/// A parser which indexes arguments, but requires allocation, and all related datatypes.
/// A parser which doesn't index arguments or allocate, but requires redundant work, and all related
/// datatypes.
// pub trait Parser {
// #[must_use]
// fn positional(&self, idx: usize) -> Option<&'static str>;
//
// #[must_use]
// fn flag(&self, name: &'static str) -> bool;
//
// #[must_use]
// fn option(&self, name: &'static str) -> Option<OptValues>;
// }