Convert Float to String In C++

In this article, we learn how we can convert float to string in C++ using different methods: 

• Using the to_string()
• Using stringstream
• Using Macros
• Using lexical_cast from the boost library

1. Using to_string()

The to_string() method takes a single integer variable or other data type and converts it into a string.

Syntax: –

string to_string (float value);

Example:

C++

#include <bits/stdc++.h>
using namespace std;

int main() {
    float x=5.5;
      string resultant;
      resultant=to_string(x);
    cout << "Converted value from float to String using to_string() is : "<<resultant<<endl;
    return 0;
}

Output

Converted value from float to String using to_string() is : 5.500000

Explanation: The to_string function converts the given float value into the string.

2. Using stringstream 

A stringstream associates a string object with a stream allowing you to read from the string as if it were a stream (like cin). To use stringstream, we need to include sstream header file. The stringstream class is extremely useful in parsing input. The basic methods are:

• clear() – To clear the stream.
• str() – To get and set a string object whose content is present in the stream. 
• operator <<- Add a string to the stringstream object. 
• operator >>- Read something from the stringstream object.

Example:

C++

#include <bits/stdc++.h>
using namespace std;

int main() {

      float x=5.5;
      stringstream s;
      s<<x; // appending the float value to the streamclass
      string result=s.str(); //converting the float value to string
    cout <<"Converted value from float to String using stringstream is : "<<result<<endl;
    return 0;
}

Output

Converted value from float to String using stringstream is : 5.5

Explanation: The stringstream class converts the float value from a variable to a string. It is an inbuilt class present in the C++ Library.

3. Using Macros

This method solely applies to floating point conversion. The ‘#’ is used by the STRING macro to convert the floating-point values to String.

Syntax: 

#define STRING(Value) #Value
string gfg(STRING(Float_value));

Example:

C++

#include <bits/stdc++.h>
#include <string>
using namespace std;
//using macro to convert float to string
#define STRING(Value) #Value

int main() {
    string gfg(STRING(5.5));
    if(gfg.empty()) cout << "The String is empty"<<endl ;
    else cout << gfg << endl;

    return EXIT_SUCCESS;
}

Output

5.5

4. Using lexical_cast 

Boost.LexicalCast which is defined in the Library “boost/lexical_cast.hpp” provides a cast operator, boost::lexical_cast, that can convert numbers from strings to numeric types like int or double and vice versa. boost::lexical_cast is an alternative to functions like std::stoi(), std::stod(), and std::to_string(), which were added to the standard library in C++11. 

Syntax:

float x= 5.5;
string res = lexical_cast<string>(x);

Example:

C++

#include "boost/lexical_cast.hpp"
#include <bits/stdc++.h>
using namespace std;
using boost::lexical_cast;
using boost::bad_lexical_cast;
int main() {
   // Float to string conversion
  float x= 5.5;
  string res = lexical_cast<string>(x);
  cout << res << endl;
  return 0;
}

Output:

5.5