Check out example codes for "concat string in c++". It will help you in understanding the concepts better.

Code Example 1

string first_name = "foo"
string last_name = "bar"
std::cout << first_name + " " + last_name << std::endl;

Code Example 2

#include <iostream>
#include <cstdlib>

std::string text = "hello";
std::string moretext = "there";
std::string together = text + moretext;
std::cout << together << std::endl;

>> hello there

Code Example 3

#include <string>
int main() {
	//"Ever thing inside these double quotes becomes const char array"
//	std::string namee = "Caleb" +"Hello";//This will give error because adding const char array to const char array 
	std::string namee = "Caleb";
	namee += " Hello";//This will work because adding a ptr to a actual string
	std::cout << namee << std::endl;// output=>Caleb Hello
//You can also use the below
	std::string namee2 = std::string("Caleb")+" Hello";// This will work because constructor will convert const char array  to string, adding a ptr to string
	std::cout << namee2 << std::endl;// output=>Caleb Hello

Code Example 4

#include <iostream>
#include <sstream>

int main() {
  std::string value = "Hello, " + "world!";
  std::cout << value << std::endl;

  //Or you can use ostringstream and use integers too
  //For example:

  std::ostringstream ss;
  ss << "This is an integer" << 104;
  std::cout << ss.str() << std::endl;

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