std:: to_string

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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 C locale for formatting purposes, and therefore concurrent calls to std::to_string from multiple threads may result in partial serialization of calls.
- The results of overloads for integer types do not rely on the current C locale, and thus implementations generally avoid access to the current C locale in these overloads for both correctness and performance. However, such avoidance is not guaranteed by the standard.

(until C++26)

C++17 provides std::to_chars as a higher-performance locale-independent alternative.

Feature-test macro	Value	Std	Feature
`__cpp_lib_to_string`	202306L	(C++26)	Redefining `std::to_string` in terms of std::format

Example

Run this code

#include <cstdio>
#include <format>
#include <initializer_list>
#include <iostream>
#include <string>
 
#if __cpp_lib_to_string >= 202306L
constexpr auto revision() { return " (post C++26)"; }
#else
constexpr auto revision() { return " (pre C++26)"; }
#endif
 
int main()
{
    for (const double f : {1.23456789555555, 23.43, 1e-9, 1e40, 1e-40, 123456789.0})
    {
        std::cout << "to_string:\t" << std::to_string(f) << revision() << '\n';
 
        // Before C++26, the output of std::to_string matches std::printf.
        std::printf("printf:\t\t%f\n", f);
 
        // As of C++26, the output of std::to_string matches std::format.
        std::cout << std::format("format:\t\t{}\n", f);
 
        std::cout << "std::cout:\t" << f << "\n\n";
    }
}

Possible output:

to_string:      1.234568 (pre C++26)
printf:         1.234568
format:         1.23456789555555
std::cout:      1.23457
 
to_string:      23.430000 (pre C++26)
printf:         23.430000
format:         23.43
std::cout:      23.43
 
to_string:      0.000000 (pre C++26)
printf:         0.000000
format:         1e-09
std::cout:      1e-09
 
to_string:      10000000000000000303786028427003666890752.000000 (pre C++26)
printf:         10000000000000000303786028427003666890752.000000
format:         1e+40
std::cout:      1e+40
 
to_string:      0.000000 (pre C++26)
printf:         0.000000
format:         1e-40
std::cout:      1e-40
 
to_string:      123456789.000000 (pre C++26)
printf:         123456789.000000
format:         123456789
std::cout:      1.23457e+08

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Classes
basic_string
basic_string_view (C++17)
char_traits

to_wstring (C++11)	converts an integral or floating-point value to `wstring` (function)
stoul stoull (C++11) (C++11)	converts a string to an unsigned integer (function)
stoi stol stoll (C++11) (C++11) (C++11)	converts a string to a signed integer (function)
stof stod stold (C++11) (C++11) (C++11)	converts a string to a floating point value (function)
to_chars (C++17)	converts an integer or floating-point value to a character sequence (function)