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

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

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 alphanumeric characters. 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.

Language
Standard library headers
Concepts
Utilities library
Strings library
Containers library
Algorithms library
Iterators library
Numerics library
Input/output library
Localizations library
Regular expressions library (C++11)
Atomic operations library (C++11)
Thread support library (C++11)
Filesystem library (C++17)
Technical Specifications

Null-terminated strings
Byte strings
Multibyte strings
Wide strings
Classes
basic_string
basic_string_view (C++17)
char_traits

stoistolstoll (C++11)(C++11)(C++11)	converts a string to a signed integer (function)
stoulstoull (C++11)(C++11)	converts a string to an unsigned integer (function)
from_chars (C++17)	converts a character sequence to an integer or floating-point value (function)

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

Parameters

Return value

Exceptions

See also