| // Copyright 2017 The Rust Project Developers. See the COPYRIGHT |
| // file at the top-level directory of this distribution and at |
| // http://rust-lang.org/COPYRIGHT. |
| // |
| // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or |
| // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license |
| // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your |
| // option. This file may not be copied, modified, or distributed |
| // except according to those terms. |
| |
| fn iterate<T, F>(initial: T, f: F) -> Iterate<T, F> { |
| Iterate { |
| state: initial, |
| f: f, |
| } |
| } |
| |
| pub struct Iterate<T, F> { |
| state: T, |
| f: F |
| } |
| |
| impl<T: Clone, F> Iterator for Iterate<T, F> where F: Fn(&T) -> T { |
| type Item = T; |
| |
| #[inline] |
| fn next(&mut self) -> Option<Self::Item> { |
| self.state = (self.f)(&self.state); |
| Some(self.state.clone()) |
| } |
| #[inline] |
| fn size_hint(&self) -> (usize, Option<usize>) { (std::usize::MAX, None) } |
| } |
| |
| fn main() { |
| let a = iterate(0, |x| x+1); |
| println!("{:?}", a.iter().take(10).collect::<Vec<usize>>()); |
| //~^ ERROR no method named `iter` found for type `Iterate<{integer} |
| } |
