Shared via Rust Playground

playground.rs

fn title_case(s: &str) -> String {
    let mut c = s.chars();
    match c.next() {
        None => String::new(),
        Some(f) => f.to_uppercase().chain(c.flat_map(|t| t.to_lowercase())).collect(),

    }
}

fn main() {
    let s = "foo-bar_baz-QUAX";

    let us = s.split('-').map(|v| title_case(v)).collect::<Vec<_>>().join("-");
    
    println!("{}", us);

}