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Difference between revisions of "cpp/string/basic string/stof"

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< cpp‎ | string‎ | basic string
(specified in terms of strtox)
(typo)
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Interprets a floating point value in a string {{tt|str}}.  
 
Interprets a floating point value in a string {{tt|str}}.  
  
−
@1@ calls {{c|std::strtod(str.c_str(), pos)}}
+
@1@ calls {{c|std::strtof(str.c_str(), pos)}}
 
@2@ calls {{c|std::strtod(str.c_str(), pos)}}
 
@2@ calls {{c|std::strtod(str.c_str(), pos)}}
 
@3@ calls {{c|std::strtold(str.c_str(), pos)}}
 
@3@ calls {{c|std::strtold(str.c_str(), pos)}}

Revision as of 04:51, 3 December 2013

 
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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::strtof(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 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

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

Contents

Parameters

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

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 (strtod or strtold) sets errno to ERANGE.

See also

(C++11)(C++11)(C++11)
 converts a string to a signed integer
(function) [edit]
(C++11)(C++11)
 converts a string to an unsigned integer
(function) [edit]
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