fibonnaci_stream/
lib.rs

1//! A lazily evaluated [futures stream](https://docs.rs/futures/*/futures/stream/trait.Stream.html)
2//! of Fibonnaci numbers.
3//!
4//! ## Usage
5//!
6//! ```rust,ignore
7//! extern crate fibonnaci_stream;
8//!
9//! use fibonnaci_stream::{FibError, Stream};
10//!
11//! fn main () {
12//!   let mut stream = FibStream::new();
13//!   stream.poll().and_then(|val| {
14//!     assert_eq!(val, Async::Ready(Some(1)));
15//!
16//!     stream.poll().and_then(|val| {
17//!       assert_eq!(val, Async::Ready(Some(2)));
18//!       Ok(())
19//!     });
20//!
21//!     Ok(())
22//!   });
23//! }
24//! ```
25
26extern crate futures;
27
28pub use futures::Stream;
29use futures::{Async, Future, Poll};
30use std::error::Error;
31
32/// A lazily evaluated [futures stream] of Fibonnaci numbers.
33///
34/// ## Example
35/// ```rust
36/// extern crate fibonnaci_stream;
37/// extern crate futures;
38///
39/// use futures::{Async, Stream}; // Stream must be in scope here for trait to work
40/// use fibonnaci_stream::Stream as FibStream;
41///
42/// fn main () {
43///   let mut stream = FibStream::new();
44///   stream.poll().and_then(|val| {
45///     assert_eq!(val, Async::Ready(Some(1)));
46///     stream.poll().and_then(|val| {
47///       assert_eq!(val, Async::Ready(Some(2)));
48///       Ok(())
49///     });
50///     Ok(())
51///   });
52/// }
53/// ```
54/// [futures stream]: (https://docs.rs/futures/*/futures/stream/trait.Stream.html)
55#[derive(Debug)]
56pub struct FibStream {
57  prev: u64,
58  num: u64,
59}
60
61impl FibStream {
62  /// Creates a new Fibonnaci stream.
63  ///
64  /// This method initializes the stream to start at 1 and continues the
65  /// sequence from there.
66  pub fn new() -> FibStream {
67    FibStream { prev: 0, num: 1 }
68  }
69}
70
71impl Stream for FibStream {
72  type Item = u64;
73  type Error = Box<Error>;
74
75  fn poll(&mut self) -> Poll<Option<Self::Item>, Self::Error> {
76    let res = self.prev + self.num;
77    self.prev = self.num;
78    self.num = res;
79    Ok(Async::Ready(Some(res)))
80  }
81}
82
83impl Future for FibStream {
84  type Item = u64;
85  type Error = Box<Error>;
86
87  fn poll(&mut self) -> Result<Async<u64>, Box<Error>> {
88    let res = self.prev + self.num;
89    self.prev = self.num;
90    self.num = res;
91    Ok(Async::Ready(res))
92  }
93}
fibonnaci_stream/lib.rs

fibonnaci_stream/
lib.rs
