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authorpravic <[email protected]>2016-04-29 21:16:15 +0300
committerpravic <[email protected]>2016-04-29 21:16:15 +0300
commit77e9a3167b4aaadf3583a0c1d1ee0d9e63c9a000 (patch)
tree710e445d56a1a582b8eff19b7b4b180276eae122 /libcore/iter
parenttweak: /driver option specifies /fixed:no implicitly as well (diff)
downloadkmd-env-rs-77e9a3167b4aaadf3583a0c1d1ee0d9e63c9a000.tar.xz
kmd-env-rs-77e9a3167b4aaadf3583a0c1d1ee0d9e63c9a000.zip
update libcore to 2016-04-29 nightly
Diffstat (limited to 'libcore/iter')
-rw-r--r--libcore/iter/iterator.rs2111
-rw-r--r--libcore/iter/mod.rs1657
-rw-r--r--libcore/iter/range.rs548
-rw-r--r--libcore/iter/sources.rs270
-rw-r--r--libcore/iter/traits.rs526
5 files changed, 5112 insertions, 0 deletions
diff --git a/libcore/iter/iterator.rs b/libcore/iter/iterator.rs
new file mode 100644
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--- /dev/null
+++ b/libcore/iter/iterator.rs
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+// Copyright 2013-2016 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.
+
+use clone::Clone;
+use cmp::{Ord, PartialOrd, PartialEq, Ordering};
+use default::Default;
+use marker;
+use num::{Zero, One};
+use ops::{Add, FnMut, Mul};
+use option::Option::{self, Some, None};
+use marker::Sized;
+
+use super::{Chain, Cycle, Cloned, Enumerate, Filter, FilterMap, FlatMap, Fuse,
+ Inspect, Map, Peekable, Scan, Skip, SkipWhile, Take, TakeWhile, Rev,
+ Zip};
+use super::ChainState;
+use super::{DoubleEndedIterator, ExactSizeIterator, Extend, FromIterator,
+ IntoIterator};
+
+fn _assert_is_object_safe(_: &Iterator<Item=()>) {}
+
+/// An interface for dealing with iterators.
+///
+/// This is the main iterator trait. For more about the concept of iterators
+/// generally, please see the [module-level documentation]. In particular, you
+/// may want to know how to [implement `Iterator`][impl].
+///
+/// [module-level documentation]: index.html
+/// [impl]: index.html#implementing-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 over.
+ #[stable(feature = "rust1", since = "1.0.0")]
+ type Item;
+
+ /// Advances the iterator and returns the next value.
+ ///
+ /// Returns `None` when iteration is finished. Individual iterator
+ /// implementations may choose to resume iteration, and so calling `next()`
+ /// again may or may not eventually start returning `Some(Item)` again at some
+ /// point.
+ ///
+ /// # Examples
+ ///
+ /// Basic usage:
+ ///
+ /// ```
+ /// let a = [1, 2, 3];
+ ///
+ /// let mut iter = a.iter();
+ ///
+ /// // A call to next() returns the next value...
+ /// assert_eq!(Some(&1), iter.next());
+ /// assert_eq!(Some(&2), iter.next());
+ /// assert_eq!(Some(&3), iter.next());
+ ///
+ /// // ... and then None once it's over.
+ /// assert_eq!(None, iter.next());
+ ///
+ /// // More calls may or may not return None. Here, they always will.
+ /// assert_eq!(None, iter.next());
+ /// assert_eq!(None, iter.next());
+ /// ```
+ #[stable(feature = "rust1", since = "1.0.0")]
+ fn next(&mut self) -> Option<Self::Item>;
+
+ /// Returns the bounds on the remaining length of the iterator.
+ ///
+ /// Specifically, `size_hint()` returns a tuple where the first element
+ /// is the lower bound, and the second element is the upper bound.
+ ///
+ /// The second half of the tuple that is returned is an `Option<usize>`. A
+ /// `None` here means that either there is no known upper bound, or the
+ /// upper bound is larger than `usize`.
+ ///
+ /// # Implementation notes
+ ///
+ /// It is not enforced that an iterator implementation yields the declared
+ /// number of elements. A buggy iterator may yield less than the lower bound
+ /// or more than the upper bound of elements.
+ ///
+ /// `size_hint()` is primarily intended to be used for optimizations such as
+ /// reserving space for the elements of the iterator, but must not be
+ /// trusted to e.g. omit bounds checks in unsafe code. An incorrect
+ /// implementation of `size_hint()` should not lead to memory safety
+ /// violations.
+ ///
+ /// That said, the implementation should provide a correct estimation,
+ /// because otherwise it would be a violation of the trait's protocol.
+ ///
+ /// The default implementation returns `(0, None)` which is correct for any
+ /// iterator.
+ ///
+ /// # Examples
+ ///
+ /// Basic usage:
+ ///
+ /// ```
+ /// let a = [1, 2, 3];
+ /// let iter = a.iter();
+ ///
+ /// assert_eq!((3, Some(3)), iter.size_hint());
+ /// ```
+ ///
+ /// A more complex example:
+ ///
+ /// ```
+ /// // The even numbers from zero to ten.
+ /// let iter = (0..10).filter(|x| x % 2 == 0);
+ ///
+ /// // We might iterate from zero to ten times. Knowing that it's five
+ /// // exactly wouldn't be possible without executing filter().
+ /// assert_eq!((0, Some(10)), iter.size_hint());
+ ///
+ /// // Let's add one five more numbers with chain()
+ /// let iter = (0..10).filter(|x| x % 2 == 0).chain(15..20);
+ ///
+ /// // now both bounds are increased by five
+ /// assert_eq!((5, Some(15)), iter.size_hint());
+ /// ```
+ ///
+ /// Returning `None` for an upper bound:
+ ///
+ /// ```
+ /// // an infinite iterator has no upper bound
+ /// let iter = 0..;
+ ///
+ /// assert_eq!((0, None), iter.size_hint());
+ /// ```
+ #[inline]
+ #[stable(feature = "rust1", since = "1.0.0")]
+ fn size_hint(&self) -> (usize, Option<usize>) { (0, None) }
+
+ /// Consumes the iterator, counting the number of iterations and returning it.
+ ///
+ /// This method will evaluate the iterator until its [`next()`] returns
+ /// `None`. Once `None` is encountered, `count()` returns the number of
+ /// times it called [`next()`].
+ ///
+ /// [`next()`]: #tymethod.next
+ ///
+ /// # Overflow Behavior
+ ///
+ /// The method does no guarding against overflows, so counting elements of
+ /// an iterator with more than `usize::MAX` elements 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`
+ /// elements.
+ ///
+ /// # Examples
+ ///
+ /// Basic usage:
+ ///
+ /// ```
+ /// let a = [1, 2, 3];
+ /// assert_eq!(a.iter().count(), 3);
+ ///
+ /// 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 {
+ // Might overflow.
+ self.fold(0, |cnt, _| cnt + 1)
+ }
+
+ /// Consumes the iterator, returning the last element.
+ ///
+ /// This method will evaluate the iterator until it returns `None`. While
+ /// doing so, it keeps track of the current element. After `None` is
+ /// returned, `last()` will then return the last element it saw.
+ ///
+ /// # Examples
+ ///
+ /// Basic usage:
+ ///
+ /// ```
+ /// let a = [1, 2, 3];
+ /// assert_eq!(a.iter().last(), Some(&3));
+ ///
+ /// let a = [1, 2, 3, 4, 5];
+ /// assert_eq!(a.iter().last(), Some(&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
+ }
+
+ /// Consumes the `n` first elements of the iterator, then returns the
+ /// `next()` one.
+ ///
+ /// This method will evaluate the iterator `n` times, discarding those elements.
+ /// After it does so, it will call [`next()`] and return its value.
+ ///
+ /// [`next()`]: #tymethod.next
+ ///
+ /// Like most indexing operations, the count starts from zero, so `nth(0)`
+ /// returns the first value, `nth(1)` the second, and so on.
+ ///
+ /// `nth()` will return `None` if `n` is larger than the length of the
+ /// iterator.
+ ///
+ /// # Examples
+ ///
+ /// Basic usage:
+ ///
+ /// ```
+ /// let a = [1, 2, 3];
+ /// assert_eq!(a.iter().nth(1), Some(&2));
+ /// ```
+ ///
+ /// Calling `nth()` multiple times doesn't rewind the iterator:
+ ///
+ /// ```
+ /// let a = [1, 2, 3];
+ ///
+ /// let mut iter = a.iter();
+ ///
+ /// assert_eq!(iter.nth(1), Some(&2));
+ /// assert_eq!(iter.nth(1), None);
+ /// ```
+ ///
+ /// Returning `None` if there are less than `n` elements:
+ ///
+ /// ```
+ /// let a = [1, 2, 3];
+ /// assert_eq!(a.iter().nth(10), 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 {
+ if n == 0 { return Some(x) }
+ n -= 1;
+ }
+ None
+ }
+
+ /// Takes two iterators and creates a new iterator over both in sequence.
+ ///
+ /// `chain()` will return a new iterator which will first iterate over
+ /// values from the first iterator and then over values from the second
+ /// iterator.
+ ///
+ /// In other words, it links two iterators together, in a chain. 🔗
+ ///
+ /// # Examples
+ ///
+ /// Basic usage:
+ ///
+ /// ```
+ /// let a1 = [1, 2, 3];
+ /// let a2 = [4, 5, 6];
+ ///
+ /// let mut iter = a1.iter().chain(a2.iter());
+ ///
+ /// assert_eq!(iter.next(), Some(&1));
+ /// assert_eq!(iter.next(), Some(&2));
+ /// assert_eq!(iter.next(), Some(&3));
+ /// assert_eq!(iter.next(), Some(&4));
+ /// assert_eq!(iter.next(), Some(&5));
+ /// assert_eq!(iter.next(), Some(&6));
+ /// assert_eq!(iter.next(), None);
+ /// ```
+ ///
+ /// Since the argument to `chain()` uses [`IntoIterator`], we can pass
+ /// anything that can be converted into an [`Iterator`], not just an
+ /// [`Iterator`] itself. For example, slices (`&[T]`) implement
+ /// [`IntoIterator`], and so can be passed to `chain()` directly:
+ ///
+ /// [`IntoIterator`]: trait.IntoIterator.html
+ /// [`Iterator`]: trait.Iterator.html
+ ///
+ /// ```
+ /// let s1 = &[1, 2, 3];
+ /// let s2 = &[4, 5, 6];
+ ///
+ /// let mut iter = s1.iter().chain(s2);
+ ///
+ /// assert_eq!(iter.next(), Some(&1));
+ /// assert_eq!(iter.next(), Some(&2));
+ /// assert_eq!(iter.next(), Some(&3));
+ /// assert_eq!(iter.next(), Some(&4));
+ /// assert_eq!(iter.next(), Some(&5));
+ /// assert_eq!(iter.next(), Some(&6));
+ /// assert_eq!(iter.next(), None);
+ /// ```
+ #[inline]
+ #[stable(feature = "rust1", since = "1.0.0")]
+ fn chain<U>(self, other: U) -> Chain<Self, U::IntoIter> where
+ Self: Sized, U: IntoIterator<Item=Self::Item>,
+ {
+ Chain{a: self, b: other.into_iter(), state: ChainState::Both}
+ }
+
+ /// 'Zips up' two iterators into a single iterator of pairs.
+ ///
+ /// `zip()` returns a new iterator that will iterate over two other
+ /// iterators, returning a tuple where the first element comes from the
+ /// first iterator, and the second element comes from the second iterator.
+ ///
+ /// In other words, it zips two iterators together, into a single one.
+ ///
+ /// When either iterator returns `None`, all further calls to `next()`
+ /// will return `None`.
+ ///
+ /// # Examples
+ ///
+ /// Basic usage:
+ ///
+ /// ```
+ /// let a1 = [1, 2, 3];
+ /// let a2 = [4, 5, 6];
+ ///
+ /// let mut iter = a1.iter().zip(a2.iter());
+ ///
+ /// assert_eq!(iter.next(), Some((&1, &4)));
+ /// assert_eq!(iter.next(), Some((&2, &5)));
+ /// assert_eq!(iter.next(), Some((&3, &6)));
+ /// assert_eq!(iter.next(), None);
+ /// ```
+ ///
+ /// Since the argument to `zip()` uses [`IntoIterator`], we can pass
+ /// anything that can be converted into an [`Iterator`], not just an
+ /// [`Iterator`] itself. For example, slices (`&[T]`) implement
+ /// [`IntoIterator`], and so can be passed to `zip()` directly:
+ ///
+ /// [`IntoIterator`]: trait.IntoIterator.html
+ /// [`Iterator`]: trait.Iterator.html
+ ///
+ /// ```
+ /// let s1 = &[1, 2, 3];
+ /// let s2 = &[4, 5, 6];
+ ///
+ /// let mut iter = s1.iter().zip(s2);
+ ///
+ /// assert_eq!(iter.next(), Some((&1, &4)));
+ /// assert_eq!(iter.next(), Some((&2, &5)));
+ /// assert_eq!(iter.next(), Some((&3, &6)));
+ /// assert_eq!(iter.next(), None);
+ /// ```
+ ///
+ /// `zip()` is often used to zip an infinite iterator to a finite one.
+ /// This works because the finite iterator will eventually return `None`,
+ /// ending the zipper. Zipping with `(0..)` can look a lot like [`enumerate()`]:
+ ///
+ /// ```
+ /// let enumerate: Vec<_> = "foo".chars().enumerate().collect();
+ ///
+ /// let zipper: Vec<_> = (0..).zip("foo".chars()).collect();
+ ///
+ /// assert_eq!((0, 'f'), enumerate[0]);
+ /// assert_eq!((0, 'f'), zipper[0]);
+ ///
+ /// assert_eq!((1, 'o'), enumerate[1]);
+ /// assert_eq!((1, 'o'), zipper[1]);
+ ///
+ /// assert_eq!((2, 'o'), enumerate[2]);
+ /// assert_eq!((2, 'o'), zipper[2]);
+ /// ```
+ ///
+ /// [`enumerate()`]: trait.Iterator.html#method.enumerate
+ #[inline]
+ #[stable(feature = "rust1", since = "1.0.0")]
+ fn zip<U>(self, other: U) -> Zip<Self, U::IntoIter> where
+ Self: Sized, U: IntoIterator
+ {
+ Zip{a: self, b: other.into_iter()}
+ }
+
+ /// Takes a closure and creates an iterator which calls that closure on each
+ /// element.
+ ///
+ /// `map()` transforms one iterator into another, by means of its argument:
+ /// something that implements `FnMut`. It produces a new iterator which
+ /// calls this closure on each element of the original iterator.
+ ///
+ /// If you are good at thinking in types, you can think of `map()` like this:
+ /// If you have an iterator that gives you elements of some type `A`, and
+ /// you want an iterator of some other type `B`, you can use `map()`,
+ /// passing a closure that takes an `A` and returns a `B`.
+ ///
+ /// `map()` is conceptually similar to a [`for`] loop. However, as `map()` is
+ /// lazy, it is best used when you're already working with other iterators.
+ /// If you're doing some sort of looping for a side effect, it's considered
+ /// more idiomatic to use [`for`] than `map()`.
+ ///
+ /// [`for`]: ../../book/loops.html#for
+ ///
+ /// # Examples
+ ///
+ /// Basic usage:
+ ///
+ /// ```
+ /// let a = [1, 2, 3];
+ ///
+ /// let mut iter = a.into_iter().map(|x| 2 * x);
+ ///
+ /// assert_eq!(iter.next(), Some(2));
+ /// assert_eq!(iter.next(), Some(4));
+ /// assert_eq!(iter.next(), Some(6));
+ /// assert_eq!(iter.next(), None);
+ /// ```
+ ///
+ /// If you're doing some sort of side effect, prefer [`for`] to `map()`:
+ ///
+ /// ```
+ /// # #![allow(unused_must_use)]
+ /// // don't do this:
+ /// (0..5).map(|x| println!("{}", x));
+ ///
+ /// // it won't even execute, as it is lazy. Rust will warn you about this.
+ ///
+ /// // Instead, use for:
+ /// for x in 0..5 {
+ /// println!("{}", x);
+ /// }
+ /// ```
+ #[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 which uses a closure to determine if an element
+ /// should be yielded.
+ ///
+ /// The closure must return `true` or `false`. `filter()` creates an
+ /// iterator which calls this closure on each element. If the closure
+ /// returns `true`, then the element is returned. If the closure returns
+ /// `false`, it will try again, and call the closure on the next element,
+ /// seeing if it passes the test.
+ ///
+ /// # Examples
+ ///
+ /// Basic usage:
+ ///
+ /// ```
+ /// let a = [0i32, 1, 2];
+ ///
+ /// let mut iter = a.into_iter().filter(|x| x.is_positive());
+ ///
+ /// assert_eq!(iter.next(), Some(&1));
+ /// assert_eq!(iter.next(), Some(&2));
+ /// assert_eq!(iter.next(), None);
+ /// ```
+ ///
+ /// Because the closure passed to `filter()` 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 = [0, 1, 2];
+ ///
+ /// let mut iter = a.into_iter().filter(|x| **x > 1); // need two *s!
+ ///
+ /// 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)`, 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`.
+ ///
+ /// [`Option<T>`]: ../../std/option/enum.Option.html
+ ///
+ /// 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)`, 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.
+ #[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.
+ ///
+ /// [`usize`]: ../../std/primitive.usize.html
+ /// [`zip()`]: #method.zip
+ ///
+ /// # 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.
+ ///
+ /// [`usize::MAX`]: ../../std/usize/constant.MAX.html
+ ///
+ /// # Panics
+ ///
+ /// The returned iterator might panic if the to-be-returned index would
+ /// overflow a `usize`.
+ ///
+ /// # 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
+ ///
+ /// # 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.
+ ///
+ /// [`map()`]: #method.map
+ ///
+ /// 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.
+ ///
+ /// # 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.
+ ///
+ /// # 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>`] can
+ /// be thought of as single `Result<Collection<T>, E>`. See the examples
+ /// below for more.
+ ///
+ /// [`String`]: ../../std/string/struct.String.html
+ /// [`Result<T, E>`]: ../../std/result/enum.Result.html
+ /// [`char`]: ../../std/primitive.char.html
+ ///
+ /// 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>`]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);
+ /// ```
+ #[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:
+ ///
+ /// ```
+ /// 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`.
+ ///
+ /// # 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.
+ ///
+ /// # 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`.
+ ///
+ /// # 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() {
+ if predicate(v) {
+ return Some(i - 1);
+ }
+ // No need for an overflow check here, because `ExactSizeIterator`
+ // implies that the number of elements fits into a `usize`.
+ i -= 1;
+ }
+ None
+ }
+
+ /// Returns the maximum element of an iterator.
+ ///
+ /// If the two elements are equally maximum, the latest element is
+ /// returned.
+ ///
+ /// # Examples
+ ///
+ /// Basic usage:
+ ///
+ /// ```
+ /// let a = [1, 2, 3];
+ ///
+ /// assert_eq!(a.iter().max(), Some(&3));
+ /// ```
+ #[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 the two elements are equally minimum, the first element is
+ /// returned.
+ ///
+ /// # Examples
+ ///
+ /// Basic usage:
+ ///
+ /// ```
+ /// let a = [1, 2, 3];
+ ///
+ /// assert_eq!(a.iter().min(), Some(&1));
+ /// ```
+ #[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.
+ ///
+ /// Returns the rightmost element if the comparison determines two elements
+ /// to be equally maximum.
+ ///
+ /// # 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 minimum value from the
+ /// specified function.
+ ///
+ /// Returns the latest element if the comparison determines two elements
+ /// to be equally minimum.
+ ///
+ /// # 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)
+ }
+
+ /// 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)>,
+ {
+ 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));
+ 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`.
+ ///
+ /// # 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.
+ ///
+ /// # 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.
+ ///
+ /// # Examples
+ ///
+ /// Basic usage:
+ ///
+ /// ```
+ /// #![feature(iter_arith)]
+ ///
+ /// let a = [1, 2, 3];
+ /// let sum: i32 = a.iter().sum();
+ ///
+ /// assert_eq!(sum, 6);
+ /// ```
+ #[unstable(feature = "iter_arith", reason = "bounds recently changed",
+ issue = "27739")]
+ fn sum<S>(self) -> S where
+ S: Add<Self::Item, Output=S> + Zero,
+ Self: Sized,
+ {
+ self.fold(Zero::zero(), |s, e| s + e)
+ }
+
+ /// Iterates over the entire iterator, multiplying all the elements
+ ///
+ /// An empty iterator returns the one value of the type.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// #![feature(iter_arith)]
+ ///
+ /// 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);
+ /// ```
+ #[unstable(feature="iter_arith", reason = "bounds recently changed",
+ issue = "27739")]
+ fn product<P>(self) -> P where
+ P: Mul<Self::Item, Output=P> + One,
+ Self: Sized,
+ {
+ self.fold(One::one(), |p, e| p * e)
+ }
+
+ /// 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() }
+}
diff --git a/libcore/iter/mod.rs b/libcore/iter/mod.rs
new file mode 100644
index 0000000..abc199c
--- /dev/null
+++ b/libcore/iter/mod.rs
@@ -0,0 +1,1657 @@
+// Copyright 2013-2016 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 iteration.
+//!
+//! If you've found yourself with a collection of some kind, and needed to
+//! perform an operation on the elements of said collection, you'll quickly run
+//! into 'iterators'. Iterators are heavily used in idiomatic Rust code, so
+//! it's worth becoming familiar with them.
+//!
+//! Before explaining more, let's talk about how this module is structured:
+//!
+//! # Organization
+//!
+//! This module is largely organized by type:
+//!
+//! * [Traits] are the core portion: these traits define what kind of iterators
+//! exist and what you can do with them. The methods of these traits are worth
+//! putting some extra study time into.
+//! * [Functions] provide some helpful ways to create some basic iterators.
+//! * [Structs] are often the return types of the various methods on this
+//! module's traits. You'll usually want to look at the method that creates
+//! the `struct`, rather than the `struct` itself. For more detail about why,
+//! see '[Implementing Iterator](#implementing-iterator)'.
+//!
+//! [Traits]: #traits
+//! [Functions]: #functions
+//! [Structs]: #structs
+//!
+//! That's it! Let's dig into iterators.
+//!
+//! # Iterator
+//!
+//! The heart and soul of this module is the [`Iterator`] trait. The core of
+//! [`Iterator`] looks like this:
+//!
+//! ```
+//! trait Iterator {
+//! type Item;
+//! fn next(&mut self) -> Option<Self::Item>;
+//! }
+//! ```
+//!
+//! An iterator has a method, [`next()`], which when called, returns an
+//! [`Option`]`<Item>`. [`next()`] will return `Some(Item)` as long as there
+//! are elements, and once they've all been exhausted, will return `None` to
+//! indicate that iteration is finished. Individual iterators may choose to
+//! resume iteration, and so calling [`next()`] again may or may not eventually
+//! start returning `Some(Item)` again at some point.
+//!
+//! [`Iterator`]'s full definition includes a number of other methods as well,
+//! but they are default methods, built on top of [`next()`], and so you get
+//! them for free.
+//!
+//! Iterators are also composable, and it's common to chain them together to do
+//! more complex forms of processing. See the [Adapters](#adapters) section
+//! below for more details.
+//!
+//! [`Iterator`]: trait.Iterator.html
+//! [`next()`]: trait.Iterator.html#tymethod.next
+//! [`Option`]: ../../std/option/enum.Option.html
+//!
+//! # The three forms of iteration
+//!
+//! There are three common methods which can create iterators from a collection:
+//!
+//! * `iter()`, which iterates over `&T`.
+//! * `iter_mut()`, which iterates over `&mut T`.
+//! * `into_iter()`, which iterates over `T`.
+//!
+//! Various things in the standard library may implement one or more of the
+//! three, where appropriate.
+//!
+//! # Implementing Iterator
+//!
+//! Creating an iterator of your own involves two steps: creating a `struct` to
+//! hold the iterator's state, and then `impl`ementing [`Iterator`] for that
+//! `struct`. This is why there are so many `struct`s in this module: there is
+//! one for each iterator and iterator adapter.
+//!
+//! Let's make an iterator named `Counter` which counts from `1` to `5`:
+//!
+//! ```
+//! // First, the struct:
+//!
+//! /// An iterator which counts from one to five
+//! struct Counter {
+//! count: usize,
+//! }
+//!
+//! // we want our count to start at one, so let's add a new() method to help.
+//! // This isn't strictly necessary, but is convenient. Note that we start
+//! // `count` at zero, we'll see why in `next()`'s implementation below.
+//! impl Counter {
+//! fn new() -> Counter {
+//! Counter { count: 0 }
+//! }
+//! }
+//!
+//! // Then, we implement `Iterator` for our `Counter`:
+//!
+//! impl Iterator for Counter {
+//! // we will be counting with usize
+//! type Item = usize;
+//!
+//! // next() is the only required method
+//! fn next(&mut self) -> Option<usize> {
+//! // increment our count. This is why we started at zero.
+//! self.count += 1;
+//!
+//! // check to see if we've finished counting or not.
+//! if self.count < 6 {
+//! Some(self.count)
+//! } else {
+//! None
+//! }
+//! }
+//! }
+//!
+//! // And now we can use it!
+//!
+//! let mut counter = Counter::new();
+//!
+//! let x = counter.next().unwrap();
+//! println!("{}", x);
+//!
+//! let x = counter.next().unwrap();
+//! println!("{}", x);
+//!
+//! let x = counter.next().unwrap();
+//! println!("{}", x);
+//!
+//! let x = counter.next().unwrap();
+//! println!("{}", x);
+//!
+//! let x = counter.next().unwrap();
+//! println!("{}", x);
+//! ```
+//!
+//! This will print `1` through `5`, each on their own line.
+//!
+//! Calling `next()` this way gets repetitive. Rust has a construct which can
+//! call `next()` on your iterator, until it reaches `None`. Let's go over that
+//! next.
+//!
+//! # for Loops and IntoIterator
+//!
+//! Rust's `for` loop syntax is actually sugar for iterators. Here's a basic
+//! example of `for`:
+//!
+//! ```
+//! let values = vec![1, 2, 3, 4, 5];
+//!
+//! for x in values {
+//! println!("{}", x);
+//! }
+//! ```
+//!
+//! This will print the numbers one through five, each on their own line. But
+//! you'll notice something here: we never called anything on our vector to
+//! produce an iterator. What gives?
+//!
+//! There's a trait in the standard library for converting something into an
+//! iterator: [`IntoIterator`]. This trait has one method, [`into_iter()`],
+//! which converts the thing implementing [`IntoIterator`] into an iterator.
+//! Let's take a look at that `for` loop again, and what the compiler converts
+//! it into:
+//!
+//! [`IntoIterator`]: trait.IntoIterator.html
+//! [`into_iter()`]: trait.IntoIterator.html#tymethod.into_iter
+//!
+//! ```
+//! let values = vec![1, 2, 3, 4, 5];
+//!
+//! for x in values {
+//! println!("{}", x);
+//! }
+//! ```
+//!
+//! Rust de-sugars this into:
+//!
+//! ```
+//! let values = vec![1, 2, 3, 4, 5];
+//! {
+//! let result = match IntoIterator::into_iter(values) {
+//! mut iter => loop {
+//! match iter.next() {
+//! Some(x) => { println!("{}", x); },
+//! None => break,
+//! }
+//! },
+//! };
+//! result
+//! }
+//! ```
+//!
+//! First, we call `into_iter()` on the value. Then, we match on the iterator
+//! that returns, calling [`next()`] over and over until we see a `None`. At
+//! that point, we `break` out of the loop, and we're done iterating.
+//!
+//! There's one more subtle bit here: the standard library contains an
+//! interesting implementation of [`IntoIterator`]:
+//!
+//! ```ignore
+//! impl<I: Iterator> IntoIterator for I
+//! ```
+//!
+//! In other words, all [`Iterator`]s implement [`IntoIterator`], by just
+//! returning themselves. This means two things:
+//!
+//! 1. If you're writing an [`Iterator`], you can use it with a `for` loop.
+//! 2. If you're creating a collection, implementing [`IntoIterator`] for it
+//! will allow your collection to be used with the `for` loop.
+//!
+//! # Adapters
+//!
+//! Functions which take an [`Iterator`] and return another [`Iterator`] are
+//! often called 'iterator adapters', as they're a form of the 'adapter
+//! pattern'.
+//!
+//! Common iterator adapters include [`map()`], [`take()`], and [`collect()`].
+//! For more, see their documentation.
+//!
+//! [`map()`]: trait.Iterator.html#method.map
+//! [`take()`]: trait.Iterator.html#method.take
+//! [`collect()`]: trait.Iterator.html#method.collect
+//!
+//! # Laziness
+//!
+//! Iterators (and iterator [adapters](#adapters)) are *lazy*. This means that
+//! just creating an iterator doesn't _do_ a whole lot. Nothing really happens
+//! until you call [`next()`]. This is sometimes a source of confusion when
+//! creating an iterator solely for its side effects. For example, the [`map()`]
+//! method calls a closure on each element it iterates over:
+//!
+//! ```
+//! # #![allow(unused_must_use)]
+//! let v = vec![1, 2, 3, 4, 5];
+//! v.iter().map(|x| println!("{}", x));
+//! ```
+//!
+//! This will not print any values, as we only created an iterator, rather than
+//! using it. The compiler will warn us about this kind of behavior:
+//!
+//! ```text
+//! warning: unused result which must be used: iterator adaptors are lazy and
+//! do nothing unless consumed
+//! ```
+//!
+//! The idiomatic way to write a [`map()`] for its side effects is to use a
+//! `for` loop instead:
+//!
+//! ```
+//! let v = vec![1, 2, 3, 4, 5];
+//!
+//! for x in &v {
+//! println!("{}", x);
+//! }
+//! ```
+//!
+//! [`map()`]: trait.Iterator.html#method.map
+//!
+//! The two most common ways to evaluate an iterator are to use a `for` loop
+//! like this, or using the [`collect()`] adapter to produce a new collection.
+//!
+//! [`collect()`]: trait.Iterator.html#method.collect
+//!
+//! # Infinity
+//!
+//! Iterators do not have to be finite. As an example, an open-ended range is
+//! an infinite iterator:
+//!
+//! ```
+//! let numbers = 0..;
+//! ```
+//!
+//! It is common to use the [`take()`] iterator adapter to turn an infinite
+//! iterator into a finite one:
+//!
+//! ```
+//! let numbers = 0..;
+//! let five_numbers = numbers.take(5);
+//!
+//! for number in five_numbers {
+//! println!("{}", number);
+//! }
+//! ```
+//!
+//! This will print the numbers `0` through `4`, each on their own line.
+//!
+//! [`take()`]: trait.Iterator.html#method.take
+
+#![stable(feature = "rust1", since = "1.0.0")]
+
+use clone::Clone;
+use cmp;
+use fmt;
+use ops::FnMut;
+use option::Option::{self, Some, None};
+use usize;
+
+#[stable(feature = "rust1", since = "1.0.0")]
+pub use self::iterator::Iterator;
+
+#[unstable(feature = "step_trait",
+ reason = "likely to be replaced by finer-grained traits",
+ issue = "27741")]
+pub use self::range::Step;
+#[unstable(feature = "step_by", reason = "recent addition",
+ issue = "27741")]
+pub use self::range::StepBy;
+
+#[stable(feature = "rust1", since = "1.0.0")]
+pub use self::sources::{Repeat, repeat};
+#[stable(feature = "iter_empty", since = "1.2.0")]
+pub use self::sources::{Empty, empty};
+#[stable(feature = "iter_once", since = "1.2.0")]
+pub use self::sources::{Once, once};
+
+#[stable(feature = "rust1", since = "1.0.0")]
+pub use self::traits::{FromIterator, IntoIterator, DoubleEndedIterator, Extend,
+ ExactSizeIterator};
+
+mod iterator;
+mod range;
+mod sources;
+mod traits;
+
+/// An double-ended iterator with the direction inverted.
+///
+/// This `struct` is created by the [`rev()`] method on [`Iterator`]. See its
+/// documentation for more.
+///
+/// [`rev()`]: trait.Iterator.html#method.rev
+/// [`Iterator`]: trait.Iterator.html
+#[derive(Clone, Debug)]
+#[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() }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<I> ExactSizeIterator for Rev<I>
+ where I: ExactSizeIterator + DoubleEndedIterator {}
+
+/// An iterator that clones the elements of an underlying iterator.
+///
+/// This `struct` is created by the [`cloned()`] method on [`Iterator`]. See its
+/// documentation for more.
+///
+/// [`cloned()`]: trait.Iterator.html#method.cloned
+/// [`Iterator`]: trait.Iterator.html
+#[stable(feature = "iter_cloned", since = "1.1.0")]
+#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
+#[derive(Clone, Debug)]
+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
+{}
+
+/// An iterator that repeats endlessly.
+///
+/// This `struct` is created by the [`cycle()`] method on [`Iterator`]. See its
+/// documentation for more.
+///
+/// [`cycle()`]: trait.Iterator.html#method.cycle
+/// [`Iterator`]: trait.Iterator.html
+#[derive(Clone, Debug)]
+#[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)
+ }
+ }
+}
+
+/// An iterator that strings two iterators together.
+///
+/// This `struct` is created by the [`chain()`] method on [`Iterator`]. See its
+/// documentation for more.
+///
+/// [`chain()`]: trait.Iterator.html#method.chain
+/// [`Iterator`]: trait.Iterator.html
+#[derive(Clone, Debug)]
+#[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,
+ state: ChainState,
+}
+
+// The iterator protocol specifies that iteration ends with the return value
+// `None` from `.next()` (or `.next_back()`) and it is unspecified what
+// further calls return. The chain adaptor must account for this since it uses
+// two subiterators.
+//
+// It uses three states:
+//
+// - Both: `a` and `b` are remaining
+// - Front: `a` remaining
+// - Back: `b` remaining
+//
+// The fourth state (neither iterator is remaining) only occurs after Chain has
+// returned None once, so we don't need to store this state.
+#[derive(Clone, Debug)]
+enum ChainState {
+ // both front and back iterator are remaining
+ Both,
+ // only front is remaining
+ Front,
+ // only back is remaining
+ Back,
+}
+
+#[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> {
+ match self.state {
+ ChainState::Both => match self.a.next() {
+ elt @ Some(..) => elt,
+ None => {
+ self.state = ChainState::Back;
+ self.b.next()
+ }
+ },
+ ChainState::Front => self.a.next(),
+ ChainState::Back => self.b.next(),
+ }
+ }
+
+ #[inline]
+ fn count(self) -> usize {
+ match self.state {
+ ChainState::Both => self.a.count() + self.b.count(),
+ ChainState::Front => self.a.count(),
+ ChainState::Back => self.b.count(),
+ }
+ }
+
+ #[inline]
+ fn nth(&mut self, mut n: usize) -> Option<A::Item> {
+ match self.state {
+ ChainState::Both | ChainState::Front => {
+ for x in self.a.by_ref() {
+ if n == 0 {
+ return Some(x)
+ }
+ n -= 1;
+ }
+ if let ChainState::Both = self.state {
+ self.state = ChainState::Back;
+ }
+ }
+ ChainState::Back => {}
+ }
+ if let ChainState::Back = self.state {
+ self.b.nth(n)
+ } else {
+ None
+ }
+ }
+
+ #[inline]
+ fn last(self) -> Option<A::Item> {
+ match self.state {
+ ChainState::Both => {
+ // Must exhaust a before b.
+ let a_last = self.a.last();
+ let b_last = self.b.last();
+ b_last.or(a_last)
+ },
+ ChainState::Front => self.a.last(),
+ ChainState::Back => self.b.last()
+ }
+ }
+
+ #[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.state {
+ ChainState::Both => match self.b.next_back() {
+ elt @ Some(..) => elt,
+ None => {
+ self.state = ChainState::Front;
+ self.a.next_back()
+ }
+ },
+ ChainState::Front => self.a.next_back(),
+ ChainState::Back => self.b.next_back(),
+ }
+ }
+}
+
+/// An iterator that iterates two other iterators simultaneously.
+///
+/// This `struct` is created by the [`zip()`] method on [`Iterator`]. See its
+/// documentation for more.
+///
+/// [`zip()`]: trait.Iterator.html#method.zip
+/// [`Iterator`]: trait.Iterator.html
+#[derive(Clone, Debug)]
+#[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!(),
+ }
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<A, B> ExactSizeIterator for Zip<A, B>
+ where A: ExactSizeIterator, B: ExactSizeIterator {}
+
+/// An iterator that maps the values of `iter` with `f`.
+///
+/// This `struct` is created by the [`map()`] method on [`Iterator`]. See its
+/// documentation for more.
+///
+/// [`map()`]: trait.Iterator.html#method.map
+/// [`Iterator`]: trait.Iterator.html
+///
+/// # Notes about side effects
+///
+/// The [`map()`] iterator implements [`DoubleEndedIterator`], meaning that
+/// you can also [`map()`] backwards:
+///
+/// ```rust
+/// let v: Vec<i32> = vec![1, 2, 3].into_iter().rev().map(|x| x + 1).collect();
+///
+/// assert_eq!(v, [4, 3, 2]);
+/// ```
+///
+/// [`DoubleEndedIterator`]: trait.DoubleEndedIterator.html
+///
+/// But if your closure has state, iterating backwards may act in a way you do
+/// not expect. Let's go through an example. First, in the forward direction:
+///
+/// ```rust
+/// let mut c = 0;
+///
+/// for pair in vec!['a', 'b', 'c'].into_iter()
+/// .map(|letter| { c += 1; (letter, c) }) {
+/// println!("{:?}", pair);
+/// }
+/// ```
+///
+/// This will print "('a', 1), ('b', 2), ('c', 3)".
+///
+/// Now consider this twist where we add a call to `rev`. This version will
+/// print `('c', 1), ('b', 2), ('a', 3)`. Note that the letters are reversed,
+/// but the values of the counter still go in order. This is because `map()` is
+/// still being called lazilly on each item, but we are popping items off the
+/// back of the vector now, instead of shifting them from the front.
+///
+/// ```rust
+/// let mut c = 0;
+///
+/// for pair in vec!['a', 'b', 'c'].into_iter()
+/// .map(|letter| { c += 1; (letter, c) })
+/// .rev() {
+/// println!("{:?}", pair);
+/// }
+/// ```
+#[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 = "core_impl_debug", since = "1.9.0")]
+impl<I: fmt::Debug, F> fmt::Debug for Map<I, F> {
+ fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+ f.debug_struct("Map")
+ .field("iter", &self.iter)
+ .finish()
+ }
+}
+
+#[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(&mut self.f)
+ }
+
+ #[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(&mut self.f)
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<B, I: ExactSizeIterator, F> ExactSizeIterator for Map<I, F>
+ where F: FnMut(I::Item) -> B {}
+
+/// An iterator that filters the elements of `iter` with `predicate`.
+///
+/// This `struct` is created by the [`filter()`] method on [`Iterator`]. See its
+/// documentation for more.
+///
+/// [`filter()`]: trait.Iterator.html#method.filter
+/// [`Iterator`]: trait.Iterator.html
+#[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 = "core_impl_debug", since = "1.9.0")]
+impl<I: fmt::Debug, P> fmt::Debug for Filter<I, P> {
+ fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+ f.debug_struct("Filter")
+ .field("iter", &self.iter)
+ .finish()
+ }
+}
+
+#[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`.
+///
+/// This `struct` is created by the [`filter_map()`] method on [`Iterator`]. See its
+/// documentation for more.
+///
+/// [`filter_map()`]: trait.Iterator.html#method.filter_map
+/// [`Iterator`]: trait.Iterator.html
+#[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 = "core_impl_debug", since = "1.9.0")]
+impl<I: fmt::Debug, F> fmt::Debug for FilterMap<I, F> {
+ fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+ f.debug_struct("FilterMap")
+ .field("iter", &self.iter)
+ .finish()
+ }
+}
+
+#[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.
+///
+/// This `struct` is created by the [`enumerate()`] method on [`Iterator`]. See its
+/// documentation for more.
+///
+/// [`enumerate()`]: trait.Iterator.html#method.enumerate
+/// [`Iterator`]: trait.Iterator.html
+#[derive(Clone, Debug)]
+#[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);
+
+ /// # 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
+ ///
+ /// Might panic if the index of the element overflows a `usize`.
+ #[inline]
+ fn next(&mut self) -> Option<(usize, <I as Iterator>::Item)> {
+ self.iter.next().map(|a| {
+ let ret = (self.count, a);
+ // Possible undefined overflow.
+ self.count += 1;
+ ret
+ })
+ }
+
+ #[inline]
+ fn size_hint(&self) -> (usize, Option<usize>) {
+ self.iter.size_hint()
+ }
+
+ #[inline]
+ fn nth(&mut self, n: usize) -> Option<(usize, I::Item)> {
+ self.iter.nth(n).map(|a| {
+ let i = self.count + n;
+ self.count = i + 1;
+ (i, a)
+ })
+ }
+
+ #[inline]
+ fn count(self) -> usize {
+ self.iter.count()
+ }
+}
+
+#[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();
+ // Can safely add, `ExactSizeIterator` promises that the number of
+ // elements fits into a `usize`.
+ (self.count + len, a)
+ })
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<I> ExactSizeIterator for Enumerate<I> where I: ExactSizeIterator {}
+
+/// An iterator with a `peek()` that returns an optional reference to the next
+/// element.
+///
+/// This `struct` is created by the [`peekable()`] method on [`Iterator`]. See its
+/// documentation for more.
+///
+/// [`peekable()`]: trait.Iterator.html#method.peekable
+/// [`Iterator`]: trait.Iterator.html
+#[derive(Clone, Debug)]
+#[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>,
+}
+
+#[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 count(self) -> usize {
+ (if self.peeked.is_some() { 1 } else { 0 }) + self.iter.count()
+ }
+
+ #[inline]
+ fn nth(&mut self, n: usize) -> Option<I::Item> {
+ match self.peeked {
+ Some(_) if n == 0 => self.peeked.take(),
+ Some(_) => {
+ self.peeked = None;
+ self.iter.nth(n-1)
+ },
+ None => self.iter.nth(n)
+ }
+ }
+
+ #[inline]
+ fn last(self) -> Option<I::Item> {
+ self.iter.last().or(self.peeked)
+ }
+
+ #[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> {}
+
+impl<I: Iterator> Peekable<I> {
+ /// Returns a reference to the next() value without advancing the iterator.
+ ///
+ /// The `peek()` method will return the value that a call to [`next()`] would
+ /// return, but does not advance the iterator. Like [`next()`], if there is
+ /// a value, it's wrapped in a `Some(T)`, but if the iterator is over, it
+ /// will return `None`.
+ ///
+ /// [`next()`]: trait.Iterator.html#tymethod.next
+ ///
+ /// Because `peek()` returns reference, and many iterators iterate over
+ /// references, this leads to a possibly confusing situation where the
+ /// return value is a double reference. You can see this effect in the
+ /// examples below, with `&&i32`.
+ ///
+ /// # 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")]
+ 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,
+ }
+ }
+
+ /// Checks if the iterator has finished iterating.
+ ///
+ /// Returns `true` if there are no more elements in the iterator, and
+ /// `false` if there are.
+ ///
+ /// # Examples
+ ///
+ /// Basic usage:
+ ///
+ /// ```
+ /// #![feature(peekable_is_empty)]
+ ///
+ /// let xs = [1, 2, 3];
+ ///
+ /// let mut iter = xs.iter().peekable();
+ ///
+ /// // there are still elements to iterate over
+ /// assert_eq!(iter.is_empty(), false);
+ ///
+ /// // let's consume the iterator
+ /// iter.next();
+ /// iter.next();
+ /// iter.next();
+ ///
+ /// assert_eq!(iter.is_empty(), true);
+ /// ```
+ #[unstable(feature = "peekable_is_empty", issue = "32111")]
+ #[inline]
+ pub fn is_empty(&mut self) -> bool {
+ self.peek().is_none()
+ }
+}
+
+/// An iterator that rejects elements while `predicate` is true.
+///
+/// This `struct` is created by the [`skip_while()`] method on [`Iterator`]. See its
+/// documentation for more.
+///
+/// [`skip_while()`]: trait.Iterator.html#method.skip_while
+/// [`Iterator`]: trait.Iterator.html
+#[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 = "core_impl_debug", since = "1.9.0")]
+impl<I: fmt::Debug, P> fmt::Debug for SkipWhile<I, P> {
+ fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+ f.debug_struct("SkipWhile")
+ .field("iter", &self.iter)
+ .field("flag", &self.flag)
+ .finish()
+ }
+}
+
+#[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.
+///
+/// This `struct` is created by the [`take_while()`] method on [`Iterator`]. See its
+/// documentation for more.
+///
+/// [`take_while()`]: trait.Iterator.html#method.take_while
+/// [`Iterator`]: trait.Iterator.html
+#[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 = "core_impl_debug", since = "1.9.0")]
+impl<I: fmt::Debug, P> fmt::Debug for TakeWhile<I, P> {
+ fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+ f.debug_struct("TakeWhile")
+ .field("iter", &self.iter)
+ .field("flag", &self.flag)
+ .finish()
+ }
+}
+
+#[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`.
+///
+/// This `struct` is created by the [`skip()`] method on [`Iterator`]. See its
+/// documentation for more.
+///
+/// [`skip()`]: trait.Iterator.html#method.skip
+/// [`Iterator`]: trait.Iterator.html
+#[derive(Clone, Debug)]
+#[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::Item> {
+ if self.n == 0 {
+ self.iter.next()
+ } else {
+ let old_n = self.n;
+ self.n = 0;
+ self.iter.nth(old_n)
+ }
+ }
+
+ #[inline]
+ fn nth(&mut self, n: usize) -> Option<I::Item> {
+ // Can't just add n + self.n due to overflow.
+ if self.n == 0 {
+ self.iter.nth(n)
+ } else {
+ let to_skip = self.n;
+ self.n = 0;
+ // nth(n) skips n+1
+ if self.iter.nth(to_skip-1).is_none() {
+ return None;
+ }
+ self.iter.nth(n)
+ }
+ }
+
+ #[inline]
+ fn count(self) -> usize {
+ self.iter.count().saturating_sub(self.n)
+ }
+
+ #[inline]
+ fn last(mut self) -> Option<I::Item> {
+ if self.n == 0 {
+ self.iter.last()
+ } else {
+ let next = self.next();
+ if next.is_some() {
+ // recurse. n should be 0.
+ self.last().or(next)
+ } else {
+ None
+ }
+ }
+ }
+
+ #[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)
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<I> ExactSizeIterator for Skip<I> where I: ExactSizeIterator {}
+
+#[stable(feature = "double_ended_skip_iterator", since = "1.8.0")]
+impl<I> DoubleEndedIterator for Skip<I> where I: DoubleEndedIterator + ExactSizeIterator {
+ fn next_back(&mut self) -> Option<Self::Item> {
+ if self.len() > 0 {
+ self.iter.next_back()
+ } else {
+ None
+ }
+ }
+}
+
+/// An iterator that only iterates over the first `n` iterations of `iter`.
+///
+/// This `struct` is created by the [`take()`] method on [`Iterator`]. See its
+/// documentation for more.
+///
+/// [`take()`]: trait.Iterator.html#method.take
+/// [`Iterator`]: trait.Iterator.html
+#[derive(Clone, Debug)]
+#[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 nth(&mut self, n: usize) -> Option<I::Item> {
+ if self.n > n {
+ self.n -= n + 1;
+ self.iter.nth(n)
+ } else {
+ if self.n > 0 {
+ self.iter.nth(self.n - 1);
+ self.n = 0;
+ }
+ 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)
+ }
+}
+
+#[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.
+///
+/// This `struct` is created by the [`scan()`] method on [`Iterator`]. See its
+/// documentation for more.
+///
+/// [`scan()`]: trait.Iterator.html#method.scan
+/// [`Iterator`]: trait.Iterator.html
+#[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,
+ state: St,
+}
+
+#[stable(feature = "core_impl_debug", since = "1.9.0")]
+impl<I: fmt::Debug, St: fmt::Debug, F> fmt::Debug for Scan<I, St, F> {
+ fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+ f.debug_struct("Scan")
+ .field("iter", &self.iter)
+ .field("state", &self.state)
+ .finish()
+ }
+}
+
+#[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.
+///
+/// This `struct` is created by the [`flat_map()`] method on [`Iterator`]. See its
+/// documentation for more.
+///
+/// [`flat_map()`]: trait.Iterator.html#method.flat_map
+/// [`Iterator`]: trait.Iterator.html
+#[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: IntoIterator, F> {
+ iter: I,
+ f: F,
+ frontiter: Option<U::IntoIter>,
+ backiter: Option<U::IntoIter>,
+}
+
+#[stable(feature = "core_impl_debug", since = "1.9.0")]
+impl<I: fmt::Debug, U: IntoIterator, F> fmt::Debug for FlatMap<I, U, F>
+ where U::IntoIter: fmt::Debug
+{
+ fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+ f.debug_struct("FlatMap")
+ .field("iter", &self.iter)
+ .field("frontiter", &self.frontiter)
+ .field("backiter", &self.backiter)
+ .finish()
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<I: Iterator, U: IntoIterator, 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 {
+ if let Some(x) = inner.by_ref().next() {
+ return Some(x)
+ }
+ }
+ match self.iter.next().map(&mut self.f) {
+ None => return self.backiter.as_mut().and_then(|it| it.next()),
+ next => self.frontiter = next.map(IntoIterator::into_iter),
+ }
+ }
+ }
+
+ #[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, F> DoubleEndedIterator for FlatMap<I, U, F> where
+ F: FnMut(I::Item) -> U,
+ U: IntoIterator,
+ U::IntoIter: DoubleEndedIterator
+{
+ #[inline]
+ fn next_back(&mut self) -> Option<U::Item> {
+ loop {
+ if let Some(ref mut inner) = self.backiter {
+ if let Some(y) = inner.next_back() {
+ return Some(y)
+ }
+ }
+ match self.iter.next_back().map(&mut self.f) {
+ None => return self.frontiter.as_mut().and_then(|it| it.next_back()),
+ next => self.backiter = next.map(IntoIterator::into_iter),
+ }
+ }
+ }
+}
+
+/// An iterator that yields `None` forever after the underlying iterator
+/// yields `None` once.
+///
+/// This `struct` is created by the [`fuse()`] method on [`Iterator`]. See its
+/// documentation for more.
+///
+/// [`fuse()`]: trait.Iterator.html#method.fuse
+/// [`Iterator`]: trait.Iterator.html
+#[derive(Clone, Debug)]
+#[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 {
+ let next = self.iter.next();
+ self.done = next.is_none();
+ next
+ }
+ }
+
+ #[inline]
+ fn nth(&mut self, n: usize) -> Option<I::Item> {
+ if self.done {
+ None
+ } else {
+ let nth = self.iter.nth(n);
+ self.done = nth.is_none();
+ nth
+ }
+ }
+
+ #[inline]
+ fn last(self) -> Option<I::Item> {
+ if self.done {
+ None
+ } else {
+ self.iter.last()
+ }
+ }
+
+ #[inline]
+ fn count(self) -> usize {
+ if self.done {
+ 0
+ } else {
+ self.iter.count()
+ }
+ }
+
+ #[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 {
+ let next = self.iter.next_back();
+ self.done = next.is_none();
+ next
+ }
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<I> ExactSizeIterator for Fuse<I> where I: ExactSizeIterator {}
+
+/// An iterator that calls a function with a reference to each element before
+/// yielding it.
+///
+/// This `struct` is created by the [`inspect()`] method on [`Iterator`]. See its
+/// documentation for more.
+///
+/// [`inspect()`]: trait.Iterator.html#method.inspect
+/// [`Iterator`]: trait.Iterator.html
+#[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,
+}
+
+#[stable(feature = "core_impl_debug", since = "1.9.0")]
+impl<I: fmt::Debug, F> fmt::Debug for Inspect<I, F> {
+ fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+ f.debug_struct("Inspect")
+ .field("iter", &self.iter)
+ .finish()
+ }
+}
+
+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)
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<I: ExactSizeIterator, F> ExactSizeIterator for Inspect<I, F>
+ where F: FnMut(&I::Item) {}
diff --git a/libcore/iter/range.rs b/libcore/iter/range.rs
new file mode 100644
index 0000000..0814356
--- /dev/null
+++ b/libcore/iter/range.rs
@@ -0,0 +1,548 @@
+// Copyright 2013-2016 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.
+
+use clone::Clone;
+use cmp::PartialOrd;
+use mem;
+use num::{Zero, One};
+use ops::{self, Add, Sub};
+use option::Option::{self, Some, None};
+use marker::Sized;
+use usize;
+
+use super::{DoubleEndedIterator, ExactSizeIterator, Iterator};
+
+/// 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",
+ issue = "27741")]
+pub trait Step: PartialOrd + Sized {
+ /// Steps `self` if possible.
+ fn step(&self, by: &Self) -> Option<Self>;
+
+ /// Returns the number of steps between two step objects. The count is
+ /// inclusive of `start` and exclusive of `end`.
+ ///
+ /// Returns `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_unsigned {
+ ($($t:ty)*) => ($(
+ #[unstable(feature = "step_trait",
+ reason = "likely to be replaced by finer-grained traits",
+ issue = "27741")]
+ 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 *by == 0 { return None; }
+ if *start < *end {
+ // Note: We assume $t <= usize here
+ let diff = (*end - *start) as usize;
+ let by = *by as usize;
+ if diff % by > 0 {
+ Some(diff / by + 1)
+ } else {
+ Some(diff / by)
+ }
+ } else {
+ Some(0)
+ }
+ }
+ }
+ )*)
+}
+macro_rules! step_impl_signed {
+ ($($t:ty)*) => ($(
+ #[unstable(feature = "step_trait",
+ reason = "likely to be replaced by finer-grained traits",
+ issue = "27741")]
+ 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 *by == 0 { return None; }
+ let diff: usize;
+ let by_u: usize;
+ if *by > 0 {
+ if *start >= *end {
+ return Some(0);
+ }
+ // Note: We assume $t <= isize here
+ // Use .wrapping_sub and cast to usize to compute the
+ // difference that may not fit inside the range of isize.
+ diff = (*end as isize).wrapping_sub(*start as isize) as usize;
+ by_u = *by as usize;
+ } else {
+ if *start <= *end {
+ return Some(0);
+ }
+ diff = (*start as isize).wrapping_sub(*end as isize) as usize;
+ by_u = (*by as isize).wrapping_mul(-1) as usize;
+ }
+ if diff % by_u > 0 {
+ Some(diff / by_u + 1)
+ } else {
+ Some(diff / by_u)
+ }
+ }
+ }
+ )*)
+}
+
+macro_rules! step_impl_no_between {
+ ($($t:ty)*) => ($(
+ #[unstable(feature = "step_trait",
+ reason = "likely to be replaced by finer-grained traits",
+ issue = "27741")]
+ 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_unsigned!(usize u8 u16 u32);
+step_impl_signed!(isize i8 i16 i32);
+#[cfg(target_pointer_width = "64")]
+step_impl_unsigned!(u64);
+#[cfg(target_pointer_width = "64")]
+step_impl_signed!(i64);
+// If the target pointer width is not 64-bits, we
+// assume here that it is less than 64-bits.
+#[cfg(not(target_pointer_width = "64"))]
+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, RangeInclusive}`.
+#[derive(Clone, Debug)]
+#[unstable(feature = "step_by", reason = "recent addition",
+ issue = "27741")]
+pub struct StepBy<A, R> {
+ step_by: A,
+ range: R,
+}
+
+impl<A: Step> ops::RangeFrom<A> {
+ /// Creates an iterator starting at the same point, but stepping by
+ /// the given amount at each iteration.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// # #![feature(step_by)]
+ ///
+ /// for i in (0u8..).step_by(2).take(10) {
+ /// println!("{}", i);
+ /// }
+ /// ```
+ ///
+ /// This prints the first ten even natural integers (0 to 18).
+ #[unstable(feature = "step_by", reason = "recent addition",
+ issue = "27741")]
+ pub fn step_by(self, by: A) -> StepBy<A, Self> {
+ StepBy {
+ step_by: by,
+ range: self
+ }
+ }
+}
+
+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)]
+ ///
+ /// 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",
+ issue = "27741")]
+ pub fn step_by(self, by: A) -> StepBy<A, Self> {
+ StepBy {
+ step_by: by,
+ range: self
+ }
+ }
+}
+
+impl<A: Step> ops::RangeInclusive<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, inclusive_range_syntax)]
+ ///
+ /// for i in (0...10).step_by(2) {
+ /// println!("{}", i);
+ /// }
+ /// ```
+ ///
+ /// This prints:
+ ///
+ /// ```text
+ /// 0
+ /// 2
+ /// 4
+ /// 6
+ /// 8
+ /// 10
+ /// ```
+ #[unstable(feature = "step_by", reason = "recent addition",
+ issue = "27741")]
+ 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, ops::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
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+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
+ }
+ }
+
+ #[inline]
+ fn size_hint(&self) -> (usize, Option<usize>) {
+ match Step::steps_between(&self.range.start,
+ &self.range.end,
+ &self.step_by) {
+ Some(hint) => (hint, Some(hint)),
+ None => (0, None)
+ }
+ }
+}
+
+#[unstable(feature = "inclusive_range",
+ reason = "recently added, follows RFC",
+ issue = "28237")]
+impl<A: Step + Zero + Clone> Iterator for StepBy<A, ops::RangeInclusive<A>> {
+ type Item = A;
+
+ #[inline]
+ fn next(&mut self) -> Option<A> {
+ use ops::RangeInclusive::*;
+
+ // this function has a sort of odd structure due to borrowck issues
+ // we may need to replace self.range, so borrows of start and end need to end early
+
+ let (finishing, n) = match self.range {
+ Empty { .. } => return None, // empty iterators yield no values
+
+ NonEmpty { ref mut start, ref mut end } => {
+ let zero = A::zero();
+ let rev = self.step_by < zero;
+
+ // march start towards (maybe past!) end and yield the old value
+ if (rev && start >= end) ||
+ (!rev && start <= end)
+ {
+ match start.step(&self.step_by) {
+ Some(mut n) => {
+ mem::swap(start, &mut n);
+ (None, Some(n)) // yield old value, remain non-empty
+ },
+ None => {
+ let mut n = end.clone();
+ mem::swap(start, &mut n);
+ (None, Some(n)) // yield old value, remain non-empty
+ }
+ }
+ } else {
+ // found range in inconsistent state (start at or past end), so become empty
+ (Some(mem::replace(end, zero)), None)
+ }
+ }
+ };
+
+ // turn into an empty iterator if we've reached the end
+ if let Some(end) = finishing {
+ self.range = Empty { at: end };
+ }
+
+ n
+ }
+
+ #[inline]
+ fn size_hint(&self) -> (usize, Option<usize>) {
+ use ops::RangeInclusive::*;
+
+ match self.range {
+ Empty { .. } => (0, Some(0)),
+
+ NonEmpty { ref start, ref end } =>
+ match Step::steps_between(start,
+ end,
+ &self.step_by) {
+ Some(hint) => (hint.saturating_add(1), hint.checked_add(1)),
+ None => (0, None)
+ }
+ }
+ }
+}
+
+macro_rules! range_exact_iter_impl {
+ ($($t:ty)*) => ($(
+ #[stable(feature = "rust1", since = "1.0.0")]
+ impl ExactSizeIterator for ops::Range<$t> { }
+
+ #[unstable(feature = "inclusive_range",
+ reason = "recently added, follows RFC",
+ issue = "28237")]
+ impl ExactSizeIterator for ops::RangeInclusive<$t> { }
+ )*)
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<A: Step + One> Iterator for ops::Range<A> where
+ for<'a> &'a A: Add<&'a A, Output = A>
+{
+ type Item = A;
+
+ #[inline]
+ fn next(&mut self) -> Option<A> {
+ if self.start < self.end {
+ let mut n = &self.start + &A::one();
+ 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")]
+impl<A: Step + One + Clone> DoubleEndedIterator for ops::Range<A> where
+ for<'a> &'a A: Add<&'a A, Output = A>,
+ 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")]
+impl<A: Step + One> Iterator for ops::RangeFrom<A> where
+ for<'a> &'a A: Add<&'a A, Output = A>
+{
+ type Item = A;
+
+ #[inline]
+ fn next(&mut self) -> Option<A> {
+ let mut n = &self.start + &A::one();
+ mem::swap(&mut n, &mut self.start);
+ Some(n)
+ }
+}
+
+#[unstable(feature = "inclusive_range", reason = "recently added, follows RFC", issue = "28237")]
+impl<A: Step + One> Iterator for ops::RangeInclusive<A> where
+ for<'a> &'a A: Add<&'a A, Output = A>
+{
+ type Item = A;
+
+ #[inline]
+ fn next(&mut self) -> Option<A> {
+ use ops::RangeInclusive::*;
+
+ // this function has a sort of odd structure due to borrowck issues
+ // we may need to replace self, so borrows of self.start and self.end need to end early
+
+ let (finishing, n) = match *self {
+ Empty { .. } => (None, None), // empty iterators yield no values
+
+ NonEmpty { ref mut start, ref mut end } => {
+ if start == end {
+ (Some(mem::replace(end, A::one())), Some(mem::replace(start, A::one())))
+ } else if start < end {
+ let one = A::one();
+ let mut n = &*start + &one;
+ mem::swap(&mut n, start);
+
+ // if the iterator is done iterating, it will change from NonEmpty to Empty
+ // to avoid unnecessary drops or clones, we'll reuse either start or end
+ // (they are equal now, so it doesn't matter which)
+ // to pull out end, we need to swap something back in -- use the previously
+ // created A::one() as a dummy value
+
+ (if n == *end { Some(mem::replace(end, one)) } else { None },
+ // ^ are we done yet?
+ Some(n)) // < the value to output
+ } else {
+ (Some(mem::replace(start, A::one())), None)
+ }
+ }
+ };
+
+ // turn into an empty iterator if this is the last value
+ if let Some(end) = finishing {
+ *self = Empty { at: end };
+ }
+
+ n
+ }
+
+ #[inline]
+ fn size_hint(&self) -> (usize, Option<usize>) {
+ use ops::RangeInclusive::*;
+
+ match *self {
+ Empty { .. } => (0, Some(0)),
+
+ NonEmpty { ref start, ref end } =>
+ match Step::steps_between(start, end, &A::one()) {
+ Some(hint) => (hint.saturating_add(1), hint.checked_add(1)),
+ None => (0, None),
+ }
+ }
+ }
+}
+
+#[unstable(feature = "inclusive_range", reason = "recently added, follows RFC", issue = "28237")]
+impl<A: Step + One> DoubleEndedIterator for ops::RangeInclusive<A> where
+ for<'a> &'a A: Add<&'a A, Output = A>,
+ for<'a> &'a A: Sub<&'a A, Output = A>
+{
+ #[inline]
+ fn next_back(&mut self) -> Option<A> {
+ use ops::RangeInclusive::*;
+
+ // see Iterator::next for comments
+
+ let (finishing, n) = match *self {
+ Empty { .. } => return None,
+
+ NonEmpty { ref mut start, ref mut end } => {
+ if start == end {
+ (Some(mem::replace(start, A::one())), Some(mem::replace(end, A::one())))
+ } else if start < end {
+ let one = A::one();
+ let mut n = &*end - &one;
+ mem::swap(&mut n, end);
+
+ (if n == *start { Some(mem::replace(start, one)) } else { None },
+ Some(n))
+ } else {
+ (Some(mem::replace(end, A::one())), None)
+ }
+ }
+ };
+
+ if let Some(start) = finishing {
+ *self = Empty { at: start };
+ }
+
+ n
+ }
+}
+
diff --git a/libcore/iter/sources.rs b/libcore/iter/sources.rs
new file mode 100644
index 0000000..ecd4a78
--- /dev/null
+++ b/libcore/iter/sources.rs
@@ -0,0 +1,270 @@
+// Copyright 2013-2016 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.
+
+use clone::Clone;
+use default::Default;
+use fmt;
+use marker;
+use option::Option::{self, Some, None};
+use usize;
+
+use super::{DoubleEndedIterator, IntoIterator, Iterator, ExactSizeIterator};
+
+/// An iterator that repeats an element endlessly.
+///
+/// This `struct` is created by the [`repeat()`] function. See its documentation for more.
+///
+/// [`repeat()`]: fn.repeat.html
+#[derive(Clone, Debug)]
+#[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> { Some(self.element.clone()) }
+ #[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> { Some(self.element.clone()) }
+}
+
+/// Creates a new iterator that endlessly repeats a single element.
+///
+/// The `repeat()` function repeats a single value over and over and over and
+/// over and over and 🔁.
+///
+/// Infinite iterators like `repeat()` are often used with adapters like
+/// [`take()`], in order to make them finite.
+///
+/// [`take()`]: trait.Iterator.html#method.take
+///
+/// # Examples
+///
+/// Basic usage:
+///
+/// ```
+/// use std::iter;
+///
+/// // the number four 4ever:
+/// let mut fours = iter::repeat(4);
+///
+/// assert_eq!(Some(4), fours.next());
+/// assert_eq!(Some(4), fours.next());
+/// assert_eq!(Some(4), fours.next());
+/// assert_eq!(Some(4), fours.next());
+/// assert_eq!(Some(4), fours.next());
+///
+/// // yup, still four
+/// assert_eq!(Some(4), fours.next());
+/// ```
+///
+/// Going finite with [`take()`]:
+///
+/// ```
+/// use std::iter;
+///
+/// // that last example was too many fours. Let's only have four fours.
+/// let mut four_fours = iter::repeat(4).take(4);
+///
+/// assert_eq!(Some(4), four_fours.next());
+/// assert_eq!(Some(4), four_fours.next());
+/// assert_eq!(Some(4), four_fours.next());
+/// assert_eq!(Some(4), four_fours.next());
+///
+/// // ... and now we're done
+/// assert_eq!(None, four_fours.next());
+/// ```
+#[inline]
+#[stable(feature = "rust1", since = "1.0.0")]
+pub fn repeat<T: Clone>(elt: T) -> Repeat<T> {
+ Repeat{element: elt}
+}
+
+/// An iterator that yields nothing.
+///
+/// This `struct` is created by the [`empty()`] function. See its documentation for more.
+///
+/// [`empty()`]: fn.empty.html
+#[stable(feature = "iter_empty", since = "1.2.0")]
+pub struct Empty<T>(marker::PhantomData<T>);
+
+#[stable(feature = "core_impl_debug", since = "1.9.0")]
+impl<T> fmt::Debug for Empty<T> {
+ fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+ f.pad("Empty")
+ }
+}
+
+#[stable(feature = "iter_empty", since = "1.2.0")]
+impl<T> Iterator for Empty<T> {
+ type Item = T;
+
+ fn next(&mut self) -> Option<T> {
+ None
+ }
+
+ fn size_hint(&self) -> (usize, Option<usize>){
+ (0, Some(0))
+ }
+}
+
+#[stable(feature = "iter_empty", since = "1.2.0")]
+impl<T> DoubleEndedIterator for Empty<T> {
+ fn next_back(&mut self) -> Option<T> {
+ None
+ }
+}
+
+#[stable(feature = "iter_empty", since = "1.2.0")]
+impl<T> ExactSizeIterator for Empty<T> {
+ fn len(&self) -> usize {
+ 0
+ }
+}
+
+// not #[derive] because that adds a Clone bound on T,
+// which isn't necessary.
+#[stable(feature = "iter_empty", since = "1.2.0")]
+impl<T> Clone for Empty<T> {
+ fn clone(&self) -> Empty<T> {
+ Empty(marker::PhantomData)
+ }
+}
+
+// not #[derive] because that adds a Default bound on T,
+// which isn't necessary.
+#[stable(feature = "iter_empty", since = "1.2.0")]
+impl<T> Default for Empty<T> {
+ fn default() -> Empty<T> {
+ Empty(marker::PhantomData)
+ }
+}
+
+/// Creates an iterator that yields nothing.
+///
+/// # Examples
+///
+/// Basic usage:
+///
+/// ```
+/// use std::iter;
+///
+/// // this could have been an iterator over i32, but alas, it's just not.
+/// let mut nope = iter::empty::<i32>();
+///
+/// assert_eq!(None, nope.next());
+/// ```
+#[stable(feature = "iter_empty", since = "1.2.0")]
+pub fn empty<T>() -> Empty<T> {
+ Empty(marker::PhantomData)
+}
+
+/// An iterator that yields an element exactly once.
+///
+/// This `struct` is created by the [`once()`] function. See its documentation for more.
+///
+/// [`once()`]: fn.once.html
+#[derive(Clone, Debug)]
+#[stable(feature = "iter_once", since = "1.2.0")]
+pub struct Once<T> {
+ inner: ::option::IntoIter<T>
+}
+
+#[stable(feature = "iter_once", since = "1.2.0")]
+impl<T> Iterator for Once<T> {
+ type Item = T;
+
+ fn next(&mut self) -> Option<T> {
+ self.inner.next()
+ }
+
+ fn size_hint(&self) -> (usize, Option<usize>) {
+ self.inner.size_hint()
+ }
+}
+
+#[stable(feature = "iter_once", since = "1.2.0")]
+impl<T> DoubleEndedIterator for Once<T> {
+ fn next_back(&mut self) -> Option<T> {
+ self.inner.next_back()
+ }
+}
+
+#[stable(feature = "iter_once", since = "1.2.0")]
+impl<T> ExactSizeIterator for Once<T> {
+ fn len(&self) -> usize {
+ self.inner.len()
+ }
+}
+
+/// Creates an iterator that yields an element exactly once.
+///
+/// This is commonly used to adapt a single value into a [`chain()`] of other
+/// kinds of iteration. Maybe you have an iterator that covers almost
+/// everything, but you need an extra special case. Maybe you have a function
+/// which works on iterators, but you only need to process one value.
+///
+/// [`chain()`]: trait.Iterator.html#method.chain
+///
+/// # Examples
+///
+/// Basic usage:
+///
+/// ```
+/// use std::iter;
+///
+/// // one is the loneliest number
+/// let mut one = iter::once(1);
+///
+/// assert_eq!(Some(1), one.next());
+///
+/// // just one, that's all we get
+/// assert_eq!(None, one.next());
+/// ```
+///
+/// Chaining together with another iterator. Let's say that we want to iterate
+/// over each file of the `.foo` directory, but also a configuration file,
+/// `.foorc`:
+///
+/// ```no_run
+/// use std::iter;
+/// use std::fs;
+/// use std::path::PathBuf;
+///
+/// let dirs = fs::read_dir(".foo").unwrap();
+///
+/// // we need to convert from an iterator of DirEntry-s to an iterator of
+/// // PathBufs, so we use map
+/// let dirs = dirs.map(|file| file.unwrap().path());
+///
+/// // now, our iterator just for our config file
+/// let config = iter::once(PathBuf::from(".foorc"));
+///
+/// // chain the two iterators together into one big iterator
+/// let files = dirs.chain(config);
+///
+/// // this will give us all of the files in .foo as well as .foorc
+/// for f in files {
+/// println!("{:?}", f);
+/// }
+/// ```
+#[stable(feature = "iter_once", since = "1.2.0")]
+pub fn once<T>(value: T) -> Once<T> {
+ Once { inner: Some(value).into_iter() }
+}
diff --git a/libcore/iter/traits.rs b/libcore/iter/traits.rs
new file mode 100644
index 0000000..6750398
--- /dev/null
+++ b/libcore/iter/traits.rs
@@ -0,0 +1,526 @@
+// Copyright 2013-2016 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.
+
+use option::Option::{self, Some};
+use marker::Sized;
+
+use super::Iterator;
+
+/// Conversion from an `Iterator`.
+///
+/// By implementing `FromIterator` for a type, you define how it will be
+/// created from an iterator. This is common for types which describe a
+/// collection of some kind.
+///
+/// `FromIterator`'s [`from_iter()`] is rarely called explicitly, and is instead
+/// used through [`Iterator`]'s [`collect()`] method. See [`collect()`]'s
+/// documentation for more examples.
+///
+/// [`from_iter()`]: #tymethod.from_iter
+/// [`Iterator`]: trait.Iterator.html
+/// [`collect()`]: trait.Iterator.html#method.collect
+///
+/// See also: [`IntoIterator`].
+///
+/// [`IntoIterator`]: trait.IntoIterator.html
+///
+/// # Examples
+///
+/// Basic usage:
+///
+/// ```
+/// use std::iter::FromIterator;
+///
+/// let five_fives = std::iter::repeat(5).take(5);
+///
+/// let v = Vec::from_iter(five_fives);
+///
+/// assert_eq!(v, vec![5, 5, 5, 5, 5]);
+/// ```
+///
+/// Using [`collect()`] to implicitly use `FromIterator`:
+///
+/// ```
+/// let five_fives = std::iter::repeat(5).take(5);
+///
+/// let v: Vec<i32> = five_fives.collect();
+///
+/// assert_eq!(v, vec![5, 5, 5, 5, 5]);
+/// ```
+///
+/// Implementing `FromIterator` for your type:
+///
+/// ```
+/// use std::iter::FromIterator;
+///
+/// // A sample collection, that's just a wrapper over Vec<T>
+/// #[derive(Debug)]
+/// struct MyCollection(Vec<i32>);
+///
+/// // Let's give it some methods so we can create one and add things
+/// // to it.
+/// impl MyCollection {
+/// fn new() -> MyCollection {
+/// MyCollection(Vec::new())
+/// }
+///
+/// fn add(&mut self, elem: i32) {
+/// self.0.push(elem);
+/// }
+/// }
+///
+/// // and we'll implement FromIterator
+/// impl FromIterator<i32> for MyCollection {
+/// fn from_iter<I: IntoIterator<Item=i32>>(iter: I) -> Self {
+/// let mut c = MyCollection::new();
+///
+/// for i in iter {
+/// c.add(i);
+/// }
+///
+/// c
+/// }
+/// }
+///
+/// // Now we can make a new iterator...
+/// let iter = (0..5).into_iter();
+///
+/// // ... and make a MyCollection out of it
+/// let c = MyCollection::from_iter(iter);
+///
+/// assert_eq!(c.0, vec![0, 1, 2, 3, 4]);
+///
+/// // collect works too!
+///
+/// let iter = (0..5).into_iter();
+/// let c: MyCollection = iter.collect();
+///
+/// assert_eq!(c.0, vec![0, 1, 2, 3, 4]);
+/// ```
+#[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>: Sized {
+ /// Creates a value from an iterator.
+ ///
+ /// See the [module-level documentation] for more.
+ ///
+ /// [module-level documentation]: trait.FromIterator.html
+ ///
+ /// # Examples
+ ///
+ /// Basic usage:
+ ///
+ /// ```
+ /// use std::iter::FromIterator;
+ ///
+ /// let five_fives = std::iter::repeat(5).take(5);
+ ///
+ /// let v = Vec::from_iter(five_fives);
+ ///
+ /// assert_eq!(v, vec![5, 5, 5, 5, 5]);
+ /// ```
+ #[stable(feature = "rust1", since = "1.0.0")]
+ fn from_iter<T: IntoIterator<Item=A>>(iter: T) -> Self;
+}
+
+/// Conversion into an `Iterator`.
+///
+/// By implementing `IntoIterator` for a type, you define how it will be
+/// converted to an iterator. This is common for types which describe a
+/// collection of some kind.
+///
+/// One benefit of implementing `IntoIterator` is that your type will [work
+/// with Rust's `for` loop syntax](index.html#for-loops-and-intoiterator).
+///
+/// See also: [`FromIterator`].
+///
+/// [`FromIterator`]: trait.FromIterator.html
+///
+/// # Examples
+///
+/// Basic usage:
+///
+/// ```
+/// let v = vec![1, 2, 3];
+///
+/// let mut iter = v.into_iter();
+///
+/// let n = iter.next();
+/// assert_eq!(Some(1), n);
+///
+/// let n = iter.next();
+/// assert_eq!(Some(2), n);
+///
+/// let n = iter.next();
+/// assert_eq!(Some(3), n);
+///
+/// let n = iter.next();
+/// assert_eq!(None, n);
+/// ```
+///
+/// Implementing `IntoIterator` for your type:
+///
+/// ```
+/// // A sample collection, that's just a wrapper over Vec<T>
+/// #[derive(Debug)]
+/// struct MyCollection(Vec<i32>);
+///
+/// // Let's give it some methods so we can create one and add things
+/// // to it.
+/// impl MyCollection {
+/// fn new() -> MyCollection {
+/// MyCollection(Vec::new())
+/// }
+///
+/// fn add(&mut self, elem: i32) {
+/// self.0.push(elem);
+/// }
+/// }
+///
+/// // and we'll implement IntoIterator
+/// impl IntoIterator for MyCollection {
+/// type Item = i32;
+/// type IntoIter = ::std::vec::IntoIter<i32>;
+///
+/// fn into_iter(self) -> Self::IntoIter {
+/// self.0.into_iter()
+/// }
+/// }
+///
+/// // Now we can make a new collection...
+/// let mut c = MyCollection::new();
+///
+/// // ... add some stuff to it ...
+/// c.add(0);
+/// c.add(1);
+/// c.add(2);
+///
+/// // ... and then turn it into an Iterator:
+/// for (i, n) in c.into_iter().enumerate() {
+/// assert_eq!(i as i32, n);
+/// }
+/// ```
+#[stable(feature = "rust1", since = "1.0.0")]
+pub trait IntoIterator {
+ /// The type of the elements being iterated over.
+ #[stable(feature = "rust1", since = "1.0.0")]
+ type Item;
+
+ /// Which kind of iterator are we turning this into?
+ #[stable(feature = "rust1", since = "1.0.0")]
+ type IntoIter: Iterator<Item=Self::Item>;
+
+ /// Creates an iterator from a value.
+ ///
+ /// See the [module-level documentation] for more.
+ ///
+ /// [module-level documentation]: trait.IntoIterator.html
+ ///
+ /// # Examples
+ ///
+ /// Basic usage:
+ ///
+ /// ```
+ /// let v = vec![1, 2, 3];
+ ///
+ /// let mut iter = v.into_iter();
+ ///
+ /// let n = iter.next();
+ /// assert_eq!(Some(1), n);
+ ///
+ /// let n = iter.next();
+ /// assert_eq!(Some(2), n);
+ ///
+ /// let n = iter.next();
+ /// assert_eq!(Some(3), n);
+ ///
+ /// let n = iter.next();
+ /// assert_eq!(None, n);
+ /// ```
+ #[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
+ }
+}
+
+/// Extend a collection with the contents of an iterator.
+///
+/// Iterators produce a series of values, and collections can also be thought
+/// of as a series of values. The `Extend` trait bridges this gap, allowing you
+/// to extend a collection by including the contents of that iterator.
+///
+/// # Examples
+///
+/// Basic usage:
+///
+/// ```
+/// // You can extend a String with some chars:
+/// let mut message = String::from("The first three letters are: ");
+///
+/// message.extend(&['a', 'b', 'c']);
+///
+/// assert_eq!("abc", &message[29..32]);
+/// ```
+///
+/// Implementing `Extend`:
+///
+/// ```
+/// // A sample collection, that's just a wrapper over Vec<T>
+/// #[derive(Debug)]
+/// struct MyCollection(Vec<i32>);
+///
+/// // Let's give it some methods so we can create one and add things
+/// // to it.
+/// impl MyCollection {
+/// fn new() -> MyCollection {
+/// MyCollection(Vec::new())
+/// }
+///
+/// fn add(&mut self, elem: i32) {
+/// self.0.push(elem);
+/// }
+/// }
+///
+/// // since MyCollection has a list of i32s, we implement Extend for i32
+/// impl Extend<i32> for MyCollection {
+///
+/// // This is a bit simpler with the concrete type signature: we can call
+/// // extend on anything which can be turned into an Iterator which gives
+/// // us i32s. Because we need i32s to put into MyCollection.
+/// fn extend<T: IntoIterator<Item=i32>>(&mut self, iter: T) {
+///
+/// // The implementation is very straightforward: loop through the
+/// // iterator, and add() each element to ourselves.
+/// for elem in iter {
+/// self.add(elem);
+/// }
+/// }
+/// }
+///
+/// let mut c = MyCollection::new();
+///
+/// c.add(5);
+/// c.add(6);
+/// c.add(7);
+///
+/// // let's extend our collection with three more numbers
+/// c.extend(vec![1, 2, 3]);
+///
+/// // we've added these elements onto the end
+/// assert_eq!("MyCollection([5, 6, 7, 1, 2, 3])", format!("{:?}", c));
+/// ```
+#[stable(feature = "rust1", since = "1.0.0")]
+pub trait Extend<A> {
+ /// Extends a collection with the contents of an iterator.
+ ///
+ /// As this is the only method for this trait, the [trait-level] docs
+ /// contain more details.
+ ///
+ /// [trait-level]: trait.Extend.html
+ ///
+ /// # Examples
+ ///
+ /// Basic usage:
+ ///
+ /// ```
+ /// // You can extend a String with some chars:
+ /// let mut message = String::from("abc");
+ ///
+ /// message.extend(['d', 'e', 'f'].iter());
+ ///
+ /// assert_eq!("abcdef", &message);
+ /// ```
+ #[stable(feature = "rust1", since = "1.0.0")]
+ fn extend<T: IntoIterator<Item=A>>(&mut self, iter: T);
+}
+
+/// An iterator able to yield elements from both ends.
+///
+/// Something that implements `DoubleEndedIterator` has one extra capability
+/// over something that implements [`Iterator`]: the ability to also take
+/// `Item`s from the back, as well as the front.
+///
+/// It is important to note that both back and forth work on the same range,
+/// and do not cross: iteration is over when they meet in the middle.
+///
+/// In a similar fashion to the [`Iterator`] protocol, once a
+/// `DoubleEndedIterator` returns `None` from a `next_back()`, calling it again
+/// may or may not ever return `Some` again. `next()` and `next_back()` are
+/// interchangable for this purpose.
+///
+/// [`Iterator`]: trait.Iterator.html
+///
+/// # Examples
+///
+/// Basic usage:
+///
+/// ```
+/// let numbers = vec![1, 2, 3];
+///
+/// let mut iter = numbers.iter();
+///
+/// assert_eq!(Some(&1), iter.next());
+/// assert_eq!(Some(&3), iter.next_back());
+/// assert_eq!(Some(&2), iter.next_back());
+/// assert_eq!(None, iter.next());
+/// assert_eq!(None, iter.next_back());
+/// ```
+#[stable(feature = "rust1", since = "1.0.0")]
+pub trait DoubleEndedIterator: Iterator {
+ /// An iterator able to yield elements from both ends.
+ ///
+ /// As this is the only method for this trait, the [trait-level] docs
+ /// contain more details.
+ ///
+ /// [trait-level]: trait.DoubleEndedIterator.html
+ ///
+ /// # Examples
+ ///
+ /// Basic usage:
+ ///
+ /// ```
+ /// let numbers = vec![1, 2, 3];
+ ///
+ /// let mut iter = numbers.iter();
+ ///
+ /// assert_eq!(Some(&1), iter.next());
+ /// assert_eq!(Some(&3), iter.next_back());
+ /// assert_eq!(Some(&2), iter.next_back());
+ /// assert_eq!(None, iter.next());
+ /// assert_eq!(None, iter.next_back());
+ /// ```
+ #[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 iterator that knows its exact length.
+///
+/// Many [`Iterator`]s don't know how many times they will iterate, but some do.
+/// If an iterator knows how many times it can iterate, providing access to
+/// that information can be useful. For example, if you want to iterate
+/// backwards, a good start is to know where the end is.
+///
+/// When implementing an `ExactSizeIterator`, You must also implement
+/// [`Iterator`]. When doing so, the implementation of [`size_hint()`] *must*
+/// return the exact size of the iterator.
+///
+/// [`Iterator`]: trait.Iterator.html
+/// [`size_hint()`]: trait.Iterator.html#method.size_hint
+///
+/// The [`len()`] method has a default implementation, so you usually shouldn't
+/// implement it. However, you may be able to provide a more performant
+/// implementation than the default, so overriding it in this case makes sense.
+///
+/// [`len()`]: #method.len
+///
+/// # Examples
+///
+/// Basic usage:
+///
+/// ```
+/// // a finite range knows exactly how many times it will iterate
+/// let five = 0..5;
+///
+/// assert_eq!(5, five.len());
+/// ```
+///
+/// In the [module level docs][moddocs], we implemented an [`Iterator`],
+/// `Counter`. Let's implement `ExactSizeIterator` for it as well:
+///
+/// [moddocs]: index.html
+///
+/// ```
+/// # struct Counter {
+/// # count: usize,
+/// # }
+/// # impl Counter {
+/// # fn new() -> Counter {
+/// # Counter { count: 0 }
+/// # }
+/// # }
+/// # impl Iterator for Counter {
+/// # type Item = usize;
+/// # fn next(&mut self) -> Option<usize> {
+/// # self.count += 1;
+/// # if self.count < 6 {
+/// # Some(self.count)
+/// # } else {
+/// # None
+/// # }
+/// # }
+/// # }
+/// impl ExactSizeIterator for Counter {
+/// // We already have the number of iterations, so we can use it directly.
+/// fn len(&self) -> usize {
+/// self.count
+/// }
+/// }
+///
+/// // And now we can use it!
+///
+/// let counter = Counter::new();
+///
+/// assert_eq!(0, counter.len());
+/// ```
+#[stable(feature = "rust1", since = "1.0.0")]
+pub trait ExactSizeIterator: Iterator {
+ #[inline]
+ #[stable(feature = "rust1", since = "1.0.0")]
+ /// Returns the exact number of times the iterator will iterate.
+ ///
+ /// This method has a default implementation, so you usually should not
+ /// implement it directly. However, if you can provide a more efficient
+ /// implementation, you can do so. See the [trait-level] docs for an
+ /// example.
+ ///
+ /// This function has the same safety guarantees as the [`size_hint()`]
+ /// function.
+ ///
+ /// [trait-level]: trait.ExactSizeIterator.html
+ /// [`size_hint()`]: trait.Iterator.html#method.size_hint
+ ///
+ /// # Examples
+ ///
+ /// Basic usage:
+ ///
+ /// ```
+ /// // a finite range knows exactly how many times it will iterate
+ /// let five = 0..5;
+ ///
+ /// assert_eq!(5, five.len());
+ /// ```
+ 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 {}
+
generated by cgit v1.2.3 (git 2.25.1) at 2026-04-24 01:28:39 +0000