wcstold - Convert a wide-character string to a long double-precision
value
#include <wchar.h>
long double wcstold(
const wchar_t *ws,
wchar_t **endptr );
Standard C Library (libc)
Interfaces documented on this reference page conform to
industry standards as follows:
wcstold(): ISO C
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 a
long double-precision floating-point value. Points to a
pointer in which the wcstold() function stores the position
of the final wide-character segment of the string,
which contains unrecognized characters and the null terminator.
The wcstold() function converts the initial portion of the
wide-character string pointed to by the ws parameter to a
long double-precision floating-point value. The input
wide-character string is first broken down into three
parts: an initial (possibly empty) sequence of white-space
wide-character 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 wcstold() 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 wcstold() 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 wcstold() function returns the converted value of a
long double-precision floating-point value if a valid
floating-point 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 wcstold() function returns 0 (zero) or HUGE_VAL
in the event of an error and these values are also valid
returns if the wcstold() function is successful, applications
should set errno to 0 (zero) before each call to the
wcstold() 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 wcstold() 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), wcstod(3), wcstol(3)
Standards: standards(5)
wcstold(3)
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