gb_trees:largest/1

返回最大的键和值

用法：

largest(Tree) -> {Key, Val}

内部实现：

-spec largest(Tree) -> {Key, Val} when
      Tree :: gb_tree(),
      Key :: term(),
      Val :: term().

largest({_, Tree}) ->
    largest_1(Tree).

largest_1({Key, Value, _Smaller, nil}) ->
    {Key, Value};
largest_1({_Key, _Value, _Smaller, Larger}) ->
    largest_1(Larger).

返回一个 {Key, Val} 的元组，Key 是树里最大的键，Val 是与键相关联的值（这里假设这里树不是一个空树）。

Orddict = orddict:from_list([{pear, 7}, {orange, 5}, {apple, 2}]),
Tree = gb_trees:from_orddict(Orddict),
gb_trees:largest(Tree).