std::to_string - cppreference.com (original) (raw)

Defined in header
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)

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)

[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 #include #include #include #include #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

[edit] See also

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