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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 .