Convert an integer (decimal) to string in C++

Welcome to Logically Proven blog.
This post demonstrates how to convert an integer to a string in C++.

There are two ways to achieve this functionality.

1) using stringstream
2)using to_string function (C++ 11)

Using stringstream: (better if you are not using latest version)

#include<iostream>
#include<string>
#include<sstream>
using namespace std;

 string itos(int i) // convert int to string
 {
  stringstream s;
  s << i;
  return s.str();
 }

 int main()
 {
  int i = 128;
  string ss= itos(i);
  const char* p = ss.c_str();

  cout << ss << " " << p << "\n";
 }

This technique works for converting any type that you can output using <<.

Using to_string function:

Converts a numerical value to std::string

The following functions are available in string library since C++ 11 version to convert numeric to string .

std::string to_string(int value); //converts a signed decimal to string
std::string to_string(long value); //converts a signed long decimal to string
std::string to_string(long long value); //converts a signed long long decimal to string
std::string to_string(unsigned value); //converts an unsigned decimal to string
std::string to_string(unsigned long value); //converts an unsigned long decimal to string
std::string to_string(unsigned long long value); //converts an unsigned long long decimal to string
std::string to_string(float value); //converts a float value to string
std::string to_string(double value); //converts double float value to string
std::string to_string(long double value); //converts long double float value to string

These functions takes 'value' as a parameter and returns a string equivalent.

Example:

#include <iostream>
#include <string>
 
int main() 
{
    double dVal = 28.28;
    std::string d_str = std::to_string(dVal);
    std::cout << d_str << '\n';
}

//output: 28.280000

You may run into some errors in the second case if your compiler doesn't support. The error message is
"to_string is not a member of std".  In this case please follow this link how to fix -
http://stackoverflow.com/questions/12975341/to-string-is-not-a-member-of-std-says-so-g

Please write your comments if you find anything is incorrect or do you want to share more information about the topic discussed above.

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Karthik Byggari

Author & Editor

Computer Science graduate, Techie, Founder of logicallyproven, Love to Share and Read About pprogramming related things.