Struct std::iter::OnceIterator

struct OnceIterator<T> { ... }

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Iterator that yields a single value

See once for more details.

Methods

impl OnceIterator<T> { ... }

fn next(self: &mut OnceIterator<T>) -> Option<T>

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Returns the next item, if any.
If the iterator has reached the end, it returns Option::none().
See Iterator for more information.
fn next_back(self: &mut OnceIterator<T>) -> Option<T>

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Returns the next item from the back, if any.
If the iterator has reached the beginning, it returns none.
See DoubleEndedIterator for more information.
fn size_hint(self: &OnceIterator<T>) -> Option<usize>

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Returns the number of remaining elements, if available.
See Iterator for more information.

Mixins

impl OnceIterator<T> { ... }

mixin Iterator<OnceIterator<T>, T>
mixin IteratorExt<OnceIterator<T>, T>

fn iter(self: &mut Self) -> &mut Self

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Return self.
Each iterator is itself an iterable object, though only once. This helper function is there so that iterators can be used ergonomically in for loops (which de-sugar to a call to .iter())
See also iter.
fn fuse(self: &mut Self) -> FusedIterator<Self, T>

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Return an iterator that returns Option::none() forever after the first one is returned.
Iterators can validly reset back to returning values after they are exhausted. This method "caps it off" after they are first exhausted.

fn chain<Other>(self: &mut Self, other: &mut Other) -> ChainIterator<Self, Other, T>
Other: Iterator<Other, T>

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Returns an iterator that yields all elements of self and then all elements of other.

Example

let range = (0..2).chain(&(10..12));
assert_eq!(range.size_hint(), Option::some(4usize));

assert_eq!(range.next(), Option::some(0));
assert_eq!(range.next(), Option::some(1));
assert_eq!(range.next(), Option::some(10));
assert_eq!(range.next(), Option::some(11));
assert_eq!(range.next(), Option::none());
Run this example

fn merge_sorted<Other>(self: &mut Self, other: &mut Other) -> MergeIterator<Self, Other, T>
Other: Iterator<Other, T>

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Returns an iterator that merges two sorted iterators into one sorted iterator.
T must implement Comparable. If the two iterators are not sorted, the resulting order is unspecified.
The merge is stable, meaning that the order of equal elements is preserved, with the elements from self coming before the elements from other (and vice-versa if the iterator is reversed/used with next_back).

Example
```
let range = [0, 2, 4].iter().merge_sorted(&[1, 3].iter());
assert_eq!(range.size_hint(), Option::some(5usize));

assert_eq!(range.next(), Option::some(0));
assert_eq!(range.next(), Option::some(1));
assert_eq!(range.next(), Option::some(2));
assert_eq!(range.next(), Option::some(3));
assert_eq!(range.next(), Option::some(4));
assert_eq!(range.next(), Option::none());
Run this example
```

fn skip(self: &mut Self, n: usize) -> SkipIterator<Self, T>

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Returns an iterator that skips first n values.

If the underlying iterator yields fewer than or exactly n values, then the iterator will yield no values.

Example

let range = (0..5).skip(2);
assert_eq!(range.size_hint(), Option::some(3usize));

assert_eq!(range.next(), Option::some(2));
assert_eq!(range.next(), Option::some(3));
assert_eq!(range.next(), Option::some(4));
assert_eq!(range.next(), Option::none());
Run this example

fn step_by(self: &mut Self, n: usize) -> StepByIterator<Self, T>

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Returns an iterator that steps by n values.

First value will always be yielded, then every n-th value.

Example

let range = (0..5).step_by(2);
assert_eq!(range.size_hint(), Option::some(3usize));

assert_eq!(range.next(), Option::some(0));
assert_eq!(range.next(), Option::some(2));
assert_eq!(range.next(), Option::some(4));
assert_eq!(range.next(), Option::none());
Run this example

fn take(self: &mut Self, n: usize) -> TakeIterator<Self, T>

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Returns an iterator that yields at most n elements.

Example

let range = (0..5).take(2);
assert_eq!(range.size_hint(), Option::some(2usize));

assert_eq!(range.next(), Option::some(0));
assert_eq!(range.next(), Option::some(1));
assert_eq!(range.next(), Option::none());
Run this example

fn enumerate(self: &mut Self) -> EnumerateIterator<Self, T>

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Returns an iterator that attaches a sequence number of each item.

Example

let range = (10..15).enumerate();
assert_eq!(range.size_hint(), Option::some(5usize));

assert_eq!(range.next(), Option::some((0usize, 10)));
assert_eq!(range.next(), Option::some((1usize, 11)));
assert_eq!(range.next(), Option::some((2usize, 12)));
assert_eq!(range.next(), Option::some((3usize, 13)));
assert_eq!(range.next(), Option::some((4usize, 14)));
assert_eq!(range.next(), Option::none());
Run this example

fn last(self: &mut Self) -> Option<T>

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Returns the last value of the iterator.
This method always exhausts the iterator. For iterators that implement DoubleEndedIterator, it may be more efficient to use next_back.

Example
```
let last = (0..5).last();

assert_eq!(last, Option::some(4));
Run this example
```
fn nth(self: &mut Self, n: usize) -> Option<T>

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Returns the n-th value of the iterator.

Example
```
let nth = (10..100).nth(2);

assert_eq!(nth, Option::some(12));
Run this example
```
fn count(self: &mut Self) -> usize

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Counts the number of elements in this iterator.

Example
```
let count = (100..105).count();

assert_eq!(count, 5);
Run this example
```
fn inspect<F>(it: &mut Self, func: F) -> InspectIterator<Self, F, T>
F: Fn(T)

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Inspects each element of the iterator.
Presented chain of iterator combinators, inspect can be used to execute a callback on every element of an iterator. This is useful for debugging.
The elements are passed through unmodified.

Example
```
let last = (0..3)
    .iter()
    .inspect(|i: i32| { println!("I see {}", i) })
    .last();

println!("Last: {}", last);

// Prints:
// I see 0
// I see 1
// I see 2
// Last: 2
Run this example
```

fn take_while<F>(iter: &mut Self, fun: F) -> TakeWhileIterator<Self, F, T>
F: Fn(T) -> bool

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Returns an iterator that yields the elements while a predicate is true.

Example

let range = (0..5).take_while(|x: i32| -> bool { x < 3 });
assert_eq!(range.size_hint(), Option::none());

assert_eq!(range.next(), Option::some(0));
assert_eq!(range.next(), Option::some(1));
assert_eq!(range.next(), Option::some(2));
assert_eq!(range.next(), Option::none());
Run this example

fn skip_while<F>(iter: &mut Self, fun: F) -> SkipWhileIterator<Self, F, T>
F: Fn(T) -> bool

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Returns an iterator that skips the elements while a predicate is true.

Example

let range = (0..5).skip_while(|x: i32| -> bool { x < 3 });
assert_eq!(range.size_hint(), Option::none());

assert_eq!(range.next(), Option::some(3));
assert_eq!(range.next(), Option::some(4));
assert_eq!(range.next(), Option::none());
Run this example

fn map<U, F>(iter: &mut Self, fun: F) -> MapIterator<Self, F, T, U>
F: Fn(T) -> U

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Returns an iterator that transforms the elements of this iterator.

Example

let range = (0..5).map(|x: i32| -> i32 { x * 2 });
assert_eq!(range.size_hint(), Option::some(5usize));

assert_eq!(range.next(), Option::some(0));
assert_eq!(range.next(), Option::some(2));
assert_eq!(range.next(), Option::some(4));
assert_eq!(range.next(), Option::some(6));
assert_eq!(range.next(), Option::some(8));
assert_eq!(range.next(), Option::none());
Run this example

fn foreach<F>(iter: &mut Self, fun: F)
F: Fn(T)

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Executes a function on each element of this iterator.
For readability, it is usually better to use the for loop, but foreach can be useful in cases where a function allocates memory which can be then freed using a defer expression.

Example
```
use std::fmt::format;

(0..5)
    .iter()
    .foreach(|x: i32| {
        let f = format!("{}", x).unwrap();
        defer f.free();

        println!("{}", f[..]);
    });
Run this example
```

fn filter<F>(iter: &mut Self, fun: F) -> FilterIterator<Self, F, T>
F: Fn(T) -> bool

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Returns an iterator that yields the elements of this iterator that match a predicate.

Example

let range = (0..5).filter(|x: i32| -> bool { x % 2 == 0 });
assert_eq!(range.size_hint(), Option::none());

assert_eq!(range.next(), Option::some(0));
assert_eq!(range.next(), Option::some(2));
assert_eq!(range.next(), Option::some(4));
assert_eq!(range.next(), Option::none());
Run this example

fn find<F>(iter: &mut Self, fun: F) -> Option<T>
F: Fn(T) -> bool

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Returns the first item matching the predicate.

If there is no item matching the predicate, returns none.

Example

let a = (1..10).find(|x: i32| -> bool { x * x >= 50 });
let b = (1..10).find(|x: i32| -> bool { x * x >= 1000 });

assert_eq!(a, Option::some(8));
assert_eq!(b, Option::none());
Run this example

fn find_index<F>(iter: &mut Self, fun: F) -> Option<usize>
F: Fn(T) -> bool

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Returns the index of the first item matching the predicate.
If there is no item matching the predicate, returns none.

Example
```
let arr = [1, 2, 3, 1337, 5, 6];

let idx = arr
    .iter()
    .find_index(|x: i32| -> bool { x > 100 })
    .unwrap();

println!("First number larger than 100: {}", arr[idx]);
Run this example
```

fn filter_map<U, F>(iter: &mut Self, fun: F) -> FilterMapIterator<Self, F, T, U>
F: Fn(T) -> Option<U>

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Transforms and filters the iterator at the same time.

Function f is called on each element of this iterator. If it returns Option::some(...), that element is yielded. If it returns Option::none(), the element is skipped.

Example

let range = (0..6)
    .iter()
    .filter_map(|x: i32| -> Option<i32> {
        if x % 2 == 1 {
            Option::some(x * 100)
        } else {
            Option::none()
        }
    });

assert_eq!(range.next(), Option::some(100));
assert_eq!(range.next(), Option::some(300));
assert_eq!(range.next(), Option::some(500));
Run this example

fn chunks(self: &mut Self, chunk_size: usize) -> ChunksIterator<Self, T>

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Returns an iterator of chunks of size chunk_size.
If the iterator is not divisible by chunk_size, the last chunk will be smaller. Panics if chunk_size is 0.

Example
```
// Prints:
// [ 0 1 2 ]
// [ 3 4 5 ]
// [ 6 ]
for chunk in (0..7).chunks(3) {
    print!("[ ");
    for v in chunk {
        print!("{} ", v);
    }
    println!("]");
}
Run this example
```

fn reduce<U, F>(iter: &mut Self, initial: U, func: F) -> U
F: Fn(U, T) -> U

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Reduces the iterator into a single value.

Equivalent to:

let value = initial;
for element in iter {
    value = func(value, element);
}

Example

let sum = (0..5)
    .iter()
    .reduce(0, |acc: i32, x: i32| -> i32 { acc + x });

println!("{}", sum); // Prints: 10
Run this example

fn sum(iter: &mut Self) -> T

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Sums all the values in the iterator.
T must satisfy Numeric protocol.

Example
```
let sum = (0..5).sum();

assert_eq!(sum, 10);
Run this example
```
fn min(iter: &mut Self) -> Option<T>

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Returns the minimum value of the iterator.
T must satisfy Comparable protocol.

Example
```
let min = [1, -5, 10, 200].iter().min();

assert_eq!(min, Option::some(-5));
Run this example
```
fn max(iter: &mut Self) -> Option<T>

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Returns the maximum value of the iterator.
T must satisfy Comparable protocol.

Example
```
let max = [1, -5, 10, 200].iter().max();

assert_eq!(max, Option::some(200));
Run this example
```
fn all<F>(iter: &mut Self, fun: F) -> bool
F: Fn(T) -> bool

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Returns true if all elements of the iterator match a predicate, false otherwise.
If iterator produces no values, true is returned.

Example
```
let t1 = [1, -5, 10, 200].iter().all(|x: i32| -> bool { x > 0 });
let t2 = [1, -5, 10, 200].iter().all(|x: i32| -> bool { x < 1000 });

assert!(!t1);
assert!(t2);
Run this example
```
fn any<F>(iter: &mut Self, fun: F) -> bool
F: Fn(T) -> bool

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Returns true if any element of the iterator matches a predicate, false otherwise.
If iterator produces no values, false is returned.

Example
```
let t1 = [1, -5, 10, 200].iter().any(|x: i32| -> bool { x > 1000 });
let t2 = [1, -5, 10, 200].iter().any(|x: i32| -> bool { x < 0 });

assert!(!t1);
assert!(t2);
Run this example
```

fn to_vector(self: &mut Self) -> Vector<T>

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Collects the values of the iterator into a vector.

Example

let range = (0..5).to_vector();
defer range.free();

assert_eq!(range.len(), 5);
assert_eq!(range[..], &[0, 1, 2, 3, 4]);
Run this example

fn fill_slice(self: &mut Self, slice: &mut [T]) -> usize

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Fills the slice with the values of the iterator.
If the number of elements in the iterator is greater than the length of the slice, the remaining values in the iterator are not consumed.
If the number of elements in the iterator is less than the length of the slice, the remainder of the slice is untouched.

Example
```
let buf: [i32; 5];
(0..5).fill_slice(buf[..]);

assert_eq!(buf[..], &[0, 1, 2, 3, 4]);
Run this example
```
fn peekable(self: &mut Self) -> PeekableIterator<Self, T>

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Returns a "peekable" iterator.
Peekable iterators have an additional method, peek, which is similar to next, but it does not consume the value, so a subsequent call to next will return the same value.

fn group_by<F, K>(self: &mut Self, func: F) -> GroupByIterator<Self, F, T, K>
F: Fn(T) -> K

K: Equatable<K>

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Returns an iterator of groups grouped by a key.

Requires that the items of the iterator that have the same key are contiguous (e.g. the values are sorted by key).

Example

fn divide_by_three(x: i32) -> i32 { x / 3 }

for group in (0..10).group_by(divide_by_three) {
    print!("{}:", group.key);
    for value in group {
        print!(" {}", value);
    }
    println!("");
}

// Prints:
// 0: 0 1 2
// 1: 3 4 5
// 2: 6 7 8
// 3: 9
Run this example

fn zip<Other>(self: &mut Self, other: &mut Other) -> ZipIterator<Self, Other, T, iterator_yield_t<Other>>

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Combines two iterators, returning an iterator of pairs.

Example

let iter = (0..5).zip(&(10..15));

assert_eq!(iter.size_hint(), Option::some(5usize));

assert_eq!(iter.next(), Option::some((0, 10)));
assert_eq!(iter.next(), Option::some((1, 11)));
assert_eq!(iter.next(), Option::some((2, 12)));
assert_eq!(iter.next(), Option::some((3, 13)));
assert_eq!(iter.next(), Option::some((4, 14)));
assert_eq!(iter.next(), Option::none());
Run this example

fn flatten(self: &mut Self) -> FlattenIterator<Self, T, iterable_yield_t<T>>

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Flattens an iterator over iterable types into a single iterator.

Example

let iter = ["Hello", " ", "World"].iter().flatten();

let v = iter.to_vector();
defer v.free();

assert_eq!(v[..], &['H', 'e', 'l', 'l', 'o', ' ', 'W', 'o', 'r', 'l', 'd']);
Run this example

Struct std::iter::OnceIterator

struct OnceIterator<T> { ... }

Methods

impl OnceIterator<T> { ... }

fn next(self: &mut OnceIterator<T>) -> Option<T>

fn next_back(self: &mut OnceIterator<T>) -> Option<T>

fn size_hint(self: &OnceIterator<T>) -> Option<usize>

Mixins

impl OnceIterator<T> { ... }

mixin Iterator<OnceIterator<T>, T>

mixin IteratorExt<OnceIterator<T>, T>

fn iter(self: &mut Self) -> &mut Self

fn fuse(self: &mut Self) -> FusedIterator<Self, T>

fn chain<Other>(self: &mut Self, other: &mut Other) -> ChainIterator<Self, Other, T> Other: Iterator<Other, T>

Example

fn merge_sorted<Other>(self: &mut Self, other: &mut Other) -> MergeIterator<Self, Other, T> Other: Iterator<Other, T>

Example

fn skip(self: &mut Self, n: usize) -> SkipIterator<Self, T>

Example

fn step_by(self: &mut Self, n: usize) -> StepByIterator<Self, T>

Example

fn take(self: &mut Self, n: usize) -> TakeIterator<Self, T>

Example

fn enumerate(self: &mut Self) -> EnumerateIterator<Self, T>

Example

fn last(self: &mut Self) -> Option<T>

Example

fn nth(self: &mut Self, n: usize) -> Option<T>

Example

fn count(self: &mut Self) -> usize

Example

fn inspect<F>(it: &mut Self, func: F) -> InspectIterator<Self, F, T> F: Fn(T)

Example

fn take_while<F>(iter: &mut Self, fun: F) -> TakeWhileIterator<Self, F, T> F: Fn(T) -> bool

Example

fn skip_while<F>(iter: &mut Self, fun: F) -> SkipWhileIterator<Self, F, T> F: Fn(T) -> bool

Example

fn map<U, F>(iter: &mut Self, fun: F) -> MapIterator<Self, F, T, U> F: Fn(T) -> U

Example

fn foreach<F>(iter: &mut Self, fun: F) F: Fn(T)

Example

fn filter<F>(iter: &mut Self, fun: F) -> FilterIterator<Self, F, T> F: Fn(T) -> bool

Example

fn find<F>(iter: &mut Self, fun: F) -> Option<T> F: Fn(T) -> bool

Example

fn find_index<F>(iter: &mut Self, fun: F) -> Option<usize> F: Fn(T) -> bool

Example

fn filter_map<U, F>(iter: &mut Self, fun: F) -> FilterMapIterator<Self, F, T, U> F: Fn(T) -> Option<U>

Example

fn chunks(self: &mut Self, chunk_size: usize) -> ChunksIterator<Self, T>

Example

fn reduce<U, F>(iter: &mut Self, initial: U, func: F) -> U F: Fn(U, T) -> U

Example

fn sum(iter: &mut Self) -> T

Example

fn min(iter: &mut Self) -> Option<T>

Example

fn max(iter: &mut Self) -> Option<T>

Example

fn all<F>(iter: &mut Self, fun: F) -> bool F: Fn(T) -> bool

Example

fn any<F>(iter: &mut Self, fun: F) -> bool F: Fn(T) -> bool

Example

fn to_vector(self: &mut Self) -> Vector<T>

Example

fn fill_slice(self: &mut Self, slice: &mut [T]) -> usize

Example

fn peekable(self: &mut Self) -> PeekableIterator<Self, T>

fn group_by<F, K>(self: &mut Self, func: F) -> GroupByIterator<Self, F, T, K> F: Fn(T) -> K K: Equatable<K>

Example

fn zip<Other>(self: &mut Self, other: &mut Other) -> ZipIterator<Self, Other, T, iterator_yield_t<Other>>

Example

fn flatten(self: &mut Self) -> FlattenIterator<Self, T, iterable_yield_t<T>>

Example

fn chain<Other>(self: &mut Self, other: &mut Other) -> ChainIterator<Self, Other, T>
Other: Iterator<Other, T>

fn merge_sorted<Other>(self: &mut Self, other: &mut Other) -> MergeIterator<Self, Other, T>
Other: Iterator<Other, T>

fn inspect<F>(it: &mut Self, func: F) -> InspectIterator<Self, F, T>
F: Fn(T)

fn take_while<F>(iter: &mut Self, fun: F) -> TakeWhileIterator<Self, F, T>
F: Fn(T) -> bool

fn skip_while<F>(iter: &mut Self, fun: F) -> SkipWhileIterator<Self, F, T>
F: Fn(T) -> bool

fn map<U, F>(iter: &mut Self, fun: F) -> MapIterator<Self, F, T, U>
F: Fn(T) -> U

fn foreach<F>(iter: &mut Self, fun: F)
F: Fn(T)

fn filter<F>(iter: &mut Self, fun: F) -> FilterIterator<Self, F, T>
F: Fn(T) -> bool

fn find<F>(iter: &mut Self, fun: F) -> Option<T>
F: Fn(T) -> bool

fn find_index<F>(iter: &mut Self, fun: F) -> Option<usize>
F: Fn(T) -> bool

fn filter_map<U, F>(iter: &mut Self, fun: F) -> FilterMapIterator<Self, F, T, U>
F: Fn(T) -> Option<U>

fn reduce<U, F>(iter: &mut Self, initial: U, func: F) -> U
F: Fn(U, T) -> U

fn all<F>(iter: &mut Self, fun: F) -> bool
F: Fn(T) -> bool

fn any<F>(iter: &mut Self, fun: F) -> bool
F: Fn(T) -> bool

fn group_by<F, K>(self: &mut Self, func: F) -> GroupByIterator<Self, F, T, K>
F: Fn(T) -> K

K: Equatable<K>