wcstod - Convert a wide-character string to a double-precision
value
#include <wchar.h>
double wcstod(
const wchar_t *ws,
wchar_t **endptr );
Standard C Library (libc)
Interfaces documented on this reference page conform to
industry standards as follows:
wcstod(): XSH5.0
Refer to the standards(5) reference page for more information
about industry standards and associated tags.
Points to the wide-character string to be converted to
double-precision floating-point value. Points to a
pointer in which the wcstod() function stores the position
of the final wide-character segment of the string, which
contains unrecognized characters and the null terminator.
The wcstod() function converts the initial portion of the
wide-character string pointed to by the ws parameter to a
double-precision floating-point value. The input widecharacter
string is first broken down into three parts: an
initial (possibly empty) sequence of white-space widecharacter
codes (as specified by the iswspace() function);
a subject sequence interpreted as a floating-point constant;
and a final wide-character string of one or more
unrecognized wide-character codes, including the terminating
null wide character. The subject sequence is then (if
possible) converted to a floating-point number and
returned as the result of the wcstod() function.
The subject sequence is expected to consist of an optional
+ (plus sign) or - (minus sign), a nonempty sequence of
digits (which may contain a radix character), and an
optional exponent. The exponent consists of e or E, followed
by an optional sign, followed by one or more decimal
digits. The subject sequence is the longest initial subsequence
of the input wide-character string (starting with
the first nonwhite-space wide-character code) that is of
the expected form. The subject sequence contains no widecharacter
codes if the input wide-character string is
empty or consists entirely of white-space wide-character
codes, or if the first nonwhite-space wide-character code
is other than a sign, a digit, or a radix character.
If the subject sequence is valid, the sequence of widecharacter
codes, starting with the first digit or radix
character (whichever occurs first), is interpreted as a
floating-point or double-precision floating-point
constant. The locale's radix character is treated as
equivalent to the . (period) within floating-point constants
in the C locale. If neither an exponent or radix
character appears, a radix character is assumed to follow
the last digit in the wide-character string. If the subject
sequence begins with - ( a minus sign), the conversion
value is negated. The radix character is determined
by the LC_NUMERIC category in the program's current
locale. In the C locale, or in a locale where the radix
character is not defined, the radix character is a .
(period).
The wcstod() function stores a pointer to the final widecharacter
segment of the string (starting with the first
invalid character) in the object pointed to by the endptr
parameter, unless the endptr parameter is a null pointer.
The wcstod() function returns the converted value of a
double-precision floating-point value if a valid floatingpoint
constant is found. If the converted value is outside
the range of representable values (either too high or too
low), the function returns plus or minus HUGE_VAL and sets
errno to [ERANGE]. If the converted value would cause
underflow, the function returns 0 (zero) and sets errno to
[ERANGE]. If the subject sequence is empty or does not
have the expected form, the function performs no conversion
and returns 0 (zero). In this case, the value specified
by the ws parameter is stored in the object pointed
to by the endptr parameter, provided that the endptr
parameter is not a null pointer.
Since the wcstod() function returns 0 (zero) or HUGE_VAL
in the event of an error and these values are also valid
returns if the wcstod() function is successful, applications
should set errno to 0 (zero) before each call to the
wcstod() function and check errno after each return from
the function. If errno is nonzero after a return, an error
occurred. Additionally, if 0 (zero) is returned, applications
should check if the endptr parameter equals the nptr
parameter. In this case, there was no valid subject
string.
If the following condition occurs, the wcstod() function
sets errno to the corresponding value: The converted value
would cause underflow or, if outside the range of representable
values, overflow.
Functions: atof(3), iswspace(3), localeconv(3), scanf(3),
setlocale(3), wcstol(3)
Standards: standards(5)
wcstod(3)
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