wcstod (3)
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 widecharacter string to a doubleprecision numberSYNOPSIS
#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
The functionality described on this reference page is aligned with the ISO C standard. Any conflict between the requirements described here and the ISO C standard is unintentional. This volume of POSIX.12008 defers to the ISO C standard. These functions shall convert the initial portion of the widecharacter string pointed to by nptr to double, float, and long double representation, respectively. First, they shall decompose the input widecharacter string into three parts: 1.
 An initial, possibly empty, sequence of whitespace widecharacter codes (as specified by iswspace())
 2.
 A subject sequence interpreted as a floatingpoint constant or representing infinity or NaN
 3.
 A final widecharacter string of one or more unrecognized widecharacter codes, including the terminating null widecharacter code of the input widecharacter string Then they shall attempt to convert the subject sequence to a floatingpoint number, and return the result. The expected form of the subject sequence is an optional '+' or '' sign, then one of the following:
 *
 A nonempty sequence of decimal digits optionally containing a radix character; then an optional exponent part consisting of the wide character 'e' or the wide character 'E', optionally followed by a '+' or '' wide character, and then followed by one or more decimal digits
 *
 A 0x or 0X, then a nonempty sequence of hexadecimal digits optionally containing a radix character; then an optional binary exponent part consisting of the wide character 'p' or the wide character 'P', optionally followed by a '+' or '' wide character, and then followed by one or more decimal digits
 *
 One of INF or INFINITY, or any other wide string equivalent except for case
 *

One of NAN or NAN(nwcharsequenceopt), or any other wide string ignoring case in the NAN part, where:


nwcharsequence: digit nondigit nwcharsequence digit nwcharsequence nondigit

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 nwchar sequences is implementationdefined. 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 implementationdefined manner. The radix character shall be as defined in the current 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 implementationdefined 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. These functions 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 dqL<=D<=Udq. 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
fscanf(), iswspace(), localeconv(), setlocale(), wcstol() The Base Definitions volume of POSIX.12008, Chapter 7, Locale, <float.h>, <wchar.h>COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology  Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 7, Copyright (C) 2013 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. (This is POSIX.12008 with the 2013 Technical Corrigendum 1 applied.) 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 www.unix.org/online.html .Any typographical or formatting errors that appear in this page are most likely to have been introduced during the conversion of the source files to man page format. To report such errors, see www.kernel.org/doc/manpages/reporting_bugs.html .