Macro smart_read::try_read

macro_rules! try_read {
    () => { ... };
    ([$default:expr]) => { ... };
    ($custom_input:expr) => { ... };
    ([$default:expr] $custom_input:expr) => { ... };
    (= $($choice:expr),*) => { ... };
    ([$default:expr] = $($choice:expr),*) => { ... };
}

same as read!(), but returns a result