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std::to_string

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.

Let buf be an internal to the conversion functions buffer, sufficiently large to contain the result of conversion.

1) Converts a signed integer to a string as if by std::sprintf(buf, "%d", value). 2) Converts a signed integer to a string as if by std::sprintf(buf, "%ld", value). 3) Converts a signed integer to a string as if by std::sprintf(buf, "%lld", value). 4) Converts an unsigned integer to a string as if by std::sprintf(buf, "%u", value). 5) Converts an unsigned integer to a string as if by std::sprintf(buf, "%lu", value). 6) Converts an unsigned integer to a string as if by std::sprintf(buf, "%llu", value). 7,8) Converts a floating point value to a string as if by std::sprintf(buf, "%f", value). 9) Converts a floating point value to a string as if by std::sprintf(buf, "%Lf", value).

(until C++26)

1-9) Converts a numeric value to a string as if by std::format("{}", value). (since C++26)

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

#include <iostream>
#include <string>
 
int main()
{
    for (const double f : {23.43, 1e-9, 1e40, 1e-40, 123456789.0})
        std::cout << "std::cout: " << f << '\n'
                  << "to_string: " << std::to_string(f) << "\n\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