wcstof

       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 representa-
       tion, respectively. First, they shall decompose the input  wide-charac-
       ter 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 rep-
           resenting 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  option-
          ally  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
       a  hexadecimal floating-point number, an exponent part of the appropri-
       ate 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 (cate-
       gory 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 success-
       ful.

       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:


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 cor-
       rectly rounded. If the subject sequence D has the decimal form and more
       than  DECIMAL_DIG  significant digits, consider the two bounding, adja-
       cent decimal strings L and U, both having DECIMAL_DIG significant  dig-
       its,  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 round-
       ing 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 .



IEEE/The Open Group                  2003                            WCSTOD(P)