peg::parser!{
pub grammar url_parser() for str {
rule number() -> u32
= n:$(['0'..='9']+) {? n.parse().or(Err("u32")) }
pub rule list() -> Vec<u32>
= "[" l:(number() ** ",") "]" { l }
#[no_eof]
pub rule scheme() -> String
= s:$(['a'..='z' | '0'..='9' | '-' | '.']+) ":" { s.to_string() }
}
}