How do I clone a closure, so that their types are the same?

Question

I have a struct which looks something like this:

pub struct MyStruct
where
    F: Fn(usize) -> f64,
{
    field: usize,
    mapper: F,
    // fie         


        

Answer 1

As of Rust 1.26.0, closures implement both Copy and Clone if all of the captured variables do:

#[derive(Clone)]
pub struct MyStruct
where
    F: Fn(usize) -> f64,
{
    field: usize,
    mapper: F,
}

fn main() {
    let f = MyStruct {
        field: 34,
        mapper: |x| x as f64,
    };
    let g = f.clone();
    println!("{}", (g.mapper)(3));
}