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

From cppreference.com
< cpp‎ | string‎ | basic string

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

Interprets a floating point value in a string `str`.

1) calls std::strtod(str.c_str(), pos)
2) calls std::strtod(str.c_str(), pos)
3) calls std::strtold(str.c_str(), pos)

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 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 a decimal point character (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 (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.

The index of the first unconverted character is stored in `pos`. If NULL is passed as `pos`, it is ignored.

### [edit] Parameters

str | - | the string to convert
pos | - | address of integer to store the index of the first unconverted character

### [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 (`strtod` or `strtold`) sets errno to ERANGE.

### [edit] See also

stoi stol stoll (C++11)(C++11)(C++11) | converts a string to a signed integer (function) [edit]
stoul stoull (C++11)(C++11) | converts a string to an unsigned integer (function) [edit]

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