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Linux 2.6 - man page for wcstold (linux section 3posix)

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

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  lan-
       guage,  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 con-
       stant 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 con-
       version 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 char-
       acter 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,  pro-
       vided 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 con-
       version 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 cur-
       rent 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 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 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 orig-
       inal Standard can be obtained online at http://www.opengroup.org/unix/online.html .

IEEE/The Open Group			       2003					WCSTOD(P)


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