|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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(longlong value); | (3) | (since C++11) |
std::string to_string(unsigned value); | (4) | (since C++11) |
std::string to_string(unsignedlong value); | (5) | (since C++11) |
std::string to_string(unsignedlonglong 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(longdouble value); | (9) | (since C++11) |
Converts a numeric value tostd::string.
Let 1) Converts a signed integer to a string as if bystd::sprintf(buf,"%d", value). 2) Converts a signed integer to a string as if bystd::sprintf(buf,"%ld", value). 3) Converts a signed integer to a string as if bystd::sprintf(buf,"%lld", value). 4) Converts an unsigned integer to a string as if bystd::sprintf(buf,"%u", value). 5) Converts an unsigned integer to a string as if bystd::sprintf(buf,"%lu", value). 6) Converts an unsigned integer to a string as if bystd::sprintf(buf,"%llu", value). 7,8) Converts a floating point value to a string as if bystd::sprintf(buf,"%f", value). 9) Converts a floating point value to a string as if bystd::sprintf(buf,"%Lf", value). | (until C++26) |
1-9) Converts a numeric value to a string as if bystd::format("{}", value). | (since C++26) |
Contents |
| value | - | a numeric value to convert |
A string holding the converted value.
May throwstd::bad_alloc from thestd::string constructor.
std::to_string may yield unexpected results as the number of significant digits in the returned string can be zero, see the example.std::cout prints by default, see the example.
| (until C++26) |
C++17 providesstd::to_chars as a higher-performance locale-independent alternative.
| Feature-test macro | Value | Std | Feature |
|---|---|---|---|
__cpp_lib_to_string | 202306L | (C++26) | Redefiningstd::to_string in terms ofstd::format |
#include <cstdio>#include <format>#include <initializer_list>#include <iostream>#include <string> #if __cpp_lib_to_string >= 202306Lconstexprauto revision(){return" (post C++26)";}#elseconstexprauto revision(){return" (pre C++26)";}#endif int main(){for(constdouble 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: 1.234568format: 1.23456789555555std::cout: 1.23457 to_string: 23.430000 (pre C++26)printf: 23.430000format: 23.43std::cout: 23.43 to_string: 0.000000 (pre C++26)printf: 0.000000format: 1e-09std::cout: 1e-09 to_string: 10000000000000000303786028427003666890752.000000 (pre C++26)printf: 10000000000000000303786028427003666890752.000000format: 1e+40std::cout: 1e+40 to_string: 0.000000 (pre C++26)printf: 0.000000format: 1e-40std::cout: 1e-40 to_string: 123456789.000000 (pre C++26)printf: 123456789.000000format: 123456789std::cout: 1.23457e+08
(C++11) | converts an integral or floating-point value towstring(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] |
