Struct core::iter::Unfold
[−]
[src]
pub struct Unfold<St, F> {
pub state: St,
// some fields omitted
}Unstable
An iterator that passes mutable state to a closure and yields the result.
Examples
An iterator that yields sequential Fibonacci numbers, and stops on overflow.
#![feature(core)] extern crate core; fn main() { use std::iter::Unfold; // This iterator will yield up to the last Fibonacci number before the max // value of `u32`. You can simply change `u32` to `u64` in this line if // you want higher values than that. let mut fibonacci = Unfold::new((Some(0u32), Some(1u32)), |&mut (ref mut x2, ref mut x1)| { // Attempt to get the next Fibonacci number // `x1` will be `None` if previously overflowed. let next = match (*x2, *x1) { (Some(x2), Some(x1)) => x2.checked_add(x1), _ => None, }; // Shift left: ret <- x2 <- x1 <- next let ret = *x2; *x2 = *x1; *x1 = next; ret }); for i in fibonacci { println!("{}", i); } }#![feature(core)] use std::iter::Unfold; // This iterator will yield up to the last Fibonacci number before the max // value of `u32`. You can simply change `u32` to `u64` in this line if // you want higher values than that. let mut fibonacci = Unfold::new((Some(0u32), Some(1u32)), |&mut (ref mut x2, ref mut x1)| { // Attempt to get the next Fibonacci number // `x1` will be `None` if previously overflowed. let next = match (*x2, *x1) { (Some(x2), Some(x1)) => x2.checked_add(x1), _ => None, }; // Shift left: ret <- x2 <- x1 <- next let ret = *x2; *x2 = *x1; *x1 = next; ret }); for i in fibonacci { println!("{}", i); }
Fields
state | Unstable 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>
Unstable
Creates a new iterator with the specified closure as the "iterator function" and an initial state to eventually pass to the closure