wcstod, wcstof—wide char string to double or float #include <stdlib.h>
double wcstod(const wchar_t *__restrict str,
wchar_t **__restrict tail);
float wcstof(const wchar_t *__restrict str,
wchar_t **__restrict tail);
double _wcstod_r(void *reent,
const wchar_t *str, wchar_t **tail);
float _wcstof_r(void *reent,
const wchar_t *str, wchar_t **tail);
Description
The function wcstod parses the wide character string str,
producing a substring which can be converted to a double
value. The substring converted is the longest initial
subsequence of str, beginning with the first
non-whitespace character, that has one of these formats:
[+|-]digits[.[digits]][(e|E)[+|-]digits]
[+|-].digits[(e|E)[+|-]digits]
[+|-](i|I)(n|N)(f|F)[(i|I)(n|N)(i|I)(t|T)(y|Y)]
[+|-](n|N)(a|A)(n|N)[<(>[hexdigits]<)>]
[+|-]0(x|X)hexdigits[.[hexdigits]][(p|P)[+|-]digits]
[+|-]0(x|X).hexdigits[(p|P)[+|-]digits]
The substring contains no characters if str is empty, consists
entirely of whitespace, or if the first non-whitespace
character is something other than +, -, ., or a
digit, and cannot be parsed as infinity or NaN. If the platform
does not support NaN, then NaN is treated as an empty substring.
If the substring is empty, no conversion is done, and
the value of str is stored in *tail. Otherwise,
the substring is converted, and a pointer to the final string
(which will contain at least the terminating null character of
str) is stored in *tail. If you want no
assignment to *tail, pass a null pointer as tail.
wcstof is identical to wcstod except for its return type.
This implementation returns the nearest machine number to the
input decimal string. Ties are broken by using the IEEE
round-even rule. However, wcstof is currently subject to
double rounding errors.
The alternate functions _wcstod_r and _wcstof_r are
reentrant versions of wcstod and wcstof, respectively.
The extra argument reent is a pointer to a reentrancy structure.
Returns
HUGE_VAL is returned, and ERANGE is
stored in errno. If the correct value would cause underflow, 0
is returned and ERANGE is stored in errno.
Supporting OS subroutines required: close, fstat, isatty,
lseek, read, sbrk, write.