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WCSTOD(3P)                 POSIX Programmer's Manual                WCSTOD(3P)

PROLOG
       This  manual  page is part of the POSIX Programmer's Manual.  The Linux
       implementation of this interface may differ (consult the  corresponding
       Linux  manual page for details of Linux behavior), or the interface may
       not be implemented on Linux.
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 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
       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 num-
       ber, 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  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:
       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  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 Def-
       initions  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(3P)