std::to_string (3) - Linux Manuals

std::to_string: std::to_string

NAME

std::to_string - std::to_string

Synopsis

Defined in header <string>
std::string to_string( int value ); (1) (since C++11)
std::string to_string( long value ); (2) (since C++11)
std::string to_string( long long value ); (3) (since C++11)
std::string to_string( unsigned value ); (4) (since C++11)
std::string to_string( unsigned long value ); (5) (since C++11)
std::string to_string( unsigned long long value ); (6) (since C++11)
std::string to_string( float value ); (7) (since C++11)
std::string to_string( double value ); (8) (since C++11)
std::string to_string( long double value ); (9) (since C++11)

Converts a numeric value to std::string.
1) Converts a signed decimal integer to a string with the same content as what std::sprintf(buf, "%d", value) would produce for sufficiently large buf.
2) Converts a signed decimal integer to a string with the same content as what std::sprintf(buf, "%ld", value) would produce for sufficiently large buf.
3) Converts a signed decimal integer to a string with the same content as what std::sprintf(buf, "%lld", value) would produce for sufficiently large buf.
4) Converts an unsigned decimal integer to a string with the same content as what std::sprintf(buf, "%u", value) would produce for sufficiently large buf.
5) Converts an unsigned decimal integer to a string with the same content as what std::sprintf(buf, "%lu", value) would produce for sufficiently large buf.
6) Converts an unsigned decimal integer to a string with the same content as what std::sprintf(buf, "%llu", value) would produce for sufficiently large buf.
7,8) Converts a floating point value to a string with the same content as what std::sprintf(buf, "%f", value) would produce for sufficiently large buf.
9) Converts a floating point value to a string with the same content as what std::sprintf(buf, "%Lf", value) would produce for sufficiently large buf.

Parameters

value - a numeric value to convert

Return value

a string holding the converted value

Exceptions

May throw std::bad_alloc from the std::string constructor.

Notes

* With floating point types std::to_string may yield unexpected results as the number of significant digits in the returned string can be zero, see the example.
* The return value may differ significantly from what std::cout prints by default, see the example.
* std::to_string relies on the current locale for formatting purposes, and therefore concurrent calls to std::to_string from multiple threads may result in partial serialization of calls. C++17 provides std::to_chars as a higher-performance locale-independent alternative.

Example

// Run this code

  #include <iostream>
  #include <string>

  int main()
  {
      double f = 23.43;
      double f2 = 1e-9;
      double f3 = 1e40;
      double f4 = 1e-40;
      double f5 = 123456789;
      std::string f_str = std::to_string(f);
      std::string f_str2 = std::to_string(f2); // Note: returns "0.000000"
      std::string f_str3 = std::to_string(f3); // Note: Does not return "1e+40".
      std::string f_str4 = std::to_string(f4); // Note: returns "0.000000"
      std::string f_str5 = std::to_string(f5);
      std::cout << "std::cout: " << f << '\n'
                << "to_string: " << f_str << "\n\n"
                << "std::cout: " << f2 << '\n'
                << "to_string: " << f_str2 << "\n\n"
                << "std::cout: " << f3 << '\n'
                << "to_string: " << f_str3 << "\n\n"
                << "std::cout: " << f4 << '\n'
                << "to_string: " << f_str4 << "\n\n"
                << "std::cout: " << f5 << '\n'
                << "to_string: " << f_str5 << '\n';
  }

Output:

  std::cout: 23.43
  to_string: 23.430000

  std::cout: 1e-09
  to_string: 0.000000

  std::cout: 1e+40
  to_string: 10000000000000000303786028427003666890752.000000

  std::cout: 1e-40
  to_string: 0.000000

  std::cout: 1.23457e+08
  to_string: 123456789.000000