struct Clf {
    x: f64
}

let c = Clf { x : 0 };
let v = Vec![-1, 0.5, 1];
println!("{}", c(0.5));     // prints 1
println!("{}", c(v));       // prints [0, 1, 1]

impl Fn for Clf{
    extern "rust-call" fn call ...
    ...
}