ostreamMethods.cpp

#include <iostream>
#include <vector>

using namespace std;

/** Method 1 - Using friend operator in struct or class with public attributes **/
    struct vec2D_1 {
        public: vector<vector<int>> v;

        vec2D_1(vector<vector<int>> v_){
        v = v_;
        }

        friend std::ostream& operator<<(std::ostream& os, const vec2D_1& vec) {
            os << "[";
            for (int i = 0; i < vec.v.size(); ++i) {
                os << "[";
                for (int j = 0; j < vec.v[i].size(); ++j) {
                    os << vec.v[i][j];
                    if (j != vec.v[i].size() - 1)
                        os << ", ";
                }
                if (i != vec.v.size() - 1)
                    os << "],\n";
            }
            os << "]]\n";

            return os;
        }
    };


/** Method 2 - Using operator (out) in struct or class with public attributes **/
    struct vec2D_2 {
        public: vector<vector<int>> v;

        vec2D_2(vector<vector<int>> v_){
         v = v_;
        }
    };

    std::ostream& operator<<(std::ostream& os, const vec2D_2& vec) {
         os << "[";
        for (int i = 0; i < vec.v.size(); ++i) {
            os << "[";
            for (int j = 0; j < vec.v[i].size(); ++j) {
                os << vec.v[i][j];
                if (j != vec.v[i].size() - 1)
                    os << ", ";
            }
            if (i != vec.v.size() - 1)
                os << "],\n";
        }
        os << "]]\n";

        return os;
    }


/** Method 3 - Using operator directly with type **/
    // Override operator<< for my data structure **/
    using Y = vector<vector<int>>;
    std::ostream& operator<<(std::ostream& os, const Y& vec) {
         os << "[";
        for (int i = 0; i < vec.size(); ++i) {
            os << "[";
            for (int j = 0; j < vec[i].size(); ++j) {
                os << vec[i][j];
                if (j != vec[i].size() - 1)
                    os << ", ";
            }
            if (i != vec.size() - 1)
                os << "],\n";
        }
        os << "]]\n";

        return os;
    }



int main(){
    cout << vec2D_1({{0,5,5},{0,5,5}}) << endl;
  
    cout << vec2D_2({{0,5,5},{0,5,5}}) << endl;

    cout <<  vector<vector<int>>({{0,5,5},{0,5,5}}) << endl;

    cout << Y({{0,5,5},{0,5,5}}) << endl; 
}

/*** Excution ***/
/** Excution 
* using MSVS compiler: "cl /EHsc ostream.cpp & ostream.exe"
* using gcc or mingw compiler: "g++ -o ostream ostream.cpp & ostream.exe"
* using clang compiler: "clang++ -o ostream ostream.cpp; ./ostream"
**/