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1 | // Copyright 2017 The Rust Project Developers. See the COPYRIGHT |
2 | // file at the top-level directory of this distribution and at | |
3 | // http://rust-lang.org/COPYRIGHT. | |
4 | // | |
5 | // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or | |
6 | // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license | |
7 | // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your | |
8 | // option. This file may not be copied, modified, or distributed | |
9 | // except according to those terms. | |
10 | ||
11 | fn iterate<T, F>(initial: T, f: F) -> Iterate<T, F> { | |
12 | Iterate { | |
13 | state: initial, | |
14 | f: f, | |
15 | } | |
16 | } | |
17 | ||
18 | pub struct Iterate<T, F> { | |
19 | state: T, | |
20 | f: F | |
21 | } | |
22 | ||
23 | impl<T: Clone, F> Iterator for Iterate<T, F> where F: Fn(&T) -> T { | |
24 | type Item = T; | |
25 | ||
26 | #[inline] | |
27 | fn next(&mut self) -> Option<Self::Item> { | |
28 | self.state = (self.f)(&self.state); | |
29 | Some(self.state.clone()) | |
30 | } | |
31 | #[inline] | |
32 | fn size_hint(&self) -> (usize, Option<usize>) { (std::usize::MAX, None) } | |
33 | } | |
34 | ||
35 | fn main() { | |
36 | let a = iterate(0, |x| x+1); | |
37 | println!("{:?}", a.iter().take(10).collect::<Vec<usize>>()); | |
38 | //~^ ERROR no method named `iter` found for type `Iterate<{integer} | |
39 | } |