Cpp Standard Library 简明教程
C++ Library - <tuple>
Introduction
这些是将不同类型的元素打包到单个对象中的对象，就像对元素对执行的 pair 对象一样，但适用于多个元素。它与 pair 类（在 header 中定义）密切相关：可以从 pair 构建元组，并且在特定目的下 pair 可以被视为元组。
These are objects that pack elements of -possibly- different types together in a single object, just like pair objects do for pairs of elements, but generalized for any number of elements. It is closely related to the pair class (defined in header ): Tuples can be constructed from pairs, and pairs can be treated as tuples for certain purposes.