c++ 谓词中使用了关键字operator重载()小括号

template <typename T1, typename T2>
class AbsLess {
public:
    bool operator()(T1& t1, T2& t2)
    {
        return t1 < t2;
    }
};

operator加()，是仿函数

https://www.cnblogs.com/youxin/archive/2012/07/09/2582530.html

用法参考：

https://www.cnblogs.com/txwtech/p/18643016

https://www.cnblogs.com/txwtech/p/18636908