c++ - Operator Overloading and ostream in the class

Question

#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;

class B
{
    int val;
public:
    B(int v):val(v){}
    int getV() const {return val;}
    bool operator < (const B & v)const {return val<v.val;}
};

ostream & operator <<(ostream & out, const B& v)
{
    out<<v.getV();
    return out;
}

template<class T> struct Out
{
    ostream & out;
    Out(ostream & o): out(o){}
    void operator()(const T& val){out<<val<<" ";}
    
};


int main() {
   
    
    B t1[]={3,2,4,1,5};
    B t2[]={5,6,8,2,1};
    vector<B> v1(10,0);
    sort(t1,t1+5);
    sort(t2,t2+5);
    
    set_union(t1,t1+5,t2,t2+5,v1.begin());
    for_each(v1.begin(),v1.end(), Out<B>(cout)); cout<<endl;
return 0;
}

Hello, I have question about this code.
For now, I study for C++ certification and I study with the study guide book now.
In many questions on the book, I often see the code that

class B
{
    int val;
public:
    B(int v):val(v){}
    int getV() const {return val;}
    bool operator < (const B & v)const {return val<v.val;}
};

ostream & operator <<(ostream & out, const B& v)
{
    out<<v.getV();
    return out;
}

template<class T> struct Out
{
    ostream & out;
    Out(ostream & o): out(o){}
    void operator()(const T& val){out<<val<<" ";}
    
};

I have tried to understand this part but I actually confused how these work, so I would like someone to explain what these codes do.
I really appreciate that if someone answer this question.
Thank you.

question from:https://stackoverflow.com/questions/66057486/operator-overloading-and-ostream-in-the-class

Answer 1

Waitting for answers