Struct std::iter::Unfold

pub struct Unfold<St, F> {
    pub state: St,
    // some fields omitted
}

Unstable

An iterator that passes mutable state to a closure and yields the result.

Examples

An iterator that yields sequential Fibonacci numbers, and stops on overflow.

#![feature(core)] fn main() { use std::iter::Unfold; // This iterator will yield up to the last Fibonacci number before the max // value of `u32`. You can simply change `u32` to `u64` in this line if // you want higher values than that. let mut fibonacci = Unfold::new((Some(0u32), Some(1u32)), |&mut (ref mut x2, ref mut x1)| { // Attempt to get the next Fibonacci number // `x1` will be `None` if previously overflowed. let next = match (*x2, *x1) { (Some(x2), Some(x1)) => x2.checked_add(x1), _ => None, }; // Shift left: ret <- x2 <- x1 <- next let ret = *x2; *x2 = *x1; *x1 = next; ret }); for i in fibonacci { println!("{}", i); } }

#![feature(core)]
use std::iter::Unfold;

// This iterator will yield up to the last Fibonacci number before the max
// value of `u32`. You can simply change `u32` to `u64` in this line if
// you want higher values than that.
let mut fibonacci = Unfold::new((Some(0u32), Some(1u32)),
                                |&mut (ref mut x2, ref mut x1)| {
    // Attempt to get the next Fibonacci number
    // `x1` will be `None` if previously overflowed.
    let next = match (*x2, *x1) {
        (Some(x2), Some(x1)) => x2.checked_add(x1),
        _ => None,
    };

    // Shift left: ret <- x2 <- x1 <- next
    let ret = *x2;
    *x2 = *x1;
    *x1 = next;

    ret
});

for i in fibonacci {
    println!("{}", i);
}

Fields

state

Unstable Internal state that will be passed to the closure on the next iteration

Methods

impl<A, St, F> Unfold<St, F> where F: FnMut(&mut St) -> Option<A>

fn new(initial_state: St, f: F) -> Unfold<St, F>

Unstable

Creates a new iterator with the specified closure as the "iterator function" and an initial state to eventually pass to the closure

Trait Implementations

impl<A, St, F> Iterator for Unfold<St, F> where F: FnMut(&mut St) -> Option<A>

type Item = A

fn next(&mut self) -> Option<A>

fn size_hint(&self) -> (usize, Option<usize>)

fn count(self) -> usize

fn last(self) -> Option<Self::Item>

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

fn chain<U>(self, other: U) -> Chain<Self, U::IntoIter> where U: IntoIterator<Item=Self::Item>

fn zip<U>(self, other: U) -> Zip<Self, U::IntoIter> where U: IntoIterator

fn map<B, F>(self, f: F) -> Map<Self, F> where F: FnMut(Self::Item) -> B

fn filter<P>(self, predicate: P) -> Filter<Self, P> where P: FnMut(&Self::Item) -> bool

fn filter_map<B, F>(self, f: F) -> FilterMap<Self, F> where F: FnMut(Self::Item) -> Option<B>

fn enumerate(self) -> Enumerate<Self>

fn peekable(self) -> Peekable<Self>

fn skip_while<P>(self, predicate: P) -> SkipWhile<Self, P> where P: FnMut(&Self::Item) -> bool

fn take_while<P>(self, predicate: P) -> TakeWhile<Self, P> where P: FnMut(&Self::Item) -> bool

fn skip(self, n: usize) -> Skip<Self>

fn take(self, n: usize) -> Take<Self>

fn scan<St, B, F>(self, initial_state: St, f: F) -> Scan<Self, St, F> where F: FnMut(&mut St, Self::Item) -> Option<B>

fn flat_map<U, F>(self, f: F) -> FlatMap<Self, U, F> where U: IntoIterator, F: FnMut(Self::Item) -> U

fn fuse(self) -> Fuse<Self>

fn inspect<F>(self, f: F) -> Inspect<Self, F> where F: FnMut(&Self::Item) -> ()

fn by_ref(&mut self) -> &mut Self

fn collect<B>(self) -> B where B: FromIterator<Self::Item>

fn partition<B, F>(self, f: F) -> (B, B) where F: FnMut(&Self::Item) -> bool, B: Default + Extend<Self::Item>

fn fold<B, F>(self, init: B, f: F) -> B where F: FnMut(B, Self::Item) -> B

fn all<F>(&mut self, f: F) -> bool where F: FnMut(Self::Item) -> bool

fn any<F>(&mut self, f: F) -> bool where F: FnMut(Self::Item) -> bool

fn find<P>(&mut self, predicate: P) -> Option<Self::Item> where P: FnMut(&Self::Item) -> bool

fn position<P>(&mut self, predicate: P) -> Option<usize> where P: FnMut(Self::Item) -> bool

fn rposition<P>(&mut self, predicate: P) -> Option<usize> where Self: ExactSizeIterator + DoubleEndedIterator, P: FnMut(Self::Item) -> bool

fn max(self) -> Option<Self::Item> where Self::Item: Ord

fn min(self) -> Option<Self::Item> where Self::Item: Ord

fn min_max(self) -> MinMaxResult<Self::Item> where Self::Item: Ord

fn max_by<B, F>(self, f: F) -> Option<Self::Item> where B: Ord, F: FnMut(&Self::Item) -> B

fn min_by<B, F>(self, f: F) -> Option<Self::Item> where B: Ord, F: FnMut(&Self::Item) -> B

fn rev(self) -> Rev<Self> where Self: DoubleEndedIterator

fn unzip<A, B, FromA, FromB>(self) -> (FromA, FromB) where FromA: Default + Extend<A>, FromB: Default + Extend<B>, Self: Iterator<Item=(A, B)>

fn cloned<'a, T>(self) -> Cloned<Self> where T: 'a + Clone, Self: Iterator<Item=&'a T>

fn cycle(self) -> Cycle<Self> where Self: Clone

fn reverse_in_place<'a, T>(&mut self) where Self: Iterator<Item=&'a mut T> + DoubleEndedIterator, T: 'a

fn sum<S = Self::Item>(self) -> S where S: Add<Self::Item, Output=S> + Zero

fn product<P = Self::Item>(self) -> P where P: Mul<Self::Item, Output=P> + One

Derived Implementations

impl<St, F> Clone for Unfold<St, F> where F: Clone + Clone, St: Clone + Clone

fn clone(&self) -> Unfold<St, F>

fn clone_from(&mut self, source: &Self)