std::to_string

 

C++

Compiler support

Freestanding and hosted

Language

Standard library

Standard library headers

Named requirements

Feature test macros (C++20)

Language support library

Concepts library (C++20)

Diagnostics library

Memory management library

Metaprogramming library (C++11)

General utilities library

Containers library

Iterators library

Ranges library (C++20)

Algorithms library

Strings library

Text processing library

Numerics library

Date and time library

Input/output library

Filesystem library (C++17)

Concurrency support library (C++11)

Execution control library (C++26)

Technical specifications

Symbols index

External libraries

 

Strings library

Classes

basic_string

basic_string_view (C++17)

char_traits

 

std::basic_string

Member functions basic_string::basic_string basic_string::~basic_string basic_string::operator= basic_string::assign basic_string::assign_range (C++23)   basic_string::get_allocator Element access basic_string::at basic_string::operator[] basic_string::front (DR*) basic_string::back (DR*) basic_string::data basic_string::c_str basic_string::operator  basic_string_view (C++17) Iterators basic_string::beginbasic_string::cbegin (C++11) basic_string::endbasic_string::cend (C++11) basic_string::rbeginbasic_string::crbegin (C++11) basic_string::rendbasic_string::crend (C++11) Search basic_string::find basic_string::rfind basic_string::find_first_of basic_string::find_first_not_of basic_string::find_last_of basic_string::find_last_not_of

Modifiers basic_string::clear basic_string::insert basic_string::insert_range (C++23) basic_string::erase basic_string::push_back basic_string::pop_back (DR*) basic_string::append basic_string::append_range (C++23) basic_string::operator+= basic_string::replace basic_string::replace_with_range (C++23) basic_string::copy basic_string::resize basic_string::resize_and_overwrite (C++23)  basic_string::swap Capacity basic_string::empty basic_string::sizebasic_string::length basic_string::max_size basic_string::reserve basic_string::capacity basic_string::shrink_to_fit (DR*) Operations basic_string::compare basic_string::starts_with (C++20) basic_string::ends_with (C++20) basic_string::contains (C++23) basic_string::substr

Constants basic_string::npos Non-member functions operator+ swap(std::basic_string) erase(std::basic_string)erase_if(std::basic_string) (C++20)(C++20) I/O operator<<operator>> getline Comparison operator==operator!=operator<operator>operator<=operator>=operator<=> (until C++20)(until C++20)(until C++20)(until C++20)(until C++20)(C++20) Numeric conversions stoistolstoll (C++11)(C++11)(C++11) stoulstoull (C++11)(C++11)  stofstodstold (C++11)(C++11)(C++11) to_string (C++11) to_wstring (C++11) Literals operator""s (C++14) Helper classes hash<std::basic_string> (C++11) Deduction guides (C++17)

 

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

See also

to_wstring (C++11)	converts an integral or floating-point value to wstring (function)
stoulstoull (C++11)(C++11)	converts a string to an unsigned integer (function)
stoistolstoll (C++11)(C++11)(C++11)	converts a string to a signed integer (function)
stofstodstold (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)