Macro map 

macro_rules! map {
    () => { ... };
    (B) => { ... };
    ($(||)+) => { ... };
    (B $(||)+) => { ... };
    ($($k: expr => $v: expr),+ $(,)*) => { ... };
    (B $($k: expr => $v: expr),+ $(,)*) => { ... };
}

HashMap/BTreeMap operations

NOTE: The B prefix variants (e.g. map!{B 1 => 2}) are deprecated. Use bmap! instead.