NAME

       wcstod, wcstof, wcstold - convert a wide-character string to a double-precision number

SYNOPSIS

       #include <wchar.h>

       double wcstod(const wchar_t *restrict nptr, wchar_t **restrict endptr);
       float wcstof(const wchar_t *restrict nptr, wchar_t **restrict endptr);
       long double wcstold(const wchar_t *restrict nptr,
              wchar_t **restrict endptr);

DESCRIPTION

       These  functions  shall  convert  the  initial portion of the wide-character string pointed to by nptr to
       double, float, and long double representation, respectively. First, they shall decompose the input  wide-
       character string into three parts:

        1. An initial, possibly empty, sequence of white-space wide-character codes (as specified by iswspace())

        2. A subject sequence interpreted as a floating-point constant or representing infinity or NaN

        3. A  final  wide-character  string  of  one  or  more  unrecognized wide-character codes, including the
           terminating null wide-character code of the input wide-character string

       Then they shall attempt to convert the subject sequence  to  a  floating-point  number,  and  return  the
       result.

       The expected form of the subject sequence is an optional plus or minus sign, then one of the following:

        * A  non-empty  sequence  of  decimal  digits  optionally containing a radix character, then an optional
          exponent part

        * A 0x or 0X, then a non-empty sequence of hexadecimal digits optionally containing a  radix  character,
          then an optional binary exponent part

        * One of INF or INFINITY, or any other wide string equivalent except for case

        * One  of  NAN  or  NAN(n-wchar-sequence_opt),  or  any other wide string ignoring case in the NAN part,
          where:

          n-wchar-sequence:
              digit
              nondigit
              n-wchar-sequence digit
              n-wchar-sequence nondigit

       The subject sequence is defined as the longest initial subsequence of the  input  wide  string,  starting
       with  the  first  non-white-space  wide  character,  that  is  of the expected form. The subject sequence
       contains no wide characters if the input wide string is not of the expected form.

       If the subject sequence has the  expected  form  for  a  floating-point  number,  the  sequence  of  wide
       characters  starting  with  the  first  digit  or  the  radix character (whichever occurs first) shall be
       interpreted as a floating constant according to the rules of  the  C  language,  except  that  the  radix
       character  shall be used in place of a period, and that if neither an exponent part nor a radix character
       appears in a decimal floating-point number, or if a binary exponent part does not appear in a hexadecimal
       floating-point  number,  an  exponent  part  of  the appropriate type with value zero shall be assumed to
       follow the last digit in the string. If the subject sequence begins with a minus sign, the sequence shall
       be interpreted as negated. A wide-character sequence INF or INFINITY shall be interpreted as an infinity,
       if representable in the return type, else as if it were a floating constant that is  too  large  for  the
       range of the return type. A wide-character sequence NAN or NAN(n-wchar-sequence_opt) shall be interpreted
       as a quiet NaN, if supported in the return type, else as if it were a subject sequence part that does not
       have  the expected form; the meaning of the n-wchar sequences is implementation-defined. A pointer to the
       final wide string shall be stored in the object pointed to by endptr, provided that endptr is not a  null
       pointer.

       If  the  subject sequence has the hexadecimal form and FLT_RADIX is a power of 2, the conversion shall be
       rounded in an implementation-defined manner.

       The radix character shall be as defined in the program's locale (category  LC_NUMERIC  ).  In  the  POSIX
       locale,  or  in a locale where the radix character is not defined, the radix character shall default to a
       period ( '.' ).

       In other than the C    or POSIX  locales, other implementation-defined subject sequences may be accepted.

       If the subject sequence is empty or does not have the expected form, no conversion  shall  be  performed;
       the  value of nptr shall be stored in the object pointed to by endptr, provided that endptr is not a null
       pointer.

       The wcstod() function shall not change the setting of errno if successful.

       Since 0 is returned on error and is also a valid return on success, an application wishing to  check  for
       error situations should set errno to 0, then call wcstod(), wcstof(), or wcstold(), then check errno.

RETURN VALUE

       Upon  successful  completion, these functions shall return the converted value. If no conversion could be
       performed, 0 shall be returned    and errno may be set to [EINVAL].

       If the correct value is outside the range of representable values, ±HUGE_VAL, ±HUGE_VALF,  or  ±HUGE_VALL
       shall be returned (according to the sign of the value), and errno shall be set to [ERANGE].

       If  the  correct  value  would  cause  underflow, a value whose magnitude is no greater than the smallest
       normalized positive number in the return type shall be returned and errno set to [ERANGE].

ERRORS

       The wcstod() function shall fail if:

       ERANGE The value to be returned would cause overflow or underflow.

       The wcstod() function may fail if:

       EINVAL No conversion could be performed.

       The following sections are informative.

EXAMPLES

       None.

APPLICATION USAGE

       If the subject sequence has the hexadecimal form and FLT_RADIX is not a power of 2, and the result is not
       exactly  representable,  the  result  should be one of the two numbers in the appropriate internal format
       that are adjacent to the hexadecimal floating source value, with the extra  stipulation  that  the  error
       should have a correct sign for the current rounding direction.

       If  the  subject sequence has the decimal form and at most DECIMAL_DIG (defined in <float.h>) significant
       digits, the result should be correctly rounded. If the subject sequence D has the decimal form  and  more
       than  DECIMAL_DIG  significant  digits, consider the two bounding, adjacent decimal strings L and U, both
       having DECIMAL_DIG significant digits, such that the values of L, D, and U satisfy "L <= D <=  U"  .  The
       result should be one of the (equal or adjacent) values that would be obtained by correctly rounding L and
       U according to the current rounding direction, with the extra stipulation that the error with respect  to
       D should have a correct sign for the current rounding direction.

RATIONALE

       None.

FUTURE DIRECTIONS

       None.

SEE ALSO

       iswspace()  ,  localeconv()  ,  scanf()  ,  setlocale()  ,  wcstol()  ,  the  Base  Definitions volume of
       IEEE Std 1003.1-2001, Chapter 7, Locale, <float.h>, <wchar.h>

COPYRIGHT

       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition,
       Standard  for  Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base
       Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics Engineers,
       Inc  and  The  Open Group. In the event of any discrepancy between this version and the original IEEE and
       The Open Group Standard, the original IEEE and The Open Group  Standard  is  the  referee  document.  The
       original Standard can be obtained online at http://www.opengroup.org/unix/online.html .