pub(crate)fncapitalize_first_letter(s:&str)-> String{// Unicode case conversion can change the length of the string, so we can't capitalize in place.
// Instead we extract the first character and convert it to uppercase. This returns
// an iterator which we collect into a string, and then append the rest of the input.
letmut c = s.chars();match c.next(){None=>String::new(),Some(f)=> f.to_uppercase().collect::<String>()+ c.as_str(),}}