Shared via Rust Playground

playground.rs

fn get_c() -> Box<FnMut(i32)> {
    Box::new(|val: i32| {
        println!("value --> {}", val);
    })
}

pub fn set_c<F>(mut callback: F)
    where F: FnMut(i32)
{
    callback(100);
}

fn main() {
    let mut cb = get_c();

    set_c(|x| cb(x));
    set_c(|val: i32| println!("value --> {}", val));
}

I had some discussion regarding passing closures returned from a function to another function as an argument --> http://is.gd/O1V2pj . I could make this
| work by using &mut F for closure parameter. Is there a way to make this work with out using reference?
0246 rtrt | pub fn set_c<F: ?Sized>(callback: &mut F)where F: FnMut(i32){} --> This works well
0247 rtrt | What if it is a 3rd party library and this is out the function is defined --> pub fn set_c(callback: F) where F: FnMut(i32)
0248 --> | Flat ([email protected]) has joined #rust-beginners
0249 @mbrubec+| rtrt: I guess you could call it as set_c(|x| cb(x))
0249 @mbrubec+| closures within closures...
0249 @mbrubec+| http://is.gd/Ai5ZTi