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std::to_string

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< cpp‎ | string‎ | basic string
 
 
 
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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)

Contents

[edit] Parameters

value - a numeric value to convert

[edit] Return value

A string holding the converted value.

[edit] Exceptions

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

[edit] 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

[edit] 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

[edit] See also

converts an integral or floating-point value to wstring
(function) [edit]
(C++11)(C++11)
converts a string to an unsigned integer
(function) [edit]
(C++11)(C++11)(C++11)
converts a string to a signed integer
(function) [edit]
(C++11)(C++11)(C++11)
converts a string to a floating point value
(function) [edit]
(C++17)
converts an integer or floating-point value to a character sequence
(function) [edit]