<cwctype>
The <cwctype> header is the C++ version of the C standard <wctype.h> header, which declares types
and functions for classifying and converting wide characters.
Most of the functions in this header are wide equivalents of
functions found in <cctype>.
For example, iswalnum determines
whether a wide character is alphanumeric, just as isalnum determines whether a narrow (byte)
character is alphanumeric. The behavior of the wide functions is similar
to their narrow equivalents. In particular, for any narrow character
c, its wide character equivalent
wc, and classification functions
isxyz and iswxyx, if isxyz(c) is true, then iswxyz(wc) is true and vice versa. The only
exception is that iswgraph and
iswpunct behave slightly differently
than isgraph and ispunct for whitespace characters other than
' ‘.
The behavior of the <cwctype> functions depend on the C
locale, as set with the setlocale
function in <clocale>. For more
flexibility in dealing with multiple locales, you can use C++ locales,
in particular the ctype facet in
<locale>.