// The `Iterator` trait only requires a method to be defined for the `next` element.
impl Iterator for Fibonacci {
type Item = u32;
// Here, we define the sequence using `.curr` and `.next`.
// The return type is `Option
// * When the `Iterator` is finished, `None` is returned.
// * Otherwise, the next value is wrapped in `Some` and returned.
fn next(&mut self) -> Option
let new_next = self.curr + self.next;
self.curr = self.next;
self.next = new_next;
// Since there's no endpoint to a Fibonacci sequence, the `Iterator`
// will never return `None`, and `Some` is always returned.
Some(self.curr)
}
}
// Returns a Fibonacci sequence generator
fn fibonacci() -> Fibonacci {
Fibonacci { curr: 0, next: 1 }
}
fn main() {
// `0..3` is an `Iterator` that generates: 0, 1, and 2.
let mut sequence = 0..3;
println!("Four consecutive `next` calls on 0..3");
println!("> {:?}", sequence.next());
println!("> {:?}", sequence.next());
println!("> {:?}", sequence.next());
println!("> {:?}", sequence.next());
// `for` works through an `Iterator` until it returns `None`.
// Each `Some` value is unwrapped and bound to a variable (here, `i`).
println!("Iterate through 0..3 using `for`");
for i in 0..3 {
println!("> {}", i);
}
// The `take(n)` method reduces an `Iterator` to its first `n` terms.
println!("The first four terms of the Fibonacci sequence are: ");
for i in fibonacci().take(4) {
println!("> {}", i);
}
// The `skip(n)` method shortens an `Iterator` by dropping its first `n` terms.
println!("The next four terms of the Fibonacci sequence are: ");
for i in fibonacci().skip(4).take(4) {
println!("> {}", i);
}
let array = [1u32, 3, 3, 7];
// The `iter` method produces an `Iterator` over an array/slice.
println!("Iterate the following array {:?}", &array);
for i in array.iter() {
println!("> {}", i);
}
}
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If your function returns a type that implements MyTrait, you can write its return type as -> impl MyTrait. This can help simplify your type signatures quite a lot!
use std::iter;
use std::vec::IntoIter;
// This function combines two `Vec
