Returning a simpler Iterator interface instead of a Map in Rust

Question

I\'d like to write this:

fn fibs() -> std::iter::Iterator {
    return std::iter::iterate((1i, 1i), |(a, b)| { (b, a + b) }).map(|(a, _)| a)
}
         


        

Answer 1

There is not at present any way to return an abstract type such as Iterator, just as you can’t assign that as the type of a variable (let x: Iterator; won’t compile for the same reasons).

This has been discussed and is certainly desired; when it is done it will probably be in the form fn fibs() -> impl Iterator, but you can’t do that yet.