2203 lines
70 KiB
Rust
2203 lines
70 KiB
Rust
// Copyright 2013-2016 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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use cmp::Ordering;
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use super::{Chain, Cycle, Cloned, Enumerate, Filter, FilterMap, FlatMap, Fuse};
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use super::{Inspect, Map, Peekable, Scan, Skip, SkipWhile, Take, TakeWhile, Rev};
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use super::{Zip, Sum, Product};
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use super::{ChainState, FromIterator, ZipImpl};
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fn _assert_is_object_safe(_: &Iterator<Item=()>) {}
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/// An interface for dealing with iterators.
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///
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/// This is the main iterator trait. For more about the concept of iterators
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/// generally, please see the [module-level documentation]. In particular, you
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/// may want to know how to [implement `Iterator`][impl].
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///
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/// [module-level documentation]: index.html
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/// [impl]: index.html#implementing-iterator
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#[stable(feature = "rust1", since = "1.0.0")]
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#[rustc_on_unimplemented = "`{Self}` is not an iterator; maybe try calling \
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`.iter()` or a similar method"]
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pub trait Iterator {
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/// The type of the elements being iterated over.
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#[stable(feature = "rust1", since = "1.0.0")]
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type Item;
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/// Advances the iterator and returns the next value.
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///
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/// Returns [`None`] when iteration is finished. Individual iterator
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/// implementations may choose to resume iteration, and so calling `next()`
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/// again may or may not eventually start returning [`Some(Item)`] again at some
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/// point.
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///
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/// [`None`]: ../../std/option/enum.Option.html#variant.None
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/// [`Some(Item)`]: ../../std/option/enum.Option.html#variant.Some
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///
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/// # Examples
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///
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/// Basic usage:
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///
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/// ```
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/// let a = [1, 2, 3];
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///
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/// let mut iter = a.iter();
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///
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/// // A call to next() returns the next value...
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/// assert_eq!(Some(&1), iter.next());
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/// assert_eq!(Some(&2), iter.next());
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/// assert_eq!(Some(&3), iter.next());
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///
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/// // ... and then None once it's over.
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/// assert_eq!(None, iter.next());
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///
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/// // More calls may or may not return None. Here, they always will.
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/// assert_eq!(None, iter.next());
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/// assert_eq!(None, iter.next());
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/// ```
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#[stable(feature = "rust1", since = "1.0.0")]
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fn next(&mut self) -> Option<Self::Item>;
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/// Returns the bounds on the remaining length of the iterator.
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///
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/// Specifically, `size_hint()` returns a tuple where the first element
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/// is the lower bound, and the second element is the upper bound.
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///
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/// The second half of the tuple that is returned is an [`Option`]`<`[`usize`]`>`.
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/// A [`None`] here means that either there is no known upper bound, or the
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/// upper bound is larger than [`usize`].
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///
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/// # Implementation notes
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///
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/// It is not enforced that an iterator implementation yields the declared
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/// number of elements. A buggy iterator may yield less than the lower bound
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/// or more than the upper bound of elements.
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///
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/// `size_hint()` is primarily intended to be used for optimizations such as
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/// reserving space for the elements of the iterator, but must not be
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/// trusted to e.g. omit bounds checks in unsafe code. An incorrect
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/// implementation of `size_hint()` should not lead to memory safety
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/// violations.
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///
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/// That said, the implementation should provide a correct estimation,
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/// because otherwise it would be a violation of the trait's protocol.
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///
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/// The default implementation returns `(0, None)` which is correct for any
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/// iterator.
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///
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/// [`usize`]: ../../std/primitive.usize.html
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/// [`Option`]: ../../std/option/enum.Option.html
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/// [`None`]: ../../std/option/enum.Option.html#variant.None
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///
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/// # Examples
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///
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/// Basic usage:
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///
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/// ```
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/// let a = [1, 2, 3];
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/// let iter = a.iter();
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///
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/// assert_eq!((3, Some(3)), iter.size_hint());
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/// ```
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///
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/// A more complex example:
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///
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/// ```
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/// // The even numbers from zero to ten.
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/// let iter = (0..10).filter(|x| x % 2 == 0);
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///
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/// // We might iterate from zero to ten times. Knowing that it's five
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/// // exactly wouldn't be possible without executing filter().
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/// assert_eq!((0, Some(10)), iter.size_hint());
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///
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/// // Let's add one five more numbers with chain()
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/// let iter = (0..10).filter(|x| x % 2 == 0).chain(15..20);
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///
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/// // now both bounds are increased by five
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/// assert_eq!((5, Some(15)), iter.size_hint());
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/// ```
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///
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/// Returning `None` for an upper bound:
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///
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/// ```
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/// // an infinite iterator has no upper bound
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/// let iter = 0..;
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///
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/// assert_eq!((0, None), iter.size_hint());
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/// ```
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#[inline]
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#[stable(feature = "rust1", since = "1.0.0")]
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fn size_hint(&self) -> (usize, Option<usize>) { (0, None) }
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/// Consumes the iterator, counting the number of iterations and returning it.
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///
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/// This method will evaluate the iterator until its [`next()`] returns
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/// [`None`]. Once [`None`] is encountered, `count()` returns the number of
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/// times it called [`next()`].
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///
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/// [`next()`]: #tymethod.next
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/// [`None`]: ../../std/option/enum.Option.html#variant.None
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///
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/// # Overflow Behavior
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///
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/// The method does no guarding against overflows, so counting elements of
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/// an iterator with more than [`usize::MAX`] elements either produces the
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/// wrong result or panics. If debug assertions are enabled, a panic is
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/// guaranteed.
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///
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/// # Panics
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///
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/// This function might panic if the iterator has more than [`usize::MAX`]
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/// elements.
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///
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/// [`usize::MAX`]: ../../std/isize/constant.MAX.html
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///
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/// # Examples
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///
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/// Basic usage:
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///
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/// ```
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/// let a = [1, 2, 3];
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/// assert_eq!(a.iter().count(), 3);
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///
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/// let a = [1, 2, 3, 4, 5];
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/// assert_eq!(a.iter().count(), 5);
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/// ```
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#[inline]
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#[rustc_inherit_overflow_checks]
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#[stable(feature = "rust1", since = "1.0.0")]
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fn count(self) -> usize where Self: Sized {
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// Might overflow.
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self.fold(0, |cnt, _| cnt + 1)
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}
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/// Consumes the iterator, returning the last element.
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///
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/// This method will evaluate the iterator until it returns [`None`]. While
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/// doing so, it keeps track of the current element. After [`None`] is
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/// returned, `last()` will then return the last element it saw.
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///
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/// [`None`]: ../../std/option/enum.Option.html#variant.None
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///
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/// # Examples
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///
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/// Basic usage:
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///
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/// ```
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/// let a = [1, 2, 3];
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/// assert_eq!(a.iter().last(), Some(&3));
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///
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/// let a = [1, 2, 3, 4, 5];
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/// assert_eq!(a.iter().last(), Some(&5));
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/// ```
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#[inline]
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#[stable(feature = "rust1", since = "1.0.0")]
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fn last(self) -> Option<Self::Item> where Self: Sized {
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let mut last = None;
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for x in self { last = Some(x); }
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last
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}
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/// Returns the `n`th element of the iterator.
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///
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/// Like most indexing operations, the count starts from zero, so `nth(0)`
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/// returns the first value, `nth(1)` the second, and so on.
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///
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/// Note that all preceding elements, as well as the returned element, will be
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/// consumed from the iterator. That means that the preceding elements will be
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/// discarded, and also that calling `nth(0)` multiple times on the same iterator
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/// will return different elements.
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///
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/// `nth()` will return [`None`] if `n` is greater than or equal to the length of the
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/// iterator.
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///
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/// [`None`]: ../../std/option/enum.Option.html#variant.None
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///
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/// # Examples
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///
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/// Basic usage:
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///
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/// ```
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/// let a = [1, 2, 3];
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/// assert_eq!(a.iter().nth(1), Some(&2));
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/// ```
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///
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/// Calling `nth()` multiple times doesn't rewind the iterator:
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///
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/// ```
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/// let a = [1, 2, 3];
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///
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/// let mut iter = a.iter();
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///
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/// assert_eq!(iter.nth(1), Some(&2));
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/// assert_eq!(iter.nth(1), None);
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/// ```
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///
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/// Returning `None` if there are less than `n + 1` elements:
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///
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/// ```
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/// let a = [1, 2, 3];
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/// assert_eq!(a.iter().nth(10), None);
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/// ```
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#[inline]
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#[stable(feature = "rust1", since = "1.0.0")]
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fn nth(&mut self, mut n: usize) -> Option<Self::Item> {
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for x in self {
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if n == 0 { return Some(x) }
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n -= 1;
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}
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None
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}
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/// Takes two iterators and creates a new iterator over both in sequence.
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///
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/// `chain()` will return a new iterator which will first iterate over
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/// values from the first iterator and then over values from the second
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/// iterator.
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///
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/// In other words, it links two iterators together, in a chain. 🔗
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///
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/// # Examples
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///
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/// Basic usage:
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///
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/// ```
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/// let a1 = [1, 2, 3];
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/// let a2 = [4, 5, 6];
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///
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/// let mut iter = a1.iter().chain(a2.iter());
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///
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/// assert_eq!(iter.next(), Some(&1));
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/// assert_eq!(iter.next(), Some(&2));
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/// assert_eq!(iter.next(), Some(&3));
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/// assert_eq!(iter.next(), Some(&4));
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/// assert_eq!(iter.next(), Some(&5));
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/// assert_eq!(iter.next(), Some(&6));
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/// assert_eq!(iter.next(), None);
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/// ```
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///
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/// Since the argument to `chain()` uses [`IntoIterator`], we can pass
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/// anything that can be converted into an [`Iterator`], not just an
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/// [`Iterator`] itself. For example, slices (`&[T]`) implement
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/// [`IntoIterator`], and so can be passed to `chain()` directly:
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///
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/// [`IntoIterator`]: trait.IntoIterator.html
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/// [`Iterator`]: trait.Iterator.html
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///
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/// ```
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/// let s1 = &[1, 2, 3];
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/// let s2 = &[4, 5, 6];
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///
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/// let mut iter = s1.iter().chain(s2);
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///
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/// assert_eq!(iter.next(), Some(&1));
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/// assert_eq!(iter.next(), Some(&2));
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/// assert_eq!(iter.next(), Some(&3));
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/// assert_eq!(iter.next(), Some(&4));
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/// assert_eq!(iter.next(), Some(&5));
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/// assert_eq!(iter.next(), Some(&6));
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/// assert_eq!(iter.next(), None);
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/// ```
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#[inline]
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#[stable(feature = "rust1", since = "1.0.0")]
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fn chain<U>(self, other: U) -> Chain<Self, U::IntoIter> where
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Self: Sized, U: IntoIterator<Item=Self::Item>,
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{
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Chain{a: self, b: other.into_iter(), state: ChainState::Both}
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}
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/// 'Zips up' two iterators into a single iterator of pairs.
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///
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/// `zip()` returns a new iterator that will iterate over two other
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/// iterators, returning a tuple where the first element comes from the
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/// first iterator, and the second element comes from the second iterator.
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///
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/// In other words, it zips two iterators together, into a single one.
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///
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/// When either iterator returns [`None`], all further calls to [`next()`]
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/// will return [`None`].
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///
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/// # Examples
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///
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/// Basic usage:
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///
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/// ```
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/// let a1 = [1, 2, 3];
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/// let a2 = [4, 5, 6];
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///
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/// let mut iter = a1.iter().zip(a2.iter());
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///
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/// assert_eq!(iter.next(), Some((&1, &4)));
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/// assert_eq!(iter.next(), Some((&2, &5)));
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/// assert_eq!(iter.next(), Some((&3, &6)));
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/// assert_eq!(iter.next(), None);
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/// ```
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///
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/// Since the argument to `zip()` uses [`IntoIterator`], we can pass
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/// anything that can be converted into an [`Iterator`], not just an
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/// [`Iterator`] itself. For example, slices (`&[T]`) implement
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/// [`IntoIterator`], and so can be passed to `zip()` directly:
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///
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/// [`IntoIterator`]: trait.IntoIterator.html
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/// [`Iterator`]: trait.Iterator.html
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///
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/// ```
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/// let s1 = &[1, 2, 3];
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/// let s2 = &[4, 5, 6];
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///
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/// let mut iter = s1.iter().zip(s2);
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///
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/// assert_eq!(iter.next(), Some((&1, &4)));
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/// assert_eq!(iter.next(), Some((&2, &5)));
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/// assert_eq!(iter.next(), Some((&3, &6)));
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/// assert_eq!(iter.next(), None);
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/// ```
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///
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/// `zip()` is often used to zip an infinite iterator to a finite one.
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/// This works because the finite iterator will eventually return [`None`],
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/// ending the zipper. Zipping with `(0..)` can look a lot like [`enumerate()`]:
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///
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/// ```
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/// let enumerate: Vec<_> = "foo".chars().enumerate().collect();
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///
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/// let zipper: Vec<_> = (0..).zip("foo".chars()).collect();
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///
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/// assert_eq!((0, 'f'), enumerate[0]);
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/// assert_eq!((0, 'f'), zipper[0]);
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///
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/// assert_eq!((1, 'o'), enumerate[1]);
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/// assert_eq!((1, 'o'), zipper[1]);
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///
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/// assert_eq!((2, 'o'), enumerate[2]);
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/// assert_eq!((2, 'o'), zipper[2]);
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/// ```
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///
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/// [`enumerate()`]: trait.Iterator.html#method.enumerate
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/// [`next()`]: ../../std/iter/trait.Iterator.html#tymethod.next
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/// [`None`]: ../../std/option/enum.Option.html#variant.None
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#[inline]
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#[stable(feature = "rust1", since = "1.0.0")]
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fn zip<U>(self, other: U) -> Zip<Self, U::IntoIter> where
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Self: Sized, U: IntoIterator
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{
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Zip::new(self, other.into_iter())
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}
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/// Takes a closure and creates an iterator which calls that closure on each
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/// element.
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///
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/// `map()` transforms one iterator into another, by means of its argument:
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/// something that implements `FnMut`. It produces a new iterator which
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/// calls this closure on each element of the original iterator.
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///
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/// If you are good at thinking in types, you can think of `map()` like this:
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/// If you have an iterator that gives you elements of some type `A`, and
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/// you want an iterator of some other type `B`, you can use `map()`,
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/// passing a closure that takes an `A` and returns a `B`.
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///
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/// `map()` is conceptually similar to a [`for`] loop. However, as `map()` is
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/// lazy, it is best used when you're already working with other iterators.
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/// If you're doing some sort of looping for a side effect, it's considered
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/// more idiomatic to use [`for`] than `map()`.
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///
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/// [`for`]: ../../book/loops.html#for
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///
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/// # Examples
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///
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/// Basic usage:
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///
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/// ```
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/// let a = [1, 2, 3];
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///
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/// let mut iter = a.into_iter().map(|x| 2 * x);
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///
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/// assert_eq!(iter.next(), Some(2));
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/// assert_eq!(iter.next(), Some(4));
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/// assert_eq!(iter.next(), Some(6));
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/// assert_eq!(iter.next(), None);
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/// ```
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///
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/// If you're doing some sort of side effect, prefer [`for`] to `map()`:
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///
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/// ```
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/// # #![allow(unused_must_use)]
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/// // don't do this:
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/// (0..5).map(|x| println!("{}", x));
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///
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/// // it won't even execute, as it is lazy. Rust will warn you about this.
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///
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/// // Instead, use for:
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/// for x in 0..5 {
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/// println!("{}", x);
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/// }
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/// ```
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#[inline]
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#[stable(feature = "rust1", since = "1.0.0")]
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fn map<B, F>(self, f: F) -> Map<Self, F> where
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Self: Sized, F: FnMut(Self::Item) -> B,
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{
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Map{iter: self, f: f}
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}
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/// Creates an iterator which uses a closure to determine if an element
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/// should be yielded.
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///
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/// The closure must return `true` or `false`. `filter()` creates an
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/// iterator which calls this closure on each element. If the closure
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/// returns `true`, then the element is returned. If the closure returns
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/// `false`, it will try again, and call the closure on the next element,
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/// seeing if it passes the test.
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///
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/// # Examples
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///
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/// Basic usage:
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///
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/// ```
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/// let a = [0i32, 1, 2];
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///
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/// let mut iter = a.into_iter().filter(|x| x.is_positive());
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///
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/// assert_eq!(iter.next(), Some(&1));
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/// assert_eq!(iter.next(), Some(&2));
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/// assert_eq!(iter.next(), None);
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/// ```
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///
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/// Because the closure passed to `filter()` takes a reference, and many
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/// iterators iterate over references, this leads to a possibly confusing
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/// situation, where the type of the closure is a double reference:
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///
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/// ```
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/// let a = [0, 1, 2];
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///
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/// let mut iter = a.into_iter().filter(|x| **x > 1); // need two *s!
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///
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/// assert_eq!(iter.next(), Some(&2));
|
|
/// assert_eq!(iter.next(), None);
|
|
/// ```
|
|
///
|
|
/// It's common to instead use destructuring on the argument to strip away
|
|
/// one:
|
|
///
|
|
/// ```
|
|
/// let a = [0, 1, 2];
|
|
///
|
|
/// let mut iter = a.into_iter().filter(|&x| *x > 1); // both & and *
|
|
///
|
|
/// assert_eq!(iter.next(), Some(&2));
|
|
/// assert_eq!(iter.next(), None);
|
|
/// ```
|
|
///
|
|
/// or both:
|
|
///
|
|
/// ```
|
|
/// let a = [0, 1, 2];
|
|
///
|
|
/// let mut iter = a.into_iter().filter(|&&x| x > 1); // two &s
|
|
///
|
|
/// assert_eq!(iter.next(), Some(&2));
|
|
/// assert_eq!(iter.next(), None);
|
|
/// ```
|
|
///
|
|
/// of these layers.
|
|
#[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.
|
|
///
|
|
/// The closure must return an [`Option<T>`]. `filter_map()` creates an
|
|
/// iterator which calls this closure on each element. If the closure
|
|
/// returns [`Some(element)`][`Some`], then that element is returned. If the
|
|
/// closure returns [`None`], it will try again, and call the closure on the
|
|
/// next element, seeing if it will return [`Some`].
|
|
///
|
|
/// Why `filter_map()` and not just [`filter()`].[`map()`]? The key is in this
|
|
/// part:
|
|
///
|
|
/// [`filter()`]: #method.filter
|
|
/// [`map()`]: #method.map
|
|
///
|
|
/// > If the closure returns [`Some(element)`][`Some`], then that element is returned.
|
|
///
|
|
/// In other words, it removes the [`Option<T>`] layer automatically. If your
|
|
/// mapping is already returning an [`Option<T>`] and you want to skip over
|
|
/// [`None`]s, then `filter_map()` is much, much nicer to use.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// Basic usage:
|
|
///
|
|
/// ```
|
|
/// let a = ["1", "2", "lol"];
|
|
///
|
|
/// let mut iter = a.iter().filter_map(|s| s.parse().ok());
|
|
///
|
|
/// assert_eq!(iter.next(), Some(1));
|
|
/// assert_eq!(iter.next(), Some(2));
|
|
/// assert_eq!(iter.next(), None);
|
|
/// ```
|
|
///
|
|
/// Here's the same example, but with [`filter()`] and [`map()`]:
|
|
///
|
|
/// ```
|
|
/// let a = ["1", "2", "lol"];
|
|
///
|
|
/// let mut iter = a.iter()
|
|
/// .map(|s| s.parse().ok())
|
|
/// .filter(|s| s.is_some());
|
|
///
|
|
/// assert_eq!(iter.next(), Some(Some(1)));
|
|
/// assert_eq!(iter.next(), Some(Some(2)));
|
|
/// assert_eq!(iter.next(), None);
|
|
/// ```
|
|
///
|
|
/// There's an extra layer of [`Some`] in there.
|
|
///
|
|
/// [`Option<T>`]: ../../std/option/enum.Option.html
|
|
/// [`Some`]: ../../std/option/enum.Option.html#variant.Some
|
|
/// [`None`]: ../../std/option/enum.Option.html#variant.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 which gives the current iteration count as well as
|
|
/// the next value.
|
|
///
|
|
/// The iterator returned yields pairs `(i, val)`, where `i` is the
|
|
/// current index of iteration and `val` is the value returned by the
|
|
/// iterator.
|
|
///
|
|
/// `enumerate()` keeps its count as a [`usize`]. If you want to count by a
|
|
/// different sized integer, the [`zip()`] function provides similar
|
|
/// functionality.
|
|
///
|
|
/// # Overflow Behavior
|
|
///
|
|
/// The method does no guarding against overflows, so enumerating more than
|
|
/// [`usize::MAX`] elements either produces the wrong result or panics. If
|
|
/// debug assertions are enabled, a panic is guaranteed.
|
|
///
|
|
/// # Panics
|
|
///
|
|
/// The returned iterator might panic if the to-be-returned index would
|
|
/// overflow a [`usize`].
|
|
///
|
|
/// [`usize::MAX`]: ../../std/usize/constant.MAX.html
|
|
/// [`usize`]: ../../std/primitive.usize.html
|
|
/// [`zip()`]: #method.zip
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// ```
|
|
/// let a = ['a', 'b', 'c'];
|
|
///
|
|
/// let mut iter = a.iter().enumerate();
|
|
///
|
|
/// assert_eq!(iter.next(), Some((0, &'a')));
|
|
/// assert_eq!(iter.next(), Some((1, &'b')));
|
|
/// assert_eq!(iter.next(), Some((2, &'c')));
|
|
/// assert_eq!(iter.next(), 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 which can use `peek` to look at the next element of
|
|
/// the iterator without consuming it.
|
|
///
|
|
/// Adds a [`peek()`] method to an iterator. See its documentation for
|
|
/// more information.
|
|
///
|
|
/// Note that the underlying iterator is still advanced when [`peek()`] is
|
|
/// called for the first time: In order to retrieve the next element,
|
|
/// [`next()`] is called on the underlying iterator, hence any side effects of
|
|
/// the [`next()`] method will occur.
|
|
///
|
|
/// [`peek()`]: struct.Peekable.html#method.peek
|
|
/// [`next()`]: ../../std/iter/trait.Iterator.html#tymethod.next
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// Basic usage:
|
|
///
|
|
/// ```
|
|
/// let xs = [1, 2, 3];
|
|
///
|
|
/// let mut iter = xs.iter().peekable();
|
|
///
|
|
/// // peek() lets us see into the future
|
|
/// assert_eq!(iter.peek(), Some(&&1));
|
|
/// assert_eq!(iter.next(), Some(&1));
|
|
///
|
|
/// assert_eq!(iter.next(), Some(&2));
|
|
///
|
|
/// // we can peek() multiple times, the iterator won't advance
|
|
/// assert_eq!(iter.peek(), Some(&&3));
|
|
/// assert_eq!(iter.peek(), Some(&&3));
|
|
///
|
|
/// assert_eq!(iter.next(), Some(&3));
|
|
///
|
|
/// // after the iterator is finished, so is peek()
|
|
/// assert_eq!(iter.peek(), None);
|
|
/// assert_eq!(iter.next(), 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 [`skip()`]s elements based on a predicate.
|
|
///
|
|
/// [`skip()`]: #method.skip
|
|
///
|
|
/// `skip_while()` takes a closure as an argument. It will call this
|
|
/// closure on each element of the iterator, and ignore elements
|
|
/// until it returns `false`.
|
|
///
|
|
/// After `false` is returned, `skip_while()`'s job is over, and the
|
|
/// rest of the elements are yielded.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// Basic usage:
|
|
///
|
|
/// ```
|
|
/// let a = [-1i32, 0, 1];
|
|
///
|
|
/// let mut iter = a.into_iter().skip_while(|x| x.is_negative());
|
|
///
|
|
/// assert_eq!(iter.next(), Some(&0));
|
|
/// assert_eq!(iter.next(), Some(&1));
|
|
/// assert_eq!(iter.next(), None);
|
|
/// ```
|
|
///
|
|
/// Because the closure passed to `skip_while()` takes a reference, and many
|
|
/// iterators iterate over references, this leads to a possibly confusing
|
|
/// situation, where the type of the closure is a double reference:
|
|
///
|
|
/// ```
|
|
/// let a = [-1, 0, 1];
|
|
///
|
|
/// let mut iter = a.into_iter().skip_while(|x| **x < 0); // need two *s!
|
|
///
|
|
/// assert_eq!(iter.next(), Some(&0));
|
|
/// assert_eq!(iter.next(), Some(&1));
|
|
/// assert_eq!(iter.next(), None);
|
|
/// ```
|
|
///
|
|
/// Stopping after an initial `false`:
|
|
///
|
|
/// ```
|
|
/// let a = [-1, 0, 1, -2];
|
|
///
|
|
/// let mut iter = a.into_iter().skip_while(|x| **x < 0);
|
|
///
|
|
/// assert_eq!(iter.next(), Some(&0));
|
|
/// assert_eq!(iter.next(), Some(&1));
|
|
///
|
|
/// // while this would have been false, since we already got a false,
|
|
/// // skip_while() isn't used any more
|
|
/// assert_eq!(iter.next(), Some(&-2));
|
|
///
|
|
/// assert_eq!(iter.next(), 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 based on a predicate.
|
|
///
|
|
/// `take_while()` takes a closure as an argument. It will call this
|
|
/// closure on each element of the iterator, and yield elements
|
|
/// while it returns `true`.
|
|
///
|
|
/// After `false` is returned, `take_while()`'s job is over, and the
|
|
/// rest of the elements are ignored.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// Basic usage:
|
|
///
|
|
/// ```
|
|
/// let a = [-1i32, 0, 1];
|
|
///
|
|
/// let mut iter = a.into_iter().take_while(|x| x.is_negative());
|
|
///
|
|
/// assert_eq!(iter.next(), Some(&-1));
|
|
/// assert_eq!(iter.next(), None);
|
|
/// ```
|
|
///
|
|
/// Because the closure passed to `take_while()` takes a reference, and many
|
|
/// iterators iterate over references, this leads to a possibly confusing
|
|
/// situation, where the type of the closure is a double reference:
|
|
///
|
|
/// ```
|
|
/// let a = [-1, 0, 1];
|
|
///
|
|
/// let mut iter = a.into_iter().take_while(|x| **x < 0); // need two *s!
|
|
///
|
|
/// assert_eq!(iter.next(), Some(&-1));
|
|
/// assert_eq!(iter.next(), None);
|
|
/// ```
|
|
///
|
|
/// Stopping after an initial `false`:
|
|
///
|
|
/// ```
|
|
/// let a = [-1, 0, 1, -2];
|
|
///
|
|
/// let mut iter = a.into_iter().take_while(|x| **x < 0);
|
|
///
|
|
/// assert_eq!(iter.next(), Some(&-1));
|
|
///
|
|
/// // We have more elements that are less than zero, but since we already
|
|
/// // got a false, take_while() isn't used any more
|
|
/// assert_eq!(iter.next(), None);
|
|
/// ```
|
|
///
|
|
/// Because `take_while()` needs to look at the value in order to see if it
|
|
/// should be included or not, consuming iterators will see that it is
|
|
/// removed:
|
|
///
|
|
/// ```
|
|
/// let a = [1, 2, 3, 4];
|
|
/// let mut iter = a.into_iter();
|
|
///
|
|
/// let result: Vec<i32> = iter.by_ref()
|
|
/// .take_while(|n| **n != 3)
|
|
/// .cloned()
|
|
/// .collect();
|
|
///
|
|
/// assert_eq!(result, &[1, 2]);
|
|
///
|
|
/// let result: Vec<i32> = iter.cloned().collect();
|
|
///
|
|
/// assert_eq!(result, &[4]);
|
|
/// ```
|
|
///
|
|
/// The `3` is no longer there, because it was consumed in order to see if
|
|
/// the iteration should stop, but wasn't placed back into the iterator or
|
|
/// some similar thing.
|
|
#[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.
|
|
///
|
|
/// After they have been consumed, the rest of the elements are yielded.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// Basic usage:
|
|
///
|
|
/// ```
|
|
/// let a = [1, 2, 3];
|
|
///
|
|
/// let mut iter = a.iter().skip(2);
|
|
///
|
|
/// assert_eq!(iter.next(), Some(&3));
|
|
/// assert_eq!(iter.next(), 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 its first `n` elements.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// Basic usage:
|
|
///
|
|
/// ```
|
|
/// let a = [1, 2, 3];
|
|
///
|
|
/// let mut iter = a.iter().take(2);
|
|
///
|
|
/// assert_eq!(iter.next(), Some(&1));
|
|
/// assert_eq!(iter.next(), Some(&2));
|
|
/// assert_eq!(iter.next(), None);
|
|
/// ```
|
|
///
|
|
/// `take()` is often used with an infinite iterator, to make it finite:
|
|
///
|
|
/// ```
|
|
/// let mut iter = (0..).take(3);
|
|
///
|
|
/// assert_eq!(iter.next(), Some(0));
|
|
/// assert_eq!(iter.next(), Some(1));
|
|
/// assert_eq!(iter.next(), Some(2));
|
|
/// assert_eq!(iter.next(), None);
|
|
/// ```
|
|
#[inline]
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
fn take(self, n: usize) -> Take<Self> where Self: Sized, {
|
|
Take{iter: self, n: n}
|
|
}
|
|
|
|
/// An iterator adaptor similar to [`fold()`] that holds internal state and
|
|
/// produces a new iterator.
|
|
///
|
|
/// [`fold()`]: #method.fold
|
|
///
|
|
/// `scan()` takes two arguments: an initial value which seeds the internal
|
|
/// state, and a closure with two arguments, the first being a mutable
|
|
/// reference to the internal state and the second an iterator element.
|
|
/// The closure can assign to the internal state to share state between
|
|
/// iterations.
|
|
///
|
|
/// On iteration, the closure will be applied to each element of the
|
|
/// iterator and the return value from the closure, an [`Option`], is
|
|
/// yielded by the iterator.
|
|
///
|
|
/// [`Option`]: ../../std/option/enum.Option.html
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// Basic usage:
|
|
///
|
|
/// ```
|
|
/// let a = [1, 2, 3];
|
|
///
|
|
/// let mut iter = a.iter().scan(1, |state, &x| {
|
|
/// // each iteration, we'll multiply the state by the element
|
|
/// *state = *state * x;
|
|
///
|
|
/// // the value passed on to the next iteration
|
|
/// Some(*state)
|
|
/// });
|
|
///
|
|
/// assert_eq!(iter.next(), Some(1));
|
|
/// assert_eq!(iter.next(), Some(2));
|
|
/// assert_eq!(iter.next(), Some(6));
|
|
/// assert_eq!(iter.next(), 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 works like map, but flattens nested structure.
|
|
///
|
|
/// The [`map()`] adapter is very useful, but only when the closure
|
|
/// argument produces values. If it produces an iterator instead, there's
|
|
/// an extra layer of indirection. `flat_map()` will remove this extra layer
|
|
/// on its own.
|
|
///
|
|
/// Another way of thinking about `flat_map()`: [`map()`]'s closure returns
|
|
/// one item for each element, and `flat_map()`'s closure returns an
|
|
/// iterator for each element.
|
|
///
|
|
/// [`map()`]: #method.map
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// Basic usage:
|
|
///
|
|
/// ```
|
|
/// let words = ["alpha", "beta", "gamma"];
|
|
///
|
|
/// // chars() returns an iterator
|
|
/// let merged: String = words.iter()
|
|
/// .flat_map(|s| s.chars())
|
|
/// .collect();
|
|
/// assert_eq!(merged, "alphabetagamma");
|
|
/// ```
|
|
#[inline]
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
fn flat_map<U, F>(self, f: F) -> FlatMap<Self, U, F>
|
|
where Self: Sized, U: IntoIterator, F: FnMut(Self::Item) -> U,
|
|
{
|
|
FlatMap{iter: self, f: f, frontiter: None, backiter: None }
|
|
}
|
|
|
|
/// Creates an iterator which ends after the first [`None`].
|
|
///
|
|
/// After an iterator returns [`None`], future calls may or may not yield
|
|
/// [`Some(T)`] again. `fuse()` adapts an iterator, ensuring that after a
|
|
/// [`None`] is given, it will always return [`None`] forever.
|
|
///
|
|
/// [`None`]: ../../std/option/enum.Option.html#variant.None
|
|
/// [`Some(T)`]: ../../std/option/enum.Option.html#variant.Some
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// Basic usage:
|
|
///
|
|
/// ```
|
|
/// // an iterator which alternates between Some and None
|
|
/// struct Alternate {
|
|
/// state: i32,
|
|
/// }
|
|
///
|
|
/// impl Iterator for Alternate {
|
|
/// type Item = i32;
|
|
///
|
|
/// fn next(&mut self) -> Option<i32> {
|
|
/// let val = self.state;
|
|
/// self.state = self.state + 1;
|
|
///
|
|
/// // if it's even, Some(i32), else None
|
|
/// if val % 2 == 0 {
|
|
/// Some(val)
|
|
/// } else {
|
|
/// None
|
|
/// }
|
|
/// }
|
|
/// }
|
|
///
|
|
/// let mut iter = Alternate { state: 0 };
|
|
///
|
|
/// // we can see our iterator going back and forth
|
|
/// assert_eq!(iter.next(), Some(0));
|
|
/// assert_eq!(iter.next(), None);
|
|
/// assert_eq!(iter.next(), Some(2));
|
|
/// assert_eq!(iter.next(), None);
|
|
///
|
|
/// // however, once we fuse it...
|
|
/// let mut iter = iter.fuse();
|
|
///
|
|
/// assert_eq!(iter.next(), Some(4));
|
|
/// assert_eq!(iter.next(), None);
|
|
///
|
|
/// // it will always return None after the first time.
|
|
/// assert_eq!(iter.next(), None);
|
|
/// assert_eq!(iter.next(), None);
|
|
/// assert_eq!(iter.next(), None);
|
|
/// ```
|
|
#[inline]
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
fn fuse(self) -> Fuse<Self> where Self: Sized {
|
|
Fuse{iter: self, done: false}
|
|
}
|
|
|
|
/// Do something with each element of an iterator, passing the value on.
|
|
///
|
|
/// When using iterators, you'll often chain several of them together.
|
|
/// While working on such code, you might want to check out what's
|
|
/// happening at various parts in the pipeline. To do that, insert
|
|
/// a call to `inspect()`.
|
|
///
|
|
/// It's much more common for `inspect()` to be used as a debugging tool
|
|
/// than to exist in your final code, but never say never.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// Basic usage:
|
|
///
|
|
/// ```
|
|
/// let a = [1, 4, 2, 3];
|
|
///
|
|
/// // this iterator sequence is complex.
|
|
/// let sum = a.iter()
|
|
/// .cloned()
|
|
/// .filter(|&x| x % 2 == 0)
|
|
/// .fold(0, |sum, i| sum + i);
|
|
///
|
|
/// println!("{}", sum);
|
|
///
|
|
/// // let's add some inspect() calls to investigate what's happening
|
|
/// let sum = a.iter()
|
|
/// .cloned()
|
|
/// .inspect(|x| println!("about to filter: {}", x))
|
|
/// .filter(|&x| x % 2 == 0)
|
|
/// .inspect(|x| println!("made it through filter: {}", x))
|
|
/// .fold(0, |sum, i| sum + i);
|
|
///
|
|
/// println!("{}", sum);
|
|
/// ```
|
|
///
|
|
/// This will print:
|
|
///
|
|
/// ```text
|
|
/// about to filter: 1
|
|
/// about to filter: 4
|
|
/// made it through filter: 4
|
|
/// about to filter: 2
|
|
/// made it through filter: 2
|
|
/// about to filter: 3
|
|
/// 6
|
|
/// ```
|
|
#[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}
|
|
}
|
|
|
|
/// Borrows an iterator, rather than consuming it.
|
|
///
|
|
/// This is useful to allow applying iterator adaptors while still
|
|
/// retaining ownership of the original iterator.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// Basic usage:
|
|
///
|
|
/// ```
|
|
/// let a = [1, 2, 3];
|
|
///
|
|
/// let iter = a.into_iter();
|
|
///
|
|
/// let sum: i32 = iter.take(5)
|
|
/// .fold(0, |acc, &i| acc + i );
|
|
///
|
|
/// assert_eq!(sum, 6);
|
|
///
|
|
/// // if we try to use iter again, it won't work. The following line
|
|
/// // gives "error: use of moved value: `iter`
|
|
/// // assert_eq!(iter.next(), None);
|
|
///
|
|
/// // let's try that again
|
|
/// let a = [1, 2, 3];
|
|
///
|
|
/// let mut iter = a.into_iter();
|
|
///
|
|
/// // instead, we add in a .by_ref()
|
|
/// let sum: i32 = iter.by_ref()
|
|
/// .take(2)
|
|
/// .fold(0, |acc, &i| acc + i );
|
|
///
|
|
/// assert_eq!(sum, 3);
|
|
///
|
|
/// // now this is just fine:
|
|
/// assert_eq!(iter.next(), Some(&3));
|
|
/// assert_eq!(iter.next(), None);
|
|
/// ```
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
fn by_ref(&mut self) -> &mut Self where Self: Sized { self }
|
|
|
|
/// Transforms an iterator into a collection.
|
|
///
|
|
/// `collect()` can take anything iterable, and turn it into a relevant
|
|
/// collection. This is one of the more powerful methods in the standard
|
|
/// library, used in a variety of contexts.
|
|
///
|
|
/// The most basic pattern in which `collect()` is used is to turn one
|
|
/// collection into another. You take a collection, call [`iter()`] on it,
|
|
/// do a bunch of transformations, and then `collect()` at the end.
|
|
///
|
|
/// One of the keys to `collect()`'s power is that many things you might
|
|
/// not think of as 'collections' actually are. For example, a [`String`]
|
|
/// is a collection of [`char`]s. And a collection of
|
|
/// [`Result<T, E>`][`Result`] can be thought of as single
|
|
/// [`Result`]`<Collection<T>, E>`. See the examples below for more.
|
|
///
|
|
/// Because `collect()` is so general, it can cause problems with type
|
|
/// inference. As such, `collect()` is one of the few times you'll see
|
|
/// the syntax affectionately known as the 'turbofish': `::<>`. This
|
|
/// helps the inference algorithm understand specifically which collection
|
|
/// you're trying to collect into.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// Basic usage:
|
|
///
|
|
/// ```
|
|
/// let a = [1, 2, 3];
|
|
///
|
|
/// let doubled: Vec<i32> = a.iter()
|
|
/// .map(|&x| x * 2)
|
|
/// .collect();
|
|
///
|
|
/// assert_eq!(vec![2, 4, 6], doubled);
|
|
/// ```
|
|
///
|
|
/// Note that we needed the `: Vec<i32>` on the left-hand side. This is because
|
|
/// we could collect into, for example, a [`VecDeque<T>`] instead:
|
|
///
|
|
/// [`VecDeque<T>`]: ../../std/collections/struct.VecDeque.html
|
|
///
|
|
/// ```
|
|
/// use std::collections::VecDeque;
|
|
///
|
|
/// let a = [1, 2, 3];
|
|
///
|
|
/// let doubled: VecDeque<i32> = a.iter()
|
|
/// .map(|&x| x * 2)
|
|
/// .collect();
|
|
///
|
|
/// assert_eq!(2, doubled[0]);
|
|
/// assert_eq!(4, doubled[1]);
|
|
/// assert_eq!(6, doubled[2]);
|
|
/// ```
|
|
///
|
|
/// Using the 'turbofish' instead of annotating `doubled`:
|
|
///
|
|
/// ```
|
|
/// let a = [1, 2, 3];
|
|
///
|
|
/// let doubled = a.iter()
|
|
/// .map(|&x| x * 2)
|
|
/// .collect::<Vec<i32>>();
|
|
///
|
|
/// assert_eq!(vec![2, 4, 6], doubled);
|
|
/// ```
|
|
///
|
|
/// Because `collect()` cares about what you're collecting into, you can
|
|
/// still use a partial type hint, `_`, with the turbofish:
|
|
///
|
|
/// ```
|
|
/// let a = [1, 2, 3];
|
|
///
|
|
/// let doubled = a.iter()
|
|
/// .map(|&x| x * 2)
|
|
/// .collect::<Vec<_>>();
|
|
///
|
|
/// assert_eq!(vec![2, 4, 6], doubled);
|
|
/// ```
|
|
///
|
|
/// Using `collect()` to make a [`String`]:
|
|
///
|
|
/// ```
|
|
/// let chars = ['g', 'd', 'k', 'k', 'n'];
|
|
///
|
|
/// let hello: String = chars.iter()
|
|
/// .map(|&x| x as u8)
|
|
/// .map(|x| (x + 1) as char)
|
|
/// .collect();
|
|
///
|
|
/// assert_eq!("hello", hello);
|
|
/// ```
|
|
///
|
|
/// If you have a list of [`Result<T, E>`][`Result`]s, you can use `collect()` to
|
|
/// see if any of them failed:
|
|
///
|
|
/// ```
|
|
/// let results = [Ok(1), Err("nope"), Ok(3), Err("bad")];
|
|
///
|
|
/// let result: Result<Vec<_>, &str> = results.iter().cloned().collect();
|
|
///
|
|
/// // gives us the first error
|
|
/// assert_eq!(Err("nope"), result);
|
|
///
|
|
/// let results = [Ok(1), Ok(3)];
|
|
///
|
|
/// let result: Result<Vec<_>, &str> = results.iter().cloned().collect();
|
|
///
|
|
/// // gives us the list of answers
|
|
/// assert_eq!(Ok(vec![1, 3]), result);
|
|
/// ```
|
|
///
|
|
/// [`iter()`]: ../../std/iter/trait.Iterator.html#tymethod.next
|
|
/// [`String`]: ../../std/string/struct.String.html
|
|
/// [`char`]: ../../std/primitive.char.html
|
|
/// [`Result`]: ../../std/result/enum.Result.html
|
|
#[inline]
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
fn collect<B: FromIterator<Self::Item>>(self) -> B where Self: Sized {
|
|
FromIterator::from_iter(self)
|
|
}
|
|
|
|
/// Consumes an iterator, creating two collections from it.
|
|
///
|
|
/// The predicate passed to `partition()` can return `true`, or `false`.
|
|
/// `partition()` returns a pair, all of the elements for which it returned
|
|
/// `true`, and all of the elements for which it returned `false`.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// Basic usage:
|
|
///
|
|
/// ```
|
|
/// let a = [1, 2, 3];
|
|
///
|
|
/// let (even, odd): (Vec<i32>, Vec<i32>) = a.into_iter()
|
|
/// .partition(|&n| n % 2 == 0);
|
|
///
|
|
/// assert_eq!(even, vec![2]);
|
|
/// assert_eq!(odd, vec![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))
|
|
} else {
|
|
right.extend(Some(x))
|
|
}
|
|
}
|
|
|
|
(left, right)
|
|
}
|
|
|
|
/// An iterator adaptor that applies a function, producing a single, final value.
|
|
///
|
|
/// `fold()` takes two arguments: an initial value, and a closure with two
|
|
/// arguments: an 'accumulator', and an element. The closure returns the value that
|
|
/// the accumulator should have for the next iteration.
|
|
///
|
|
/// The initial value is the value the accumulator will have on the first
|
|
/// call.
|
|
///
|
|
/// After applying this closure to every element of the iterator, `fold()`
|
|
/// returns the accumulator.
|
|
///
|
|
/// This operation is sometimes called 'reduce' or 'inject'.
|
|
///
|
|
/// Folding is useful whenever you have a collection of something, and want
|
|
/// to produce a single value from it.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// Basic usage:
|
|
///
|
|
/// ```
|
|
/// let a = [1, 2, 3];
|
|
///
|
|
/// // the sum of all of the elements of a
|
|
/// let sum = a.iter()
|
|
/// .fold(0, |acc, &x| acc + x);
|
|
///
|
|
/// assert_eq!(sum, 6);
|
|
/// ```
|
|
///
|
|
/// Let's walk through each step of the iteration here:
|
|
///
|
|
/// | element | acc | x | result |
|
|
/// |---------|-----|---|--------|
|
|
/// | | 0 | | |
|
|
/// | 1 | 0 | 1 | 1 |
|
|
/// | 2 | 1 | 2 | 3 |
|
|
/// | 3 | 3 | 3 | 6 |
|
|
///
|
|
/// And so, our final result, `6`.
|
|
///
|
|
/// It's common for people who haven't used iterators a lot to
|
|
/// use a `for` loop with a list of things to build up a result. Those
|
|
/// can be turned into `fold()`s:
|
|
///
|
|
/// [`for`]: ../../book/loops.html#for
|
|
///
|
|
/// ```
|
|
/// let numbers = [1, 2, 3, 4, 5];
|
|
///
|
|
/// let mut result = 0;
|
|
///
|
|
/// // for loop:
|
|
/// for i in &numbers {
|
|
/// result = result + i;
|
|
/// }
|
|
///
|
|
/// // fold:
|
|
/// let result2 = numbers.iter().fold(0, |acc, &x| acc + x);
|
|
///
|
|
/// // they're the same
|
|
/// assert_eq!(result, result2);
|
|
/// ```
|
|
#[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 if every element of the iterator matches a predicate.
|
|
///
|
|
/// `all()` takes a closure that returns `true` or `false`. It applies
|
|
/// this closure to each element of the iterator, and if they all return
|
|
/// `true`, then so does `all()`. If any of them return `false`, it
|
|
/// returns `false`.
|
|
///
|
|
/// `all()` is short-circuiting; in other words, it will stop processing
|
|
/// as soon as it finds a `false`, given that no matter what else happens,
|
|
/// the result will also be `false`.
|
|
///
|
|
/// An empty iterator returns `true`.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// Basic usage:
|
|
///
|
|
/// ```
|
|
/// let a = [1, 2, 3];
|
|
///
|
|
/// assert!(a.iter().all(|&x| x > 0));
|
|
///
|
|
/// assert!(!a.iter().all(|&x| x > 2));
|
|
/// ```
|
|
///
|
|
/// Stopping at the first `false`:
|
|
///
|
|
/// ```
|
|
/// let a = [1, 2, 3];
|
|
///
|
|
/// let mut iter = a.iter();
|
|
///
|
|
/// assert!(!iter.all(|&x| x != 2));
|
|
///
|
|
/// // we can still use `iter`, as there are more elements.
|
|
/// assert_eq!(iter.next(), Some(&3));
|
|
/// ```
|
|
#[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 {
|
|
if !f(x) {
|
|
return false;
|
|
}
|
|
}
|
|
true
|
|
}
|
|
|
|
/// Tests if any element of the iterator matches a predicate.
|
|
///
|
|
/// `any()` takes a closure that returns `true` or `false`. It applies
|
|
/// this closure to each element of the iterator, and if any of them return
|
|
/// `true`, then so does `any()`. If they all return `false`, it
|
|
/// returns `false`.
|
|
///
|
|
/// `any()` is short-circuiting; in other words, it will stop processing
|
|
/// as soon as it finds a `true`, given that no matter what else happens,
|
|
/// the result will also be `true`.
|
|
///
|
|
/// An empty iterator returns `false`.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// Basic usage:
|
|
///
|
|
/// ```
|
|
/// let a = [1, 2, 3];
|
|
///
|
|
/// assert!(a.iter().any(|&x| x > 0));
|
|
///
|
|
/// assert!(!a.iter().any(|&x| x > 5));
|
|
/// ```
|
|
///
|
|
/// Stopping at the first `true`:
|
|
///
|
|
/// ```
|
|
/// let a = [1, 2, 3];
|
|
///
|
|
/// let mut iter = a.iter();
|
|
///
|
|
/// assert!(iter.any(|&x| x != 2));
|
|
///
|
|
/// // we can still use `iter`, as there are more elements.
|
|
/// assert_eq!(iter.next(), Some(&2));
|
|
/// ```
|
|
#[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 {
|
|
if f(x) {
|
|
return true;
|
|
}
|
|
}
|
|
false
|
|
}
|
|
|
|
/// Searches for an element of an iterator that satisfies a predicate.
|
|
///
|
|
/// `find()` takes a closure that returns `true` or `false`. It applies
|
|
/// this closure to each element of the iterator, and if any of them return
|
|
/// `true`, then `find()` returns [`Some(element)`]. If they all return
|
|
/// `false`, it returns [`None`].
|
|
///
|
|
/// `find()` is short-circuiting; in other words, it will stop processing
|
|
/// as soon as the closure returns `true`.
|
|
///
|
|
/// Because `find()` takes a reference, and many iterators iterate over
|
|
/// references, this leads to a possibly confusing situation where the
|
|
/// argument is a double reference. You can see this effect in the
|
|
/// examples below, with `&&x`.
|
|
///
|
|
/// [`Some(element)`]: ../../std/option/enum.Option.html#variant.Some
|
|
/// [`None`]: ../../std/option/enum.Option.html#variant.None
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// Basic usage:
|
|
///
|
|
/// ```
|
|
/// let a = [1, 2, 3];
|
|
///
|
|
/// assert_eq!(a.iter().find(|&&x| x == 2), Some(&2));
|
|
///
|
|
/// assert_eq!(a.iter().find(|&&x| x == 5), None);
|
|
/// ```
|
|
///
|
|
/// Stopping at the first `true`:
|
|
///
|
|
/// ```
|
|
/// let a = [1, 2, 3];
|
|
///
|
|
/// let mut iter = a.iter();
|
|
///
|
|
/// assert_eq!(iter.find(|&&x| x == 2), Some(&2));
|
|
///
|
|
/// // we can still use `iter`, as there are more elements.
|
|
/// assert_eq!(iter.next(), Some(&3));
|
|
/// ```
|
|
#[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 {
|
|
if predicate(&x) { return Some(x) }
|
|
}
|
|
None
|
|
}
|
|
|
|
/// Searches for an element in an iterator, returning its index.
|
|
///
|
|
/// `position()` takes a closure that returns `true` or `false`. It applies
|
|
/// this closure to each element of the iterator, and if one of them
|
|
/// returns `true`, then `position()` returns [`Some(index)`]. If all of
|
|
/// them return `false`, it returns [`None`].
|
|
///
|
|
/// `position()` is short-circuiting; in other words, it will stop
|
|
/// processing as soon as it finds a `true`.
|
|
///
|
|
/// # Overflow Behavior
|
|
///
|
|
/// The method does no guarding against overflows, so if there are more
|
|
/// than [`usize::MAX`] non-matching elements, it either produces the wrong
|
|
/// result or panics. If debug assertions are enabled, a panic is
|
|
/// guaranteed.
|
|
///
|
|
/// # Panics
|
|
///
|
|
/// This function might panic if the iterator has more than `usize::MAX`
|
|
/// non-matching elements.
|
|
///
|
|
/// [`Some(index)`]: ../../std/option/enum.Option.html#variant.Some
|
|
/// [`None`]: ../../std/option/enum.Option.html#variant.None
|
|
/// [`usize::MAX`]: ../../std/usize/constant.MAX.html
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// Basic usage:
|
|
///
|
|
/// ```
|
|
/// let a = [1, 2, 3];
|
|
///
|
|
/// assert_eq!(a.iter().position(|&x| x == 2), Some(1));
|
|
///
|
|
/// assert_eq!(a.iter().position(|&x| x == 5), None);
|
|
/// ```
|
|
///
|
|
/// Stopping at the first `true`:
|
|
///
|
|
/// ```
|
|
/// let a = [1, 2, 3];
|
|
///
|
|
/// let mut iter = a.iter();
|
|
///
|
|
/// assert_eq!(iter.position(|&x| x == 2), Some(1));
|
|
///
|
|
/// // we can still use `iter`, as there are more elements.
|
|
/// assert_eq!(iter.next(), Some(&3));
|
|
/// ```
|
|
#[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,
|
|
{
|
|
// `enumerate` might overflow.
|
|
for (i, x) in self.enumerate() {
|
|
if predicate(x) {
|
|
return Some(i);
|
|
}
|
|
}
|
|
None
|
|
}
|
|
|
|
/// Searches for an element in an iterator from the right, returning its
|
|
/// index.
|
|
///
|
|
/// `rposition()` takes a closure that returns `true` or `false`. It applies
|
|
/// this closure to each element of the iterator, starting from the end,
|
|
/// and if one of them returns `true`, then `rposition()` returns
|
|
/// [`Some(index)`]. If all of them return `false`, it returns [`None`].
|
|
///
|
|
/// `rposition()` is short-circuiting; in other words, it will stop
|
|
/// processing as soon as it finds a `true`.
|
|
///
|
|
/// [`Some(index)`]: ../../std/option/enum.Option.html#variant.Some
|
|
/// [`None`]: ../../std/option/enum.Option.html#variant.None
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// Basic usage:
|
|
///
|
|
/// ```
|
|
/// let a = [1, 2, 3];
|
|
///
|
|
/// assert_eq!(a.iter().rposition(|&x| x == 3), Some(2));
|
|
///
|
|
/// assert_eq!(a.iter().rposition(|&x| x == 5), None);
|
|
/// ```
|
|
///
|
|
/// Stopping at the first `true`:
|
|
///
|
|
/// ```
|
|
/// let a = [1, 2, 3];
|
|
///
|
|
/// let mut iter = a.iter();
|
|
///
|
|
/// assert_eq!(iter.rposition(|&x| x == 2), Some(1));
|
|
///
|
|
/// // we can still use `iter`, as there are more elements.
|
|
/// assert_eq!(iter.next(), Some(&1));
|
|
/// ```
|
|
#[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() {
|
|
// No need for an overflow check here, because `ExactSizeIterator`
|
|
// implies that the number of elements fits into a `usize`.
|
|
i -= 1;
|
|
if predicate(v) {
|
|
return Some(i);
|
|
}
|
|
}
|
|
None
|
|
}
|
|
|
|
/// Returns the maximum element of an iterator.
|
|
///
|
|
/// If several elements are equally maximum, the last element is
|
|
/// returned. If the iterator is empty, [`None`] is returned.
|
|
///
|
|
/// [`None`]: ../../std/option/enum.Option.html#variant.None
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// Basic usage:
|
|
///
|
|
/// ```
|
|
/// let a = [1, 2, 3];
|
|
/// let b: Vec<u32> = Vec::new();
|
|
///
|
|
/// assert_eq!(a.iter().max(), Some(&3));
|
|
/// assert_eq!(b.iter().max(), None);
|
|
/// ```
|
|
#[inline]
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
fn max(self) -> Option<Self::Item> where Self: Sized, Self::Item: Ord
|
|
{
|
|
select_fold1(self,
|
|
|_| (),
|
|
// switch to y even if it is only equal, to preserve
|
|
// stability.
|
|
|_, x, _, y| *x <= *y)
|
|
.map(|(_, x)| x)
|
|
}
|
|
|
|
/// Returns the minimum element of an iterator.
|
|
///
|
|
/// If several elements are equally minimum, the first element is
|
|
/// returned. If the iterator is empty, [`None`] is returned.
|
|
///
|
|
/// [`None`]: ../../std/option/enum.Option.html#variant.None
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// Basic usage:
|
|
///
|
|
/// ```
|
|
/// let a = [1, 2, 3];
|
|
/// let b: Vec<u32> = Vec::new();
|
|
///
|
|
/// assert_eq!(a.iter().min(), Some(&1));
|
|
/// assert_eq!(b.iter().min(), None);
|
|
/// ```
|
|
#[inline]
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
fn min(self) -> Option<Self::Item> where Self: Sized, Self::Item: Ord
|
|
{
|
|
select_fold1(self,
|
|
|_| (),
|
|
// only switch to y if it is strictly smaller, to
|
|
// preserve stability.
|
|
|_, x, _, y| *x > *y)
|
|
.map(|(_, x)| x)
|
|
}
|
|
|
|
/// Returns the element that gives the maximum value from the
|
|
/// specified function.
|
|
///
|
|
/// If several elements are equally maximum, the last element is
|
|
/// returned. If the iterator is empty, [`None`] is returned.
|
|
///
|
|
/// [`None`]: ../../std/option/enum.Option.html#variant.None
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// ```
|
|
/// let a = [-3_i32, 0, 1, 5, -10];
|
|
/// assert_eq!(*a.iter().max_by_key(|x| x.abs()).unwrap(), -10);
|
|
/// ```
|
|
#[inline]
|
|
#[stable(feature = "iter_cmp_by_key", since = "1.6.0")]
|
|
fn max_by_key<B: Ord, F>(self, f: F) -> Option<Self::Item>
|
|
where Self: Sized, F: FnMut(&Self::Item) -> B,
|
|
{
|
|
select_fold1(self,
|
|
f,
|
|
// switch to y even if it is only equal, to preserve
|
|
// stability.
|
|
|x_p, _, y_p, _| x_p <= y_p)
|
|
.map(|(_, x)| x)
|
|
}
|
|
|
|
/// Returns the element that gives the maximum value with respect to the
|
|
/// specified comparison function.
|
|
///
|
|
/// If several elements are equally maximum, the last element is
|
|
/// returned. If the iterator is empty, [`None`] is returned.
|
|
///
|
|
/// [`None`]: ../../std/option/enum.Option.html#variant.None
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// ```
|
|
/// let a = [-3_i32, 0, 1, 5, -10];
|
|
/// assert_eq!(*a.iter().max_by(|x, y| x.cmp(y)).unwrap(), 5);
|
|
/// ```
|
|
#[inline]
|
|
#[stable(feature = "iter_max_by", since = "1.15.0")]
|
|
fn max_by<F>(self, mut compare: F) -> Option<Self::Item>
|
|
where Self: Sized, F: FnMut(&Self::Item, &Self::Item) -> Ordering,
|
|
{
|
|
select_fold1(self,
|
|
|_| (),
|
|
// switch to y even if it is only equal, to preserve
|
|
// stability.
|
|
|_, x, _, y| Ordering::Greater != compare(x, y))
|
|
.map(|(_, x)| x)
|
|
}
|
|
|
|
/// Returns the element that gives the minimum value from the
|
|
/// specified function.
|
|
///
|
|
/// If several elements are equally minimum, the first element is
|
|
/// returned. If the iterator is empty, [`None`] is returned.
|
|
///
|
|
/// [`None`]: ../../std/option/enum.Option.html#variant.None
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// ```
|
|
/// let a = [-3_i32, 0, 1, 5, -10];
|
|
/// assert_eq!(*a.iter().min_by_key(|x| x.abs()).unwrap(), 0);
|
|
/// ```
|
|
#[stable(feature = "iter_cmp_by_key", since = "1.6.0")]
|
|
fn min_by_key<B: Ord, F>(self, f: F) -> Option<Self::Item>
|
|
where Self: Sized, F: FnMut(&Self::Item) -> B,
|
|
{
|
|
select_fold1(self,
|
|
f,
|
|
// only switch to y if it is strictly smaller, to
|
|
// preserve stability.
|
|
|x_p, _, y_p, _| x_p > y_p)
|
|
.map(|(_, x)| x)
|
|
}
|
|
|
|
/// Returns the element that gives the minimum value with respect to the
|
|
/// specified comparison function.
|
|
///
|
|
/// If several elements are equally minimum, the first element is
|
|
/// returned. If the iterator is empty, [`None`] is returned.
|
|
///
|
|
/// [`None`]: ../../std/option/enum.Option.html#variant.None
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// ```
|
|
/// let a = [-3_i32, 0, 1, 5, -10];
|
|
/// assert_eq!(*a.iter().min_by(|x, y| x.cmp(y)).unwrap(), -10);
|
|
/// ```
|
|
#[inline]
|
|
#[stable(feature = "iter_min_by", since = "1.15.0")]
|
|
fn min_by<F>(self, mut compare: F) -> Option<Self::Item>
|
|
where Self: Sized, F: FnMut(&Self::Item, &Self::Item) -> Ordering,
|
|
{
|
|
select_fold1(self,
|
|
|_| (),
|
|
// switch to y even if it is strictly smaller, to
|
|
// preserve stability.
|
|
|_, x, _, y| Ordering::Greater == compare(x, y))
|
|
.map(|(_, x)| x)
|
|
}
|
|
|
|
|
|
/// Reverses an iterator's direction.
|
|
///
|
|
/// Usually, iterators iterate from left to right. After using `rev()`,
|
|
/// an iterator will instead iterate from right to left.
|
|
///
|
|
/// This is only possible if the iterator has an end, so `rev()` only
|
|
/// works on [`DoubleEndedIterator`]s.
|
|
///
|
|
/// [`DoubleEndedIterator`]: trait.DoubleEndedIterator.html
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// ```
|
|
/// let a = [1, 2, 3];
|
|
///
|
|
/// let mut iter = a.iter().rev();
|
|
///
|
|
/// assert_eq!(iter.next(), Some(&3));
|
|
/// assert_eq!(iter.next(), Some(&2));
|
|
/// assert_eq!(iter.next(), Some(&1));
|
|
///
|
|
/// assert_eq!(iter.next(), None);
|
|
/// ```
|
|
#[inline]
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
fn rev(self) -> Rev<Self> where Self: Sized + DoubleEndedIterator {
|
|
Rev{iter: self}
|
|
}
|
|
|
|
/// Converts an iterator of pairs into a pair of containers.
|
|
///
|
|
/// `unzip()` consumes an entire iterator of pairs, producing two
|
|
/// collections: one from the left elements of the pairs, and one
|
|
/// from the right elements.
|
|
///
|
|
/// This function is, in some sense, the opposite of [`zip()`].
|
|
///
|
|
/// [`zip()`]: #method.zip
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// Basic usage:
|
|
///
|
|
/// ```
|
|
/// 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)>,
|
|
{
|
|
let mut ts: FromA = Default::default();
|
|
let mut us: FromB = Default::default();
|
|
|
|
for (t, u) in self {
|
|
ts.extend(Some(t));
|
|
us.extend(Some(u));
|
|
}
|
|
|
|
(ts, us)
|
|
}
|
|
|
|
/// Creates an iterator which [`clone()`]s all of its elements.
|
|
///
|
|
/// This is useful when you have an iterator over `&T`, but you need an
|
|
/// iterator over `T`.
|
|
///
|
|
/// [`clone()`]: ../../std/clone/trait.Clone.html#tymethod.clone
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// Basic usage:
|
|
///
|
|
/// ```
|
|
/// let a = [1, 2, 3];
|
|
///
|
|
/// let v_cloned: Vec<_> = a.iter().cloned().collect();
|
|
///
|
|
/// // cloned is the same as .map(|&x| x), for integers
|
|
/// let v_map: Vec<_> = a.iter().map(|&x| x).collect();
|
|
///
|
|
/// assert_eq!(v_cloned, vec![1, 2, 3]);
|
|
/// assert_eq!(v_map, vec![1, 2, 3]);
|
|
/// ```
|
|
#[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.
|
|
///
|
|
/// Instead of stopping at [`None`], the iterator will instead start again,
|
|
/// from the beginning. After iterating again, it will start at the
|
|
/// beginning again. And again. And again. Forever.
|
|
///
|
|
/// [`None`]: ../../std/option/enum.Option.html#variant.None
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// Basic usage:
|
|
///
|
|
/// ```
|
|
/// let a = [1, 2, 3];
|
|
///
|
|
/// let mut it = a.iter().cycle();
|
|
///
|
|
/// assert_eq!(it.next(), Some(&1));
|
|
/// assert_eq!(it.next(), Some(&2));
|
|
/// assert_eq!(it.next(), Some(&3));
|
|
/// assert_eq!(it.next(), Some(&1));
|
|
/// assert_eq!(it.next(), Some(&2));
|
|
/// assert_eq!(it.next(), Some(&3));
|
|
/// assert_eq!(it.next(), Some(&1));
|
|
/// ```
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
#[inline]
|
|
fn cycle(self) -> Cycle<Self> where Self: Sized + Clone {
|
|
Cycle{orig: self.clone(), iter: self}
|
|
}
|
|
|
|
/// Sums the elements of an iterator.
|
|
///
|
|
/// Takes each element, adds them together, and returns the result.
|
|
///
|
|
/// An empty iterator returns the zero value of the type.
|
|
///
|
|
/// # Panics
|
|
///
|
|
/// When calling `sum()` and a primitive integer type is being returned, this
|
|
/// method will panic if the computation overflows and debug assertions are
|
|
/// enabled.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// Basic usage:
|
|
///
|
|
/// ```
|
|
/// let a = [1, 2, 3];
|
|
/// let sum: i32 = a.iter().sum();
|
|
///
|
|
/// assert_eq!(sum, 6);
|
|
/// ```
|
|
#[stable(feature = "iter_arith", since = "1.11.0")]
|
|
fn sum<S>(self) -> S
|
|
where Self: Sized,
|
|
S: Sum<Self::Item>,
|
|
{
|
|
Sum::sum(self)
|
|
}
|
|
|
|
/// Iterates over the entire iterator, multiplying all the elements
|
|
///
|
|
/// An empty iterator returns the one value of the type.
|
|
///
|
|
/// # Panics
|
|
///
|
|
/// When calling `product()` and a primitive integer type is being returned,
|
|
/// method will panic if the computation overflows and debug assertions are
|
|
/// enabled.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// ```
|
|
/// fn factorial(n: u32) -> u32 {
|
|
/// (1..).take_while(|&i| i <= n).product()
|
|
/// }
|
|
/// assert_eq!(factorial(0), 1);
|
|
/// assert_eq!(factorial(1), 1);
|
|
/// assert_eq!(factorial(5), 120);
|
|
/// ```
|
|
#[stable(feature = "iter_arith", since = "1.11.0")]
|
|
fn product<P>(self) -> P
|
|
where Self: Sized,
|
|
P: Product<Self::Item>,
|
|
{
|
|
Product::product(self)
|
|
}
|
|
|
|
/// Lexicographically compares the elements of this `Iterator` with those
|
|
/// of another.
|
|
#[stable(feature = "iter_order", since = "1.5.0")]
|
|
fn cmp<I>(mut self, other: I) -> Ordering where
|
|
I: IntoIterator<Item = Self::Item>,
|
|
Self::Item: Ord,
|
|
Self: Sized,
|
|
{
|
|
let mut other = other.into_iter();
|
|
|
|
loop {
|
|
match (self.next(), other.next()) {
|
|
(None, None) => return Ordering::Equal,
|
|
(None, _ ) => return Ordering::Less,
|
|
(_ , None) => return Ordering::Greater,
|
|
(Some(x), Some(y)) => match x.cmp(&y) {
|
|
Ordering::Equal => (),
|
|
non_eq => return non_eq,
|
|
},
|
|
}
|
|
}
|
|
}
|
|
|
|
/// Lexicographically compares the elements of this `Iterator` with those
|
|
/// of another.
|
|
#[stable(feature = "iter_order", since = "1.5.0")]
|
|
fn partial_cmp<I>(mut self, other: I) -> Option<Ordering> where
|
|
I: IntoIterator,
|
|
Self::Item: PartialOrd<I::Item>,
|
|
Self: Sized,
|
|
{
|
|
let mut other = other.into_iter();
|
|
|
|
loop {
|
|
match (self.next(), other.next()) {
|
|
(None, None) => return Some(Ordering::Equal),
|
|
(None, _ ) => return Some(Ordering::Less),
|
|
(_ , None) => return Some(Ordering::Greater),
|
|
(Some(x), Some(y)) => match x.partial_cmp(&y) {
|
|
Some(Ordering::Equal) => (),
|
|
non_eq => return non_eq,
|
|
},
|
|
}
|
|
}
|
|
}
|
|
|
|
/// Determines if the elements of this `Iterator` are equal to those of
|
|
/// another.
|
|
#[stable(feature = "iter_order", since = "1.5.0")]
|
|
fn eq<I>(mut self, other: I) -> bool where
|
|
I: IntoIterator,
|
|
Self::Item: PartialEq<I::Item>,
|
|
Self: Sized,
|
|
{
|
|
let mut other = other.into_iter();
|
|
|
|
loop {
|
|
match (self.next(), other.next()) {
|
|
(None, None) => return true,
|
|
(None, _) | (_, None) => return false,
|
|
(Some(x), Some(y)) => if x != y { return false },
|
|
}
|
|
}
|
|
}
|
|
|
|
/// Determines if the elements of this `Iterator` are unequal to those of
|
|
/// another.
|
|
#[stable(feature = "iter_order", since = "1.5.0")]
|
|
fn ne<I>(mut self, other: I) -> bool where
|
|
I: IntoIterator,
|
|
Self::Item: PartialEq<I::Item>,
|
|
Self: Sized,
|
|
{
|
|
let mut other = other.into_iter();
|
|
|
|
loop {
|
|
match (self.next(), other.next()) {
|
|
(None, None) => return false,
|
|
(None, _) | (_, None) => return true,
|
|
(Some(x), Some(y)) => if x.ne(&y) { return true },
|
|
}
|
|
}
|
|
}
|
|
|
|
/// Determines if the elements of this `Iterator` are lexicographically
|
|
/// less than those of another.
|
|
#[stable(feature = "iter_order", since = "1.5.0")]
|
|
fn lt<I>(mut self, other: I) -> bool where
|
|
I: IntoIterator,
|
|
Self::Item: PartialOrd<I::Item>,
|
|
Self: Sized,
|
|
{
|
|
let mut other = other.into_iter();
|
|
|
|
loop {
|
|
match (self.next(), other.next()) {
|
|
(None, None) => return false,
|
|
(None, _ ) => return true,
|
|
(_ , None) => return false,
|
|
(Some(x), Some(y)) => {
|
|
match x.partial_cmp(&y) {
|
|
Some(Ordering::Less) => return true,
|
|
Some(Ordering::Equal) => {}
|
|
Some(Ordering::Greater) => return false,
|
|
None => return false,
|
|
}
|
|
},
|
|
}
|
|
}
|
|
}
|
|
|
|
/// Determines if the elements of this `Iterator` are lexicographically
|
|
/// less or equal to those of another.
|
|
#[stable(feature = "iter_order", since = "1.5.0")]
|
|
fn le<I>(mut self, other: I) -> bool where
|
|
I: IntoIterator,
|
|
Self::Item: PartialOrd<I::Item>,
|
|
Self: Sized,
|
|
{
|
|
let mut other = other.into_iter();
|
|
|
|
loop {
|
|
match (self.next(), other.next()) {
|
|
(None, None) => return true,
|
|
(None, _ ) => return true,
|
|
(_ , None) => return false,
|
|
(Some(x), Some(y)) => {
|
|
match x.partial_cmp(&y) {
|
|
Some(Ordering::Less) => return true,
|
|
Some(Ordering::Equal) => {}
|
|
Some(Ordering::Greater) => return false,
|
|
None => return false,
|
|
}
|
|
},
|
|
}
|
|
}
|
|
}
|
|
|
|
/// Determines if the elements of this `Iterator` are lexicographically
|
|
/// greater than those of another.
|
|
#[stable(feature = "iter_order", since = "1.5.0")]
|
|
fn gt<I>(mut self, other: I) -> bool where
|
|
I: IntoIterator,
|
|
Self::Item: PartialOrd<I::Item>,
|
|
Self: Sized,
|
|
{
|
|
let mut other = other.into_iter();
|
|
|
|
loop {
|
|
match (self.next(), other.next()) {
|
|
(None, None) => return false,
|
|
(None, _ ) => return false,
|
|
(_ , None) => return true,
|
|
(Some(x), Some(y)) => {
|
|
match x.partial_cmp(&y) {
|
|
Some(Ordering::Less) => return false,
|
|
Some(Ordering::Equal) => {}
|
|
Some(Ordering::Greater) => return true,
|
|
None => return false,
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
/// Determines if the elements of this `Iterator` are lexicographically
|
|
/// greater than or equal to those of another.
|
|
#[stable(feature = "iter_order", since = "1.5.0")]
|
|
fn ge<I>(mut self, other: I) -> bool where
|
|
I: IntoIterator,
|
|
Self::Item: PartialOrd<I::Item>,
|
|
Self: Sized,
|
|
{
|
|
let mut other = other.into_iter();
|
|
|
|
loop {
|
|
match (self.next(), other.next()) {
|
|
(None, None) => return true,
|
|
(None, _ ) => return false,
|
|
(_ , None) => return true,
|
|
(Some(x), Some(y)) => {
|
|
match x.partial_cmp(&y) {
|
|
Some(Ordering::Less) => return false,
|
|
Some(Ordering::Equal) => {}
|
|
Some(Ordering::Greater) => return true,
|
|
None => return false,
|
|
}
|
|
},
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
/// Select an element from an iterator based on the given projection
|
|
/// and "comparison" function.
|
|
///
|
|
/// This is an idiosyncratic helper to try to factor out the
|
|
/// commonalities of {max,min}{,_by}. In particular, this avoids
|
|
/// having to implement optimizations several times.
|
|
#[inline]
|
|
fn select_fold1<I,B, FProj, FCmp>(mut it: I,
|
|
mut f_proj: FProj,
|
|
mut f_cmp: FCmp) -> Option<(B, I::Item)>
|
|
where I: Iterator,
|
|
FProj: FnMut(&I::Item) -> B,
|
|
FCmp: FnMut(&B, &I::Item, &B, &I::Item) -> bool
|
|
{
|
|
// start with the first element as our selection. This avoids
|
|
// having to use `Option`s inside the loop, translating to a
|
|
// sizeable performance gain (6x in one case).
|
|
it.next().map(|mut sel| {
|
|
let mut sel_p = f_proj(&sel);
|
|
|
|
for x in it {
|
|
let x_p = f_proj(&x);
|
|
if f_cmp(&sel_p, &sel, &x_p, &x) {
|
|
sel = x;
|
|
sel_p = x_p;
|
|
}
|
|
}
|
|
(sel_p, sel)
|
|
})
|
|
}
|
|
|
|
#[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() }
|
|
fn nth(&mut self, n: usize) -> Option<Self::Item> {
|
|
(**self).nth(n)
|
|
}
|
|
}
|