futures 0.1.10

An implementation of futures and streams featuring zero allocations, composability, and iterator-like interfaces.
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15

//! Definition of the `Option` (optional step) combinator

use {Future, Poll, Async};

impl<F, T, E> Future for Option<F> where F: Future<Item=T, Error=E> {
    type Item = Option<T>;
    type Error = E;

    fn poll(&mut self) -> Poll<Option<T>, E> {
        match *self {
            None => Ok(Async::Ready(None)),
            Some(ref mut x) => x.poll().map(|x| x.map(Some)),
        }
    }
}