box.rs

fn convert_f32<'a>(input: &'a Vec<f32>) -> Box<Iterator<Item=f32> + 'a> {
    Box::new(input.iter().cloned())
}

fn convert_u32<'a>(input: &'a Vec<u32>) -> Box<Iterator<Item=f32> + 'a> {
    Box::new(input.iter().cloned().map(|x| x as f32))
}

enum InputType {
    Float,
    Int
}

fn main() {
    let a : InputType = InputType::Float;

    let vec_u: Vec<u32> = vec![1, 2, 3];
    let vec_f: Vec<f32> = vec![1.5, 2.5, 3.5];

    let x = match a {
        InputType::Int => convert_u32(&vec_u),
        _ => convert_f32(&vec_f)
    };

    for i in x {
        println!("{}", i);
    }
}