要将书写函数对象的进程简单化, 标准库提供两个类模板作为这样的对象的基类: std::unary_function 和 std::binary_function. 它们都在头文件 < functional > 中声明. 根据其命名, unary_function 提供接收一个参数的基函数而 binary_function 提供一个接收两个参数的基函数.-Write function to simplify the process of the object, the standard template library provides two types of object such as a base class: std:: unary_function and std:: binary_function. They are all in the first document < functional>　in a statement. In accordance with its name, Receiving a unary_function provide the basis function parameters and binary_function two parameters provide a receiver of the basis function.