std::stof, std::stod, std::stold - cppreference.com (original) (raw)

Defined in header
float stof ( const std::string& str, std::size_t* pos = nullptr );	(1)	(since C++11)
float stof ( const std::wstring& str, std::size_t* pos = nullptr );	(2)	(since C++11)
double stod ( const std::string& str, std::size_t* pos = nullptr );	(3)	(since C++11)
double stod ( const std::wstring& str, std::size_t* pos = nullptr );	(4)	(since C++11)
long double stold( const std::string& str, std::size_t* pos = nullptr );	(5)	(since C++11)
long double stold( const std::wstring& str, std::size_t* pos = nullptr );	(6)	(since C++11)

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.

[edit] Parameters

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

[edit] Return value

The string converted to the specified floating point type.

[edit] 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.

[edit] Example

[edit] Defect reports

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

DR	Applied to	Behavior as published	Correct behavior
LWG 2009	C++11	std::out_of_range would not be thrown if the convertedvalue would fall out of the range of the result type	will throw
LWG 2403	C++11	stof called std::strtod or std::wcstod	stof calls std::strtof or std::wcstof

[edit] See also

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