std::stof,std::stod,std::stold (3) - Linux Manuals

std::stof,std::stod,std::stold: std::stof,std::stod,std::stold

NAME

std::stof,std::stod,std::stold - std::stof,std::stod,std::stold

Synopsis

Defined in header <string>
float stof( const std::string& str, std::size_t* pos = 0 ); (1) (since C++11)
float stof( const std::wstring& str, std::size_t* pos = 0 );
double stod( const std::string& str, std::size_t* pos = 0 ); (2) (since C++11)
double stod( const std::wstring& str, std::size_t* pos = 0 );
long double stold( const std::string& str, std::size_t* pos = 0 ); (3) (since C++11)
long double stold( const std::wstring& str, std::size_t* pos = 0 );

Interprets a floating point value in a string str.

1) calls std::strtod(str.c_str(), &ptr) or std::wcstod(str.c_str(), &ptr) (until C++17)
1) calls std::strtof(str.c_str(), &ptr) or std::wcstof(str.c_str(), &ptr) (since C++17)

2) calls std::strtod(str.c_str(), &ptr) or std::wcstod(str.c_str(), &ptr)
3) calls std::strtold(str.c_str(), &ptr) or std::wcstold(str.c_str(), &ptr)
Function discards any whitespace characters (as determined by std::isspace()) until first non-whitespace character is found. Then it takes as many characters as possible to form a valid floating-point representation and converts them to a floating-point value. The valid floating-point value can be one of the following:

* decimal floating-point expression. It consists of the following parts:

      * (optional) plus or minus sign
      * nonempty sequence of decimal digits optionally containing decimal-point character (as determined by the current C locale) (defines significand)
      * (optional) e or E followed with optional minus or plus sign and nonempty sequence of decimal digits (defines exponent)

* binary floating-point expression. It consists of the following parts:

      * (optional) plus or minus sign
      * 0x or 0X
      * nonempty sequence of hexadecimal digits optionally containing a decimal-point character (as determined by the current C locale) (defines significand)
      * (optional) p or P followed with optional minus or plus sign and nonempty sequence of decimal digits (defines exponent)

* infinity expression. It consists of the following parts:

      * (optional) plus or minus sign
      * INF or INFINITY ignoring case

* not-a-number expression. It consists of the following parts:

      * (optional) plus or minus sign
      * NAN or NAN(char_sequence) ignoring case of the NAN part. char_sequence can only contain digits, Latin letters, and underscores. The result is a quiet NaN floating-point value.

* any other expression that may be accepted by the currently installed C locale

If pos is not a null pointer, then a pointer ptr, internal to the conversion functions, will receive the address of the first unconverted character in str.c_str(), and the index of that character will be calculated and stored in *pos, giving the number of characters that were processed by the conversion.

Parameters

str - the string to convert
pos - address of an integer to store the number of characters processed

Return value

The string converted to the specified floating point type.

Exceptions

std::invalid_argument if no conversion could be performed
std::out_of_range if the converted value would fall out of the range of the result type or if the underlying function (
strtof,
(since C++17)strtod or strtold) sets errno to ERANGE.