Function select_user_input 

pub fn select_user_input<T, M, R>(
    t: &T,
    rs: &mut dyn Iterator<Item = (&R, Update<T, M>)>,
) -> Option<Update<T, M>>
where
    T: Uniplate + Display,
    R: Rule<T, M> + Display,

Selects an Update based on user input through stdin.

See the module-level documentation for more information.