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

Revision as of 12:54, 16 August 2011

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Interprets a floating point value in a string str. The index of the first unconverted character is stored in pos. If Template:cpp is passed as pos, it is ignored.

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

Parameters

Return value

The string converted to the specified floating point type.

Exceptions

Template:cpp if no conversion could be performed

Template:cpp if the converted value would fall out of the range of the result type.

See also