Trait std::iter::Iterator
pub trait Iterator<A> { fn next(&mut self) -> Option<A>; fn size_hint(&self) -> (uint, Option<uint>) { ... } fn chain<U: Iterator<A>>(self, other: U) -> Chain<Self, U> { ... } fn zip<B, U: Iterator<B>>(self, other: U) -> Zip<Self, U> { ... } fn map<'r, B>(self, f: 'r |A| -> B) -> Map<'r, A, B, Self> { ... } fn filter<'r>(self, predicate: 'r |&A| -> bool) -> Filter<'r, A, Self> { ... } fn filter_map<'r, B>(self, f: 'r |A| -> Option<B>) -> FilterMap<'r, A, B, Self> { ... } fn enumerate(self) -> Enumerate<Self> { ... } fn peekable(self) -> Peekable<A, Self> { ... } fn skip_while<'r>(self, predicate: 'r |&A| -> bool) -> SkipWhile<'r, A, Self> { ... } fn take_while<'r>(self, predicate: 'r |&A| -> bool) -> TakeWhile<'r, A, Self> { ... } fn skip(self, n: uint) -> Skip<Self> { ... } fn take(self, n: uint) -> Take<Self> { ... } fn scan<'r, St, B>(self, initial_state: St, f: 'r |&mut St, A| -> Option<B>) -> Scan<'r, A, B, Self, St> { ... } fn flat_map<'r, B, U: Iterator<B>>(self, f: 'r |A| -> U) -> FlatMap<'r, A, Self, U> { ... } fn fuse(self) -> Fuse<Self> { ... } fn inspect<'r>(self, f: 'r |&A|) -> Inspect<'r, A, Self> { ... } fn by_ref<'r>(&'r mut self) -> ByRef<'r, Self> { ... } fn advance(&mut self, f: |A| -> bool) -> bool { ... } fn collect<B: FromIterator<A>>(&mut self) -> B { ... } fn nth(&mut self, n: uint) -> Option<A> { ... } fn last(&mut self) -> Option<A> { ... } fn fold<B>(&mut self, init: B, f: |B, A| -> B) -> B { ... } fn len(&mut self) -> uint { ... } fn all(&mut self, f: |A| -> bool) -> bool { ... } fn any(&mut self, f: |A| -> bool) -> bool { ... } fn find(&mut self, predicate: |&A| -> bool) -> Option<A> { ... } fn position(&mut self, predicate: |A| -> bool) -> Option<uint> { ... } fn count(&mut self, predicate: |A| -> bool) -> uint { ... } fn max_by<B: TotalOrd>(&mut self, f: |&A| -> B) -> Option<A> { ... } fn min_by<B: TotalOrd>(&mut self, f: |&A| -> B) -> Option<A> { ... } }
An interface for dealing with "external iterators". These types of iterators can be resumed at any time as all state is stored internally as opposed to being located on the call stack.
The Iterator protocol states that an iterator yields a (potentially-empty,
potentially-infinite) sequence of values, and returns None
to signal that
it's finished. The Iterator protocol does not define behavior after None
is returned. A concrete Iterator implementation may choose to behave however
it wishes, either by returning None
infinitely, or by doing something
else.
Required Methods
fn next(&mut self) -> Option<A>
Advance the iterator and return the next value. Return None
when the end is reached.
Provided Methods
fn size_hint(&self) -> (uint, Option<uint>)
Return a lower bound and upper bound on the remaining length of the iterator.
The common use case for the estimate is pre-allocating space to store the results.
fn chain<U: Iterator<A>>(self, other: U) -> Chain<Self, U>
Chain this iterator with another, returning a new iterator which will finish iterating over the current iterator, and then it will iterate over the other specified iterator.
Example
let a = [0]; let b = [1]; let mut it = a.iter().chain(b.iter()); assert_eq!(it.next().unwrap(), &0); assert_eq!(it.next().unwrap(), &1); assert!(it.next().is_none());
fn zip<B, U: Iterator<B>>(self, other: U) -> Zip<Self, U>
Creates an iterator which iterates over both this and the specified iterators simultaneously, yielding the two elements as pairs. When either iterator returns None, all further invocations of next() will return None.
Example
let a = [0]; let b = [1]; let mut it = a.iter().zip(b.iter()); assert_eq!(it.next().unwrap(), (&0, &1)); assert!(it.next().is_none());
fn map<'r, B>(self, f: 'r |A| -> B) -> Map<'r, A, B, Self>
Creates a new iterator which will apply the specified function to each element returned by the first, yielding the mapped element instead.
Example
let a = [1, 2]; let mut it = a.iter().map(|&x| 2 * x); assert_eq!(it.next().unwrap(), 2); assert_eq!(it.next().unwrap(), 4); assert!(it.next().is_none());
fn filter<'r>(self, predicate: 'r |&A| -> bool) -> Filter<'r, A, Self>
Creates an iterator which applies the predicate to each element returned
by this iterator. Only elements which have the predicate evaluate to
true
will be yielded.
Example
let a = [1, 2]; let mut it = a.iter().filter(|&x| *x > 1); assert_eq!(it.next().unwrap(), &2); assert!(it.next().is_none());
fn filter_map<'r, B>(self, f: 'r |A| -> Option<B>) -> FilterMap<'r, A, B, Self>
Creates an iterator which both filters and maps elements. If the specified function returns None, the element is skipped. Otherwise the option is unwrapped and the new value is yielded.
Example
let a = [1, 2]; let mut it = a.iter().filter_map(|&x| if x > 1 {Some(2 * x)} else {None}); assert_eq!(it.next().unwrap(), 4); assert!(it.next().is_none());
fn enumerate(self) -> Enumerate<Self>
Creates an iterator which yields a pair of the value returned by this iterator plus the current index of iteration.
Example
let a = [100, 200]; let mut it = a.iter().enumerate(); assert_eq!(it.next().unwrap(), (0, &100)); assert_eq!(it.next().unwrap(), (1, &200)); assert!(it.next().is_none());
fn peekable(self) -> Peekable<A, Self>
Creates an iterator that has a .peek()
method
that returns an optional reference to the next element.
Example
let xs = [100, 200, 300]; let mut it = xs.iter().map(|x| *x).peekable(); assert_eq!(it.peek().unwrap(), &100); assert_eq!(it.next().unwrap(), 100); assert_eq!(it.next().unwrap(), 200); assert_eq!(it.peek().unwrap(), &300); assert_eq!(it.peek().unwrap(), &300); assert_eq!(it.next().unwrap(), 300); assert!(it.peek().is_none()); assert!(it.next().is_none());
fn skip_while<'r>(self, predicate: 'r |&A| -> bool) -> SkipWhile<'r, A, Self>
Creates an iterator which invokes the predicate on elements until it returns false. Once the predicate returns false, all further elements are yielded.
Example
let a = [1, 2, 3, 2, 1]; let mut it = a.iter().skip_while(|&a| *a < 3); assert_eq!(it.next().unwrap(), &3); assert_eq!(it.next().unwrap(), &2); assert_eq!(it.next().unwrap(), &1); assert!(it.next().is_none());
fn take_while<'r>(self, predicate: 'r |&A| -> bool) -> TakeWhile<'r, A, Self>
Creates an iterator which yields elements so long as the predicate returns true. After the predicate returns false for the first time, no further elements will be yielded.
Example
let a = [1, 2, 3, 2, 1]; let mut it = a.iter().take_while(|&a| *a < 3); assert_eq!(it.next().unwrap(), &1); assert_eq!(it.next().unwrap(), &2); assert!(it.next().is_none());
fn skip(self, n: uint) -> Skip<Self>
Creates an iterator which skips the first n
elements of this iterator,
and then it yields all further items.
Example
let a = [1, 2, 3, 4, 5]; let mut it = a.iter().skip(3); assert_eq!(it.next().unwrap(), &4); assert_eq!(it.next().unwrap(), &5); assert!(it.next().is_none());
fn take(self, n: uint) -> Take<Self>
Creates an iterator which yields the first n
elements of this
iterator, and then it will always return None.
Example
let a = [1, 2, 3, 4, 5]; let mut it = a.iter().take(3); assert_eq!(it.next().unwrap(), &1); assert_eq!(it.next().unwrap(), &2); assert_eq!(it.next().unwrap(), &3); assert!(it.next().is_none());
fn scan<'r, St, B>(self, initial_state: St, f: 'r |&mut St, A| -> Option<B>) -> Scan<'r, A, B, Self, St>
Creates a new iterator which behaves in a similar fashion to foldl. There is a state which is passed between each iteration and can be mutated as necessary. The yielded values from the closure are yielded from the Scan instance when not None.
Example
let a = [1, 2, 3, 4, 5]; let mut it = a.iter().scan(1, |fac, &x| { *fac = *fac * x; Some(*fac) }); assert_eq!(it.next().unwrap(), 1); assert_eq!(it.next().unwrap(), 2); assert_eq!(it.next().unwrap(), 6); assert_eq!(it.next().unwrap(), 24); assert_eq!(it.next().unwrap(), 120); assert!(it.next().is_none());
fn flat_map<'r, B, U: Iterator<B>>(self, f: 'r |A| -> U) -> FlatMap<'r, A, Self, U>
Creates an iterator that maps each element to an iterator, and yields the elements of the produced iterators
Example
use std::iter::count; let xs = [2u, 3]; let ys = [0u, 1, 0, 1, 2]; let mut it = xs.iter().flat_map(|&x| count(0u, 1).take(x)); // Check that `it` has the same elements as `ys` let mut i = 0; for x in it { assert_eq!(x, ys[i]); i += 1; }
fn fuse(self) -> Fuse<Self>
Creates an iterator that yields None
forever after the underlying
iterator yields None
. Random-access iterator behavior is not
affected, only single and double-ended iterator behavior.
Example
fn process<U: Iterator<int>>(it: U) -> int { let mut it = it.fuse(); let mut sum = 0; for x in it { if x > 5 { continue; } sum += x; } // did we exhaust the iterator? if it.next().is_none() { sum += 1000; } sum } let x = ~[1,2,3,7,8,9]; assert_eq!(process(x.move_iter()), 1006);
fn inspect<'r>(self, f: 'r |&A|) -> Inspect<'r, A, Self>
Creates an iterator that calls a function with a reference to each element before yielding it. This is often useful for debugging an iterator pipeline.
Example
use std::iter::AdditiveIterator; let xs = [1u, 4, 2, 3, 8, 9, 6]; let sum = xs.iter() .map(|&x| x) .inspect(|&x| println!("filtering {}", x)) .filter(|&x| x % 2 == 0) .inspect(|&x| println!("{} made it through", x)) .sum(); println!("{}", sum);
fn by_ref<'r>(&'r mut self) -> ByRef<'r, Self>
Creates a wrapper around a mutable reference to the iterator.
This is useful to allow applying iterator adaptors while still retaining ownership of the original iterator value.
Example
let mut xs = range(0, 10); // sum the first five values let partial_sum = xs.by_ref().take(5).fold(0, |a, b| a + b); assert!(partial_sum == 10); // xs.next() is now `5` assert!(xs.next() == Some(5));
fn advance(&mut self, f: |A| -> bool) -> bool
Apply a function to each element, or stop iterating if the
function returns false
.
Example
range(0, 5).advance(|x| {print!("{} ", x); true});
fn collect<B: FromIterator<A>>(&mut self) -> B
Loops through the entire iterator, collecting all of the elements into
a container implementing FromIterator
.
Example
let a = [1, 2, 3, 4, 5]; let b: ~[int] = a.iter().map(|&x| x).collect(); assert!(a == b);
fn nth(&mut self, n: uint) -> Option<A>
Loops through n
iterations, returning the n
th element of the
iterator.
Example
let a = [1, 2, 3, 4, 5]; let mut it = a.iter(); assert!(it.nth(2).unwrap() == &3); assert!(it.nth(2) == None);
fn last(&mut self) -> Option<A>
Loops through the entire iterator, returning the last element of the iterator.
Example
let a = [1, 2, 3, 4, 5]; assert!(a.iter().last().unwrap() == &5);
fn fold<B>(&mut self, init: B, f: |B, A| -> B) -> B
Performs a fold operation over the entire iterator, returning the eventual state at the end of the iteration.
Example
let a = [1, 2, 3, 4, 5]; assert!(a.iter().fold(0, |a, &b| a + b) == 15);
fn len(&mut self) -> uint
Counts the number of elements in this iterator.
Example
let a = [1, 2, 3, 4, 5]; let mut it = a.iter(); assert!(it.len() == 5); assert!(it.len() == 0);
fn all(&mut self, f: |A| -> bool) -> bool
Tests whether the predicate holds true for all elements in the iterator.
Example
let a = [1, 2, 3, 4, 5]; assert!(a.iter().all(|x| *x > 0)); assert!(!a.iter().all(|x| *x > 2));
fn any(&mut self, f: |A| -> bool) -> bool
Tests whether any element of an iterator satisfies the specified predicate.
Example
let a = [1, 2, 3, 4, 5]; let mut it = a.iter(); assert!(it.any(|x| *x == 3)); assert!(!it.any(|x| *x == 3));
fn find(&mut self, predicate: |&A| -> bool) -> Option<A>
Return the first element satisfying the specified predicate
fn position(&mut self, predicate: |A| -> bool) -> Option<uint>
Return the index of the first element satisfying the specified predicate
fn count(&mut self, predicate: |A| -> bool) -> uint
Count the number of elements satisfying the specified predicate
fn max_by<B: TotalOrd>(&mut self, f: |&A| -> B) -> Option<A>
Return the element that gives the maximum value from the specified function.
Example
let xs = [-3i, 0, 1, 5, -10]; assert_eq!(*xs.iter().max_by(|x| x.abs()).unwrap(), -10);
fn min_by<B: TotalOrd>(&mut self, f: |&A| -> B) -> Option<A>
Return the element that gives the minimum value from the specified function.
Example
let xs = [-3i, 0, 1, 5, -10]; assert_eq!(*xs.iter().min_by(|x| x.abs()).unwrap(), 0);
Implementors
BlockedTasks
Parser<'a>
IncomingConnections<'a, A>
Chars<'r, T>
Lines<'r, T>
Directories
Bytes<'r, R>
CChars<'a>
Messages<'a, T>
Item<A>
Repeat<A>
RangeStepInclusive<A>
RangeStep<A>
RangeInclusive<A>
Range<A>
Counter<A>
Unfold<'a, A, St>
Inspect<'a, A, T>
Fuse<T>
FlatMap<'a, A, T, U>
Scan<'a, A, B, T, St>
Take<T>
Skip<T>
TakeWhile<'a, A, T>
SkipWhile<'a, A, T>
Peekable<A, T>
Enumerate<T>
FilterMap<'a, A, B, T>
Filter<'a, A, T>
Map<'a, A, B, T>
Zip<T, U>
Chain<T, U>
Cycle<T>
ByRef<'a, T>
Rev<T>
UTF16Items<'a>
Normalizations<'a>
StrSplits<'a>
MatchIndices<'a>
CharSplitsN<'a, Sep>
CharSplits<'a, Sep>
CharOffsets<'a>
Chars<'a>
MoveItems<T>
MoveItems<T>
MutChunks<'a, T>
MutSplits<'a, T>
MutItems<'a, T>
Items<'a, T>
Chunks<'a, T>
Windows<'a, T>
Permutations<T>
ElementSwaps
RevSplits<'a, T>
Splits<'a, T>