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

float       stof ( const std::string& str, std::size_t* pos = nullptr );

float       stof ( const std::wstring& str, std::size_t* pos = nullptr );

double      stod ( const std::string& str, std::size_t* pos = nullptr );

double      stod ( const std::wstring& str, std::size_t* pos = nullptr );

long double stold( const std::string& str, std::size_t* pos = nullptr );

long double stold( const std::wstring& str, std::size_t* pos = nullptr );

Interprets a floating point value in a string str.

Let ptr be an internal (to the conversion functions) pointer of type char* (1,3,5) or wchar_t* (2,4,6), accordingly.

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 to base 10)
• hexadecimal 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 to base 2)
• 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 ptr 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

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 (std::strtof, std::strtod or std::strtold) sets errno to ERANGE.

Example

Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

See also