Struct itertools::Unfold [−] [src]

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

Unfold is a general iterator builder: it has a mutable state value, and a closure with access to the state that produces the next value.

This more or less equivalent to a regular struct with an Iterator implementation, and is useful for one-off iterators.

// an iterator that yields sequential Fibonacci numbers,
// and stops at the maximum representable value.

use itertools::Unfold;

let mut fibonacci = Unfold::new((1_u32, 1_u32), |state| {
    let (ref mut x1, ref mut x2) = *state;

    // Attempt to get the next Fibonacci number
    let next = x1.saturating_add(*x2);

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

    // If addition has saturated at the maximum, we are finished
    if ret == *x1 && ret > 1 {
        return None;
    }

    Some(ret)
});

itertools::assert_equal(fibonacci.by_ref().take(8),
                        vec![1, 1, 2, 3, 5, 8, 13, 21]);
assert_eq!(fibonacci.last(), Some(2_971_215_073))

Fields

state

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>[−]

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>)

1.0.0fn count(self) -> usize

1.0.0fn last(self) -> Option<Self::Item>

1.0.0fn nth(&mut self, n: usize) -> Option<Self::Item>

1.0.0fn chain<U>(self, other: U) -> Chain<Self, U::IntoIter> where U: IntoIterator<Item=Self::Item>

1.0.0fn zip<U>(self, other: U) -> Zip<Self, U::IntoIter> where U: IntoIterator

1.0.0fn map<B, F>(self, f: F) -> Map<Self, F> where F: FnMut(Self::Item) -> B

1.0.0fn filter<P>(self, predicate: P) -> Filter<Self, P> where P: FnMut(&Self::Item) -> bool

1.0.0fn filter_map<B, F>(self, f: F) -> FilterMap<Self, F> where F: FnMut(Self::Item) -> Option<B>

1.0.0fn enumerate(self) -> Enumerate<Self>

1.0.0fn peekable(self) -> Peekable<Self>

1.0.0fn skip_while<P>(self, predicate: P) -> SkipWhile<Self, P> where P: FnMut(&Self::Item) -> bool

1.0.0fn take_while<P>(self, predicate: P) -> TakeWhile<Self, P> where P: FnMut(&Self::Item) -> bool

1.0.0fn skip(self, n: usize) -> Skip<Self>

1.0.0fn take(self, n: usize) -> Take<Self>

1.0.0fn scan<St, B, F>(self, initial_state: St, f: F) -> Scan<Self, St, F> where F: FnMut(&mut St, Self::Item) -> Option<B>

1.0.0fn flat_map<U, F>(self, f: F) -> FlatMap<Self, U, F> where U: IntoIterator, F: FnMut(Self::Item) -> U

1.0.0fn fuse(self) -> Fuse<Self>

1.0.0fn inspect<F>(self, f: F) -> Inspect<Self, F> where F: FnMut(&Self::Item) -> ()

1.0.0fn by_ref(&mut self) -> &mut Self

1.0.0fn collect<B>(self) -> B where B: FromIterator<Self::Item>

1.0.0fn partition<B, F>(self, f: F) -> (B, B) where F: FnMut(&Self::Item) -> bool, B: Default + Extend<Self::Item>

1.0.0fn fold<B, F>(self, init: B, f: F) -> B where F: FnMut(B, Self::Item) -> B

1.0.0fn all<F>(&mut self, f: F) -> bool where F: FnMut(Self::Item) -> bool

1.0.0fn any<F>(&mut self, f: F) -> bool where F: FnMut(Self::Item) -> bool

1.0.0fn find<P>(&mut self, predicate: P) -> Option<Self::Item> where P: FnMut(&Self::Item) -> bool

1.0.0fn position<P>(&mut self, predicate: P) -> Option<usize> where P: FnMut(Self::Item) -> bool

1.0.0fn rposition<P>(&mut self, predicate: P) -> Option<usize> where P: FnMut(Self::Item) -> bool, Self: ExactSizeIterator + DoubleEndedIterator

1.0.0fn max(self) -> Option<Self::Item> where Self::Item: Ord

1.0.0fn min(self) -> Option<Self::Item> where Self::Item: Ord

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

1.6.0fn max_by_key<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 F: FnMut(&Self::Item) -> B, B: Ord

1.6.0fn min_by_key<B, F>(self, f: F) -> Option<Self::Item> where F: FnMut(&Self::Item) -> B, B: Ord

1.0.0fn rev(self) -> Rev<Self> where Self: DoubleEndedIterator

1.0.0fn unzip<A, B, FromA, FromB>(self) -> (FromA, FromB) where Self: Iterator<Item=(A, B)>, FromB: Default + Extend<B>, FromA: Default + Extend<A>

1.0.0fn cloned<'a, T>(self) -> Cloned<Self> where Self: Iterator<Item=&'a T>, T: 'a + Clone

1.0.0fn cycle(self) -> Cycle<Self> where Self: Clone

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

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

1.5.0fn cmp<I>(self, other: I) -> Ordering where I: IntoIterator<Item=Self::Item>, Self::Item: Ord

1.5.0fn partial_cmp<I>(self, other: I) -> Option<Ordering> where I: IntoIterator, Self::Item: PartialOrd<I::Item>

1.5.0fn eq<I>(self, other: I) -> bool where I: IntoIterator, Self::Item: PartialEq<I::Item>

1.5.0fn ne<I>(self, other: I) -> bool where I: IntoIterator, Self::Item: PartialEq<I::Item>

1.5.0fn lt<I>(self, other: I) -> bool where I: IntoIterator, Self::Item: PartialOrd<I::Item>

1.5.0fn le<I>(self, other: I) -> bool where I: IntoIterator, Self::Item: PartialOrd<I::Item>

1.5.0fn gt<I>(self, other: I) -> bool where I: IntoIterator, Self::Item: PartialOrd<I::Item>

1.5.0fn ge<I>(self, other: I) -> bool where I: IntoIterator, Self::Item: PartialOrd<I::Item>

Derived Implementations

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

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

1.0.0fn clone_from(&mut self, source: &Self)