
#[stable(feature = "rust1", since = "1.0.0")]
pub struct Cycle<I> {
orig: I,
iter: I,
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<I> Iterator for Cycle<I> where I: Clone + Iterator {
type Item = <I as Iterator>::Item;
#[inline]
fn next(&mut self) -> Option<<I as Iterator>::Item> {
match self.iter.next() {
None => { self.iter = self.orig.clone(); self.iter.next() }
y => y
}
}
#[inline]
fn size_hint(&self) -> (usize, Option<usize>) {
// the cycle iterator is either empty or infinite
match self.orig.size_hint() {
sz @ (0, Some(0)) => sz,
(0, _) => (0, None),
_ => (usize::MAX, None)
}
}
}
#[unstable(feature = "core", reason = "trait is experimental")]
impl<I> RandomAccessIterator for Cycle<I> where
I: Clone + RandomAccessIterator,
{
#[inline]
fn indexable(&self) -> usize {
if self.orig.indexable() > 0 {
usize::MAX
} else {
0
}
}
#[inline]
fn idx(&mut self, index: usize) -> Option<<I as Iterator>::Item> {
let liter = self.iter.indexable();
let lorig = self.orig.indexable();
if lorig == 0 {
None
} else if index < liter {
self.iter.idx(index)
} else {
self.orig.idx((index - liter) % lorig)
}
}
}
/// An iterator that strings two iterators together
#[derive(Clone)]
#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
#[stable(feature = "rust1", since = "1.0.0")]
pub struct Chain<A, B> {
a: A,
b: B,
flag: bool,
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<A, B> Iterator for Chain<A, B> where
A: Iterator,
B: Iterator<Item = A::Item>
{
type Item = A::Item;
#[inline]
fn next(&mut self) -> Option<A::Item> {
if self.flag {
self.b.next()
} else {
match self.a.next() {
Some(x) => return Some(x),
_ => ()
}
self.flag = true;
self.b.next()
}
}
#[inline]
fn size_hint(&self) -> (usize, Option<usize>) {
let (a_lower, a_upper) = self.a.size_hint();
let (b_lower, b_upper) = self.b.size_hint();
let lower = a_lower.saturating_add(b_lower);
let upper = match (a_upper, b_upper) {
(Some(x), Some(y)) => x.checked_add(y),
_ => None
};
(lower, upper)
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<A, B> DoubleEndedIterator for Chain<A, B> where
A: DoubleEndedIterator,
B: DoubleEndedIterator<Item=A::Item>,
{
#[inline]
fn next_back(&mut self) -> Option<A::Item> {
match self.b.next_back() {
Some(x) => Some(x),
None => self.a.next_back()
}
}
}
#[unstable(feature = "core", reason = "trait is experimental")]
impl<A, B> RandomAccessIterator for Chain<A, B> where
A: RandomAccessIterator,
B: RandomAccessIterator<Item = A::Item>,
{
#[inline]
fn indexable(&self) -> usize {
let (a, b) = (self.a.indexable(), self.b.indexable());
a.saturating_add(b)
}
#[inline]
fn idx(&mut self, index: usize) -> Option<A::Item> {
let len = self.a.indexable();
if index < len {
self.a.idx(index)
} else {
self.b.idx(index - len)
}
}
}
/// An iterator that iterates two other iterators simultaneously
#[derive(Clone)]
#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
#[stable(feature = "rust1", since = "1.0.0")]
pub struct Zip<A, B> {
a: A,
b: B
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<A, B> Iterator for Zip<A, B> where A: Iterator, B: Iterator
{
type Item = (A::Item, B::Item);
#[inline]
fn next(&mut self) -> Option<(A::Item, B::Item)> {
self.a.next().and_then(|x| {
self.b.next().and_then(|y| {
Some((x, y))
})
})
}
#[inline]
fn size_hint(&self) -> (usize, Option<usize>) {
let (a_lower, a_upper) = self.a.size_hint();
let (b_lower, b_upper) = self.b.size_hint();
let lower = cmp::min(a_lower, b_lower);
let upper = match (a_upper, b_upper) {
(Some(x), Some(y)) => Some(cmp::min(x,y)),
(Some(x), None) => Some(x),
(None, Some(y)) => Some(y),
(None, None) => None
};
(lower, upper)
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<A, B> DoubleEndedIterator for Zip<A, B> where
A: DoubleEndedIterator + ExactSizeIterator,
B: DoubleEndedIterator + ExactSizeIterator,
{
#[inline]
fn next_back(&mut self) -> Option<(A::Item, B::Item)> {
let a_sz = self.a.len();
let b_sz = self.b.len();
if a_sz != b_sz {
// Adjust a, b to equal length
if a_sz > b_sz {
for _ in 0..a_sz - b_sz { self.a.next_back(); }
} else {
for _ in 0..b_sz - a_sz { self.b.next_back(); }
}
}
match (self.a.next_back(), self.b.next_back()) {
(Some(x), Some(y)) => Some((x, y)),
(None, None) => None,
_ => unreachable!(),
}
}
}
#[unstable(feature = "core", reason = "trait is experimental")]
impl<A, B> RandomAccessIterator for Zip<A, B> where
A: RandomAccessIterator,
B: RandomAccessIterator
{
#[inline]
fn indexable(&self) -> usize {
cmp::min(self.a.indexable(), self.b.indexable())
}
#[inline]
fn idx(&mut self, index: usize) -> Option<(A::Item, B::Item)> {
self.a.idx(index).and_then(|x| {
self.b.idx(index).and_then(|y| {
Some((x, y))
})
})
}
}
/// An iterator that maps the values of `iter` with `f`
#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
#[stable(feature = "rust1", since = "1.0.0")]
#[derive(Clone)]
pub struct Map<I, F> {
iter: I,
f: F,
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<B, I: Iterator, F> Iterator for Map<I, F> where F: FnMut(I::Item) -> B {
type Item = B;
#[inline]
fn next(&mut self) -> Option<B> {
self.iter.next().map(|a| (self.f)(a))
}
#[inline]
fn size_hint(&self) -> (usize, Option<usize>) {
self.iter.size_hint()
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<B, I: DoubleEndedIterator, F> DoubleEndedIterator for Map<I, F> where
F: FnMut(I::Item) -> B,
{
#[inline]
fn next_back(&mut self) -> Option<B> {
self.iter.next_back().map(|a| (self.f)(a))
}
}
#[unstable(feature = "core", reason = "trait is experimental")]
impl<B, I: RandomAccessIterator, F> RandomAccessIterator for Map<I, F> where
F: FnMut(I::Item) -> B,
{
#[inline]
fn indexable(&self) -> usize {
self.iter.indexable()
}
#[inline]
fn idx(&mut self, index: usize) -> Option<B> {
self.iter.idx(index).map(|a| (self.f)(a))
}
}
/// An iterator that filters the elements of `iter` with `predicate`
#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
#[stable(feature = "rust1", since = "1.0.0")]
#[derive(Clone)]
pub struct Filter<I, P> {
iter: I,
predicate: P,
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<I: Iterator, P> Iterator for Filter<I, P> where P: FnMut(&I::Item) -> bool {
type Item = I::Item;
#[inline]
fn next(&mut self) -> Option<I::Item> {
for x in self.iter.by_ref() {
if (self.predicate)(&x) {
return Some(x);
}
}
None
}
#[inline]
fn size_hint(&self) -> (usize, Option<usize>) {
let (_, upper) = self.iter.size_hint();
(0, upper) // can't know a lower bound, due to the predicate
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<I: DoubleEndedIterator, P> DoubleEndedIterator for Filter<I, P>
where P: FnMut(&I::Item) -> bool,
{
#[inline]
fn next_back(&mut self) -> Option<I::Item> {
for x in self.iter.by_ref().rev() {
if (self.predicate)(&x) {
return Some(x);
}
}
None
}
}
/// An iterator that uses `f` to both filter and map elements from `iter`
#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
#[stable(feature = "rust1", since = "1.0.0")]
#[derive(Clone)]
pub struct FilterMap<I, F> {
iter: I,
f: F,
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<B, I: Iterator, F> Iterator for FilterMap<I, F>
where F: FnMut(I::Item) -> Option<B>,
{
type Item = B;
#[inline]
fn next(&mut self) -> Option<B> {
for x in self.iter.by_ref() {
if let Some(y) = (self.f)(x) {
return Some(y);
}
}
None
}
#[inline]
fn size_hint(&self) -> (usize, Option<usize>) {
let (_, upper) = self.iter.size_hint();
(0, upper) // can't know a lower bound, due to the predicate
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<B, I: DoubleEndedIterator, F> DoubleEndedIterator for FilterMap<I, F>
where F: FnMut(I::Item) -> Option<B>,
{
#[inline]
fn next_back(&mut self) -> Option<B> {
for x in self.iter.by_ref().rev() {
if let Some(y) = (self.f)(x) {
return Some(y);
}
}
None
}
}
/// An iterator that yields the current count and the element during iteration
#[derive(Clone)]
#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
#[stable(feature = "rust1", since = "1.0.0")]
pub struct Enumerate<I> {
iter: I,
count: usize
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<I> Iterator for Enumerate<I> where I: Iterator {
type Item = (usize, <I as Iterator>::Item);
#[inline]
fn next(&mut self) -> Option<(usize, <I as Iterator>::Item)> {
self.iter.next().map(|a| {
let ret = (self.count, a);
self.count += 1;
ret
})
}
#[inline]
fn size_hint(&self) -> (usize, Option<usize>) {
self.iter.size_hint()
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<I> DoubleEndedIterator for Enumerate<I> where
I: ExactSizeIterator + DoubleEndedIterator
{
#[inline]
fn next_back(&mut self) -> Option<(usize, <I as Iterator>::Item)> {
self.iter.next_back().map(|a| {
let len = self.iter.len();
(self.count + len, a)
})
}
}
#[unstable(feature = "core", reason = "trait is experimental")]
impl<I> RandomAccessIterator for Enumerate<I> where I: RandomAccessIterator {
#[inline]
fn indexable(&self) -> usize {
self.iter.indexable()
}
#[inline]
fn idx(&mut self, index: usize) -> Option<(usize, <I as Iterator>::Item)> {
self.iter.idx(index).map(|a| (self.count + index, a))
}
}
/// An iterator with a `peek()` that returns an optional reference to the next element.
#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
#[stable(feature = "rust1", since = "1.0.0")]
pub struct Peekable<I: Iterator> {
iter: I,
peeked: Option<I::Item>,
}
impl<I: Iterator + Clone> Clone for Peekable<I> where I::Item: Clone {
fn clone(&self) -> Peekable<I> {
Peekable {
iter: self.iter.clone(),
peeked: self.peeked.clone(),
}
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<I: Iterator> Iterator for Peekable<I> {
type Item = I::Item;
#[inline]
fn next(&mut self) -> Option<I::Item> {
match self.peeked {
Some(_) => self.peeked.take(),
None => self.iter.next(),
}
}
#[inline]
fn size_hint(&self) -> (usize, Option<usize>) {
let (lo, hi) = self.iter.size_hint();
if self.peeked.is_some() {
let lo = lo.saturating_add(1);
let hi = hi.and_then(|x| x.checked_add(1));
(lo, hi)
} else {
(lo, hi)
}
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<I: ExactSizeIterator> ExactSizeIterator for Peekable<I> {}
#[stable(feature = "rust1", since = "1.0.0")]
impl<I: Iterator> Peekable<I> {
/// Return a reference to the next element of the iterator with out
/// advancing it, or None if the iterator is exhausted.
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
pub fn peek(&mut self) -> Option<&I::Item> {
if self.peeked.is_none() {
self.peeked = self.iter.next();
}
match self.peeked {
Some(ref value) => Some(value),
None => None,
}
}
/// Check whether peekable iterator is empty or not.
#[inline]
pub fn is_empty(&mut self) -> bool {
self.peek().is_none()
}
}
/// An iterator that rejects elements while `predicate` is true
#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
#[stable(feature = "rust1", since = "1.0.0")]
#[derive(Clone)]
pub struct SkipWhile<I, P> {
iter: I,
flag: bool,
predicate: P,
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<I: Iterator, P> Iterator for SkipWhile<I, P>
where P: FnMut(&I::Item) -> bool
{
type Item = I::Item;
#[inline]
fn next(&mut self) -> Option<I::Item> {
for x in self.iter.by_ref() {
if self.flag || !(self.predicate)(&x) {
self.flag = true;
return Some(x);
}
}
None
}
#[inline]
fn size_hint(&self) -> (usize, Option<usize>) {
let (_, upper) = self.iter.size_hint();
(0, upper) // can't know a lower bound, due to the predicate
}
}
/// An iterator that only accepts elements while `predicate` is true
#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
#[stable(feature = "rust1", since = "1.0.0")]
#[derive(Clone)]
pub struct TakeWhile<I, P> {
iter: I,
flag: bool,
predicate: P,
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<I: Iterator, P> Iterator for TakeWhile<I, P>
where P: FnMut(&I::Item) -> bool
{
type Item = I::Item;
#[inline]
fn next(&mut self) -> Option<I::Item> {
if self.flag {
None
} else {
self.iter.next().and_then(|x| {
if (self.predicate)(&x) {
Some(x)
} else {
self.flag = true;
None
}
})
}
}
#[inline]
fn size_hint(&self) -> (usize, Option<usize>) {
let (_, upper) = self.iter.size_hint();
(0, upper) // can't know a lower bound, due to the predicate
}
}
/// An iterator that skips over `n` elements of `iter`.
#[derive(Clone)]
#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
#[stable(feature = "rust1", since = "1.0.0")]
pub struct Skip<I> {
iter: I,
n: usize
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<I> Iterator for Skip<I> where I: Iterator {
type Item = <I as Iterator>::Item;
#[inline]
fn next(&mut self) -> Option<<I as Iterator>::Item> {
let mut next = self.iter.next();
if self.n == 0 {
next
} else {
let mut n = self.n;
while n > 0 {
n -= 1;
match next {
Some(_) => {
next = self.iter.next();
continue
}
None => {
self.n = 0;
return None
}
}
}
self.n = 0;
next
}
}
#[inline]
fn size_hint(&self) -> (usize, Option<usize>) {
let (lower, upper) = self.iter.size_hint();
let lower = lower.saturating_sub(self.n);
let upper = upper.map(|x| x.saturating_sub(self.n));
(lower, upper)
}
}
#[unstable(feature = "core", reason = "trait is experimental")]
impl<I> RandomAccessIterator for Skip<I> where I: RandomAccessIterator{
#[inline]
fn indexable(&self) -> usize {
self.iter.indexable().saturating_sub(self.n)
}
#[inline]
fn idx(&mut self, index: usize) -> Option<<I as Iterator>::Item> {
if index >= self.indexable() {
None
} else {
self.iter.idx(index + self.n)
}
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<I> ExactSizeIterator for Skip<I> where I: ExactSizeIterator {}
/// An iterator that only iterates over the first `n` iterations of `iter`.
#[derive(Clone)]
#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
#[stable(feature = "rust1", since = "1.0.0")]
pub struct Take<I> {
iter: I,
n: usize
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<I> Iterator for Take<I> where I: Iterator{
type Item = <I as Iterator>::Item;
#[inline]
fn next(&mut self) -> Option<<I as Iterator>::Item> {
if self.n != 0 {
self.n -= 1;
self.iter.next()
} else {
None
}
}
#[inline]
fn size_hint(&self) -> (usize, Option<usize>) {
let (lower, upper) = self.iter.size_hint();
let lower = cmp::min(lower, self.n);
let upper = match upper {
Some(x) if x < self.n => Some(x),
_ => Some(self.n)
};
(lower, upper)
}
}
#[unstable(feature = "core", reason = "trait is experimental")]
impl<I> RandomAccessIterator for Take<I> where I: RandomAccessIterator{
#[inline]
fn indexable(&self) -> usize {
cmp::min(self.iter.indexable(), self.n)
}
#[inline]
fn idx(&mut self, index: usize) -> Option<<I as Iterator>::Item> {
if index >= self.n {
None
} else {
self.iter.idx(index)
}
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<I> ExactSizeIterator for Take<I> where I: ExactSizeIterator {}
/// An iterator to maintain state while iterating another iterator
#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
#[stable(feature = "rust1", since = "1.0.0")]
#[derive(Clone)]
pub struct Scan<I, St, F> {
iter: I,
f: F,
/// The current internal state to be passed to the closure next.
#[unstable(feature = "core")]
pub state: St,
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<B, I, St, F> Iterator for Scan<I, St, F> where
I: Iterator,
F: FnMut(&mut St, I::Item) -> Option<B>,
{
type Item = B;
#[inline]
fn next(&mut self) -> Option<B> {
self.iter.next().and_then(|a| (self.f)(&mut self.state, a))
}
#[inline]
fn size_hint(&self) -> (usize, Option<usize>) {
let (_, upper) = self.iter.size_hint();
(0, upper) // can't know a lower bound, due to the scan function
}
}
/// An iterator that maps each element to an iterator,
/// and yields the elements of the produced iterators
///
#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
#[stable(feature = "rust1", since = "1.0.0")]
#[derive(Clone)]
pub struct FlatMap<I, U, F> {
iter: I,
f: F,
frontiter: Option<U>,
backiter: Option<U>,
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<I: Iterator, U: Iterator, F> Iterator for FlatMap<I, U, F>
where F: FnMut(I::Item) -> U,
{
type Item = U::Item;
#[inline]
fn next(&mut self) -> Option<U::Item> {
loop {
if let Some(ref mut inner) = self.frontiter {
for x in inner.by_ref() {
return Some(x)
}
}
match self.iter.next().map(|x| (self.f)(x)) {
None => return self.backiter.as_mut().and_then(|it| it.next()),
next => self.frontiter = next,
}
}
}
#[inline]
fn size_hint(&self) -> (usize, Option<usize>) {
let (flo, fhi) = self.frontiter.as_ref().map_or((0, Some(0)), |it| it.size_hint());
let (blo, bhi) = self.backiter.as_ref().map_or((0, Some(0)), |it| it.size_hint());
let lo = flo.saturating_add(blo);
match (self.iter.size_hint(), fhi, bhi) {
((0, Some(0)), Some(a), Some(b)) => (lo, a.checked_add(b)),
_ => (lo, None)
}
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<I: DoubleEndedIterator, U: DoubleEndedIterator, F> DoubleEndedIterator
for FlatMap<I, U, F>
where F: FnMut(I::Item) -> U
{
#[inline]
fn next_back(&mut self) -> Option<U::Item> {
loop {
if let Some(ref mut inner) = self.backiter {
match inner.next_back() {
None => (),
y => return y
}
}
match self.iter.next_back().map(|x| (self.f)(x)) {
None => return self.frontiter.as_mut().and_then(|it| it.next_back()),
next => self.backiter = next,
}
}
}
}
/// An iterator that yields `None` forever after the underlying iterator
/// yields `None` once.
#[derive(Clone)]
#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
#[stable(feature = "rust1", since = "1.0.0")]
pub struct Fuse<I> {
iter: I,
done: bool
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<I> Iterator for Fuse<I> where I: Iterator {
type Item = <I as Iterator>::Item;
#[inline]
fn next(&mut self) -> Option<<I as Iterator>::Item> {
if self.done {
None
} else {
match self.iter.next() {
None => {
self.done = true;
None
}
x => x
}
}
}
#[inline]
fn size_hint(&self) -> (usize, Option<usize>) {
if self.done {
(0, Some(0))
} else {
self.iter.size_hint()
}
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<I> DoubleEndedIterator for Fuse<I> where I: DoubleEndedIterator {
#[inline]
fn next_back(&mut self) -> Option<<I as Iterator>::Item> {
if self.done {
None
} else {
match self.iter.next_back() {
None => {
self.done = true;
None
}
x => x
}
}
}
}
// Allow RandomAccessIterators to be fused without affecting random-access behavior
#[unstable(feature = "core", reason = "trait is experimental")]
impl<I> RandomAccessIterator for Fuse<I> where I: RandomAccessIterator {
#[inline]
fn indexable(&self) -> usize {
self.iter.indexable()
}
#[inline]
fn idx(&mut self, index: usize) -> Option<<I as Iterator>::Item> {
self.iter.idx(index)
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<I> ExactSizeIterator for Fuse<I> where I: ExactSizeIterator {}
impl<I> Fuse<I> {
/// Resets the fuse such that the next call to .next() or .next_back() will
/// call the underlying iterator again even if it previously returned None.
#[inline]
#[unstable(feature = "core", reason = "seems marginal")]
pub fn reset_fuse(&mut self) {
self.done = false
}
}
/// An iterator that calls a function with a reference to each
/// element before yielding it.
#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
#[stable(feature = "rust1", since = "1.0.0")]
#[derive(Clone)]
pub struct Inspect<I, F> {
iter: I,
f: F,
}
impl<I: Iterator, F> Inspect<I, F> where F: FnMut(&I::Item) {
#[inline]
fn do_inspect(&mut self, elt: Option<I::Item>) -> Option<I::Item> {
if let Some(ref a) = elt {
(self.f)(a);
}
elt
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<I: Iterator, F> Iterator for Inspect<I, F> where F: FnMut(&I::Item) {
type Item = I::Item;
#[inline]
fn next(&mut self) -> Option<I::Item> {
let next = self.iter.next();
self.do_inspect(next)
}
#[inline]
fn size_hint(&self) -> (usize, Option<usize>) {
self.iter.size_hint()
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<I: DoubleEndedIterator, F> DoubleEndedIterator for Inspect<I, F>
where F: FnMut(&I::Item),
{
#[inline]
fn next_back(&mut self) -> Option<I::Item> {
let next = self.iter.next_back();
self.do_inspect(next)
}
}
#[unstable(feature = "core", reason = "trait is experimental")]
impl<I: RandomAccessIterator, F> RandomAccessIterator for Inspect<I, F>
where F: FnMut(&I::Item),
{
#[inline]
fn indexable(&self) -> usize {
self.iter.indexable()
}
#[inline]
fn idx(&mut self, index: usize) -> Option<I::Item> {
let element = self.iter.idx(index);
self.do_inspect(element)
}
}
/// An iterator that passes mutable state to a closure and yields the result.
///
/// # Examples
///
/// An iterator that yields sequential Fibonacci numbers, and stops on overflow.
///
/// ```
/// # #![feature(core)]
/// use std::iter::Unfold;
/// use std::num::Int; // For `.checked_add()`
///
/// // This iterator will yield up to the last Fibonacci number before the max
/// // value of `u32`. You can simply change `u32` to `u64` in this line if
/// // you want higher values than that.
/// let mut fibonacci = Unfold::new((Some(0u32), Some(1u32)),
/// |&mut (ref mut x2, ref mut x1)| {
/// // Attempt to get the next Fibonacci number
/// // `x1` will be `None` if previously overflowed.
/// let next = match (*x2, *x1) {
/// (Some(x2), Some(x1)) => x2.checked_add(x1),
/// _ => None,
/// };
///
/// // Shift left: ret <- x2 <- x1 <- next
/// let ret = *x2;
/// *x2 = *x1;
/// *x1 = next;
///
/// ret
/// });
///
/// for i in fibonacci {
/// println!("{}", i);
/// }
/// ```
#[unstable(feature = "core")]
#[derive(Clone)]
pub struct Unfold<St, F> {
f: F,
/// Internal state that will be passed to the closure on the next iteration
#[unstable(feature = "core")]
pub state: St,
}
#[unstable(feature = "core")]
impl<A, St, F> Unfold<St, F> where F: FnMut(&mut St) -> Option<A> {
/// Creates a new iterator with the specified closure as the "iterator
/// function" and an initial state to eventually pass to the closure
#[inline]
pub fn new(initial_state: St, f: F) -> Unfold<St, F> {
Unfold {
f: f,
state: initial_state
}
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<A, St, F> Iterator for Unfold<St, F> where F: FnMut(&mut St) -> Option<A> {
type Item = A;
#[inline]
fn next(&mut self) -> Option<A> {
(self.f)(&mut self.state)
}
#[inline]
fn size_hint(&self) -> (usize, Option<usize>) {
// no possible known bounds at this point
(0, None)
}
}
/// Objects that can be stepped over in both directions.
///
/// The `steps_between` function provides a way to efficiently compare
/// two `Step` objects.
#[unstable(feature = "step_trait",
reason = "likely to be replaced by finer-grained traits")]
pub trait Step: Ord {
/// Steps `self` if possible.
fn step(&self, by: &Self) -> Option<Self>;
/// The number of steps between two step objects.
///
/// `start` should always be less than `end`, so the result should never
/// be negative.
///
/// Return `None` if it is not possible to calculate steps_between
/// without overflow.
fn steps_between(start: &Self, end: &Self, by: &Self) -> Option<usize>;
}
macro_rules! step_impl {
($($t:ty)*) => ($(
impl Step for $t {
#[inline]
fn step(&self, by: &$t) -> Option<$t> {
(*self).checked_add(*by)
}
#[inline]
#[allow(trivial_numeric_casts)]
fn steps_between(start: &$t, end: &$t, by: &$t) -> Option<usize> {
if *start <= *end {
Some(((*end - *start) / *by) as usize)
} else {
Some(0)
}
}
}
)*)
}
macro_rules! step_impl_no_between {
($($t:ty)*) => ($(
impl Step for $t {
#[inline]
fn step(&self, by: &$t) -> Option<$t> {
(*self).checked_add(*by)
}
#[inline]
fn steps_between(_a: &$t, _b: &$t, _by: &$t) -> Option<usize> {
None
}
}
)*)
}
step_impl!(usize u8 u16 u32 isize i8 i16 i32);
#[cfg(target_pointer_width = "64")]
step_impl!(u64 i64);
#[cfg(target_pointer_width = "32")]
step_impl_no_between!(u64 i64);
/// An adapter for stepping range iterators by a custom amount.
///
/// The resulting iterator handles overflow by stopping. The `A`
/// parameter is the type being iterated over, while `R` is the range
/// type (usually one of `std::ops::{Range, RangeFrom}`.
#[derive(Clone)]
#[unstable(feature = "step_by", reason = "recent addition")]
pub struct StepBy<A, R> {
step_by: A,
range: R,
}
impl<A: Step> RangeFrom<A> {
/// Creates an iterator starting at the same point, but stepping by
/// the given amount at each iteration.
///
/// # Examples
///
/// ```ignore
/// for i in (0u8..).step_by(2) {
/// println!("{}", i);
/// }
/// ```
///
/// This prints all even `u8` values.
#[unstable(feature = "step_by", reason = "recent addition")]
pub fn step_by(self, by: A) -> StepBy<A, Self> {
StepBy {
step_by: by,
range: self
}
}
}
#[allow(deprecated)]
impl<A: Step> ops::Range<A> {
/// Creates an iterator with the same range, but stepping by the
/// given amount at each iteration.
///
/// The resulting iterator handles overflow by stopping.
///
/// # Examples
///
/// ```
/// # #![feature(step_by, core)]
/// for i in (0..10).step_by(2) {
/// println!("{}", i);
/// }
/// ```
///
/// This prints:
///
/// ```text
/// 0
/// 2
/// 4
/// 6
/// 8
/// ```
#[unstable(feature = "step_by", reason = "recent addition")]
pub fn step_by(self, by: A) -> StepBy<A, Self> {
StepBy {
step_by: by,
range: self
}
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<A> Iterator for StepBy<A, RangeFrom<A>> where
A: Clone,
for<'a> &'a A: Add<&'a A, Output = A>
{
type Item = A;
#[inline]
fn next(&mut self) -> Option<A> {
let mut n = &self.range.start + &self.step_by;
mem::swap(&mut n, &mut self.range.start);
Some(n)
}
#[inline]
fn size_hint(&self) -> (usize, Option<usize>) {
(usize::MAX, None) // Too bad we can't specify an infinite lower bound
}
}
/// An iterator over the range [start, stop]
#[derive(Clone)]
#[unstable(feature = "core",
reason = "likely to be replaced by range notation and adapters")]
pub struct RangeInclusive<A> {
range: ops::Range<A>,
done: bool,
}
/// Return an iterator over the range [start, stop]
#[inline]
#[unstable(feature = "core",
reason = "likely to be replaced by range notation and adapters")]
pub fn range_inclusive<A>(start: A, stop: A) -> RangeInclusive<A>
where A: Step + One + Clone
{
RangeInclusive {
range: start..stop,
done: false,
}
}
#[unstable(feature = "core",
reason = "likely to be replaced by range notation and adapters")]
impl<A: Step + One + Clone> Iterator for RangeInclusive<A> {
type Item = A;
#[inline]
fn next(&mut self) -> Option<A> {
self.range.next().or_else(|| {
if !self.done && self.range.start == self.range.end {
self.done = true;
Some(self.range.end.clone())
} else {
None
}
})
}
#[inline]
fn size_hint(&self) -> (usize, Option<usize>) {
let (lo, hi) = self.range.size_hint();
if self.done {
(lo, hi)
} else {
let lo = lo.saturating_add(1);
let hi = hi.and_then(|x| x.checked_add(1));
(lo, hi)
}
}
}
#[unstable(feature = "core",
reason = "likely to be replaced by range notation and adapters")]
impl<A> DoubleEndedIterator for RangeInclusive<A>
where A: Step + One + Clone,
for<'a> &'a A: Sub<Output=A>
{
#[inline]
fn next_back(&mut self) -> Option<A> {
if self.range.end > self.range.start {
let result = self.range.end.clone();
self.range.end = &self.range.end - &A::one();
Some(result)
} else if !self.done && self.range.start == self.range.end {
self.done = true;
Some(self.range.end.clone())
} else {
None
}
}
}
#[stable(feature = "rust1", since = "1.0.0")]
#[allow(deprecated)]
impl<A: Step + Zero + Clone> Iterator for StepBy<A, ops::Range<A>> {
type Item = A;
#[inline]
fn next(&mut self) -> Option<A> {
let rev = self.step_by < A::zero();
if (rev && self.range.start > self.range.end) ||
(!rev && self.range.start < self.range.end)
{
match self.range.start.step(&self.step_by) {
Some(mut n) => {
mem::swap(&mut self.range.start, &mut n);
Some(n)
},
None => {
let mut n = self.range.end.clone();
mem::swap(&mut self.range.start, &mut n);
Some(n)
}
}
} else {
None
}
}
}
/// An iterator over the range [start, stop] by `step`. It handles overflow by stopping.
#[derive(Clone)]
#[unstable(feature = "core",
reason = "likely to be replaced by range notation and adapters")]
pub struct RangeStepInclusive<A> {
state: A,
stop: A,
step: A,
rev: bool,
done: bool,
}
/// Return an iterator over the range [start, stop] by `step`.
///
/// It handles overflow by stopping.
///
/// # Examples
///
/// ```
/// # #![feature(core)]
/// use std::iter::range_step_inclusive;
///
/// for i in range_step_inclusive(0, 10, 2) {
/// println!("{}", i);
/// }
/// ```
///
/// This prints:
///
/// ```text
/// 0
/// 2
/// 4
/// 6
/// 8
/// 10
/// ```
#[inline]
#[unstable(feature = "core",
reason = "likely to be replaced by range notation and adapters")]
#[allow(deprecated)]
pub fn range_step_inclusive<A: Int>(start: A, stop: A, step: A) -> RangeStepInclusive<A> {
let rev = step < Int::zero();
RangeStepInclusive {
state: start,
stop: stop,
step: step,
rev: rev,
done: false,
}
}
#[unstable(feature = "core",
reason = "likely to be replaced by range notation and adapters")]
#[allow(deprecated)]
impl<A: Int> Iterator for RangeStepInclusive<A> {
type Item = A;
#[inline]
fn next(&mut self) -> Option<A> {
if !self.done && ((self.rev && self.state >= self.stop) ||
(!self.rev && self.state <= self.stop)) {
let result = self.state;
match self.state.checked_add(self.step) {
Some(x) => self.state = x,
None => self.done = true
}
Some(result)
} else {
None
}
}
}
macro_rules! range_exact_iter_impl {
($($t:ty)*) => ($(
#[stable(feature = "rust1", since = "1.0.0")]
impl ExactSizeIterator for ops::Range<$t> { }
)*)
}
#[stable(feature = "rust1", since = "1.0.0")]
#[allow(deprecated)]
impl<A: Step + One + Clone> Iterator for ops::Range<A> {
type Item = A;
#[inline]
fn next(&mut self) -> Option<A> {
if self.start < self.end {
match self.start.step(&A::one()) {
Some(mut n) => {
mem::swap(&mut n, &mut self.start);
Some(n)
},
None => {
let mut n = self.end.clone();
mem::swap(&mut n, &mut self.start);
Some(n)
}
}
} else {
None
}
}
#[inline]
fn size_hint(&self) -> (usize, Option<usize>) {
match Step::steps_between(&self.start, &self.end, &A::one()) {
Some(hint) => (hint, Some(hint)),
None => (0, None)
}
}
}
// Ranges of u64 and i64 are excluded because they cannot guarantee having
// a length <= usize::MAX, which is required by ExactSizeIterator.
range_exact_iter_impl!(usize u8 u16 u32 isize i8 i16 i32);
#[stable(feature = "rust1", since = "1.0.0")]
#[allow(deprecated)]
impl<A: Step + One + Clone> DoubleEndedIterator for ops::Range<A> where
for<'a> &'a A: Sub<&'a A, Output = A>
{
#[inline]
fn next_back(&mut self) -> Option<A> {
if self.start < self.end {
self.end = &self.end - &A::one();
Some(self.end.clone())
} else {
None
}
}
}
#[stable(feature = "rust1", since = "1.0.0")]
#[allow(deprecated)]
impl<A: Step + One> Iterator for ops::RangeFrom<A> {
type Item = A;
#[inline]
fn next(&mut self) -> Option<A> {
self.start.step(&A::one()).map(|mut n| {
mem::swap(&mut n, &mut self.start);
n
})
}
}
/// An iterator that repeats an element endlessly
#[derive(Clone)]
#[stable(feature = "rust1", since = "1.0.0")]
pub struct Repeat<A> {
element: A
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<A: Clone> Iterator for Repeat<A> {
type Item = A;
#[inline]
fn next(&mut self) -> Option<A> { self.idx(0) }
#[inline]
fn size_hint(&self) -> (usize, Option<usize>) { (usize::MAX, None) }
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<A: Clone> DoubleEndedIterator for Repeat<A> {
#[inline]
fn next_back(&mut self) -> Option<A> { self.idx(0) }
}
#[unstable(feature = "core", reason = "trait is experimental")]
impl<A: Clone> RandomAccessIterator for Repeat<A> {
#[inline]
fn indexable(&self) -> usize { usize::MAX }
#[inline]
fn idx(&mut self, _: usize) -> Option<A> { Some(self.element.clone()) }
}
type IterateState<T, F> = (F, Option<T>, bool);
/// An iterator that repeatedly applies a given function, starting
/// from a given seed value.
#[unstable(feature = "core")]
pub type Iterate<T, F> = Unfold<IterateState<T, F>, fn(&mut IterateState<T, F>) -> Option<T>>;
/// Create a new iterator that produces an infinite sequence of
/// repeated applications of the given function `f`.
#[unstable(feature = "core")]
pub fn iterate<T, F>(seed: T, f: F) -> Iterate<T, F> where
T: Clone,
F: FnMut(T) -> T,
{
fn next<T, F>(st: &mut IterateState<T, F>) -> Option<T> where
T: Clone,
F: FnMut(T) -> T,
{
let &mut (ref mut f, ref mut val, ref mut first) = st;
if *first {
*first = false;
} else if let Some(x) = val.take() {
*val = Some((*f)(x))
}
val.clone()
}
// coerce to a fn pointer
let next: fn(&mut IterateState<T,F>) -> Option<T> = next;
Unfold::new((f, Some(seed), true), next)
}
/// Create a new iterator that endlessly repeats the element `elt`.
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
pub fn repeat<T: Clone>(elt: T) -> Repeat<T> {
Repeat{element: elt}
}
/// Functions for lexicographical ordering of sequences.
///
/// Lexicographical ordering through `<`, `<=`, `>=`, `>` requires
/// that the elements implement both `PartialEq` and `PartialOrd`.
///
/// If two sequences are equal up until the point where one ends,
/// the shorter sequence compares less.
#[unstable(feature = "core", reason = "needs review and revision")]
pub mod order {
use cmp;
use cmp::{Eq, Ord, PartialOrd, PartialEq};
use cmp::Ordering::{Equal, Less, Greater};
use option::Option;
use option::Option::{Some, None};
use super::Iterator;
/// Compare `a` and `b` for equality using `Eq`
pub fn equals<A, L, R>(mut a: L, mut b: R) -> bool where
A: Eq,
L: Iterator<Item=A>,
R: Iterator<Item=A>,
{
loop {
match (a.next(), b.next()) {
(None, None) => return true,
(None, _) | (_, None) => return false,
(Some(x), Some(y)) => if x != y { return false },
}
}
}
/// Order `a` and `b` lexicographically using `Ord`
pub fn cmp<A, L, R>(mut a: L, mut b: R) -> cmp::Ordering where
A: Ord,
L: Iterator<Item=A>,
R: Iterator<Item=A>,
{
loop {
match (a.next(), b.next()) {
(None, None) => return Equal,
(None, _ ) => return Less,
(_ , None) => return Greater,
(Some(x), Some(y)) => match x.cmp(&y) {
Equal => (),
non_eq => return non_eq,
},
}
}
}
/// Order `a` and `b` lexicographically using `PartialOrd`
pub fn partial_cmp<L: Iterator, R: Iterator>(mut a: L, mut b: R) -> Option<cmp::Ordering> where
L::Item: PartialOrd<R::Item>
{
loop {
match (a.next(), b.next()) {
(None, None) => return Some(Equal),
(None, _ ) => return Some(Less),
(_ , None) => return Some(Greater),
(Some(x), Some(y)) => match x.partial_cmp(&y) {
Some(Equal) => (),
non_eq => return non_eq,
},
}
}
}
/// Compare `a` and `b` for equality (Using partial equality, `PartialEq`)
pub fn eq<L: Iterator, R: Iterator>(mut a: L, mut b: R) -> bool where
L::Item: PartialEq<R::Item>,
{
loop {
match (a.next(), b.next()) {
(None, None) => return true,
(None, _) | (_, None) => return false,
(Some(x), Some(y)) => if !x.eq(&y) { return false },
}
}
}
/// Compare `a` and `b` for nonequality (Using partial equality, `PartialEq`)
pub fn ne<L: Iterator, R: Iterator>(mut a: L, mut b: R) -> bool where
L::Item: PartialEq<R::Item>,
{
loop {
match (a.next(), b.next()) {
(None, None) => return false,
(None, _) | (_, None) => return true,
(Some(x), Some(y)) => if x.ne(&y) { return true },
}
}
}
/// Return `a` < `b` lexicographically (Using partial order, `PartialOrd`)
pub fn lt<R: Iterator, L: Iterator>(mut a: L, mut b: R) -> bool where
L::Item: PartialOrd<R::Item>,
{
loop {
match (a.next(), b.next()) {
(None, None) => return false,
(None, _ ) => return true,
(_ , None) => return false,
(Some(x), Some(y)) => if x.ne(&y) { return x.lt(&y) },
}
}
}
/// Return `a` <= `b` lexicographically (Using partial order, `PartialOrd`)
pub fn le<L: Iterator, R: Iterator>(mut a: L, mut b: R) -> bool where
L::Item: PartialOrd<R::Item>,
{
loop {
match (a.next(), b.next()) {
(None, None) => return true,
(None, _ ) => return true,
(_ , None) => return false,
(Some(x), Some(y)) => if x.ne(&y) { return x.le(&y) },
}
}
}
/// Return `a` > `b` lexicographically (Using partial order, `PartialOrd`)
pub fn gt<L: Iterator, R: Iterator>(mut a: L, mut b: R) -> bool where
L::Item: PartialOrd<R::Item>,
{
loop {
match (a.next(), b.next()) {
(None, None) => return false,
(None, _ ) => return false,
(_ , None) => return true,
(Some(x), Some(y)) => if x.ne(&y) { return x.gt(&y) },
}
}
}
/// Return `a` >= `b` lexicographically (Using partial order, `PartialOrd`)
pub fn ge<L: Iterator, R: Iterator>(mut a: L, mut b: R) -> bool where
L::Item: PartialOrd<R::Item>,
{
loop {
match (a.next(), b.next()) {
(None, None) => return true,
(None, _ ) => return false,
(_ , None) => return true,
(Some(x), Some(y)) => if x.ne(&y) { return x.ge(&y) },
}
}
}
}
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