The classification functions are also generalized by the ISO C
standard. Instead of just allowing the two standard mappings, a
locale can contain others. Again, the localedef program
already supports generating such locale data files.
— Data Type: wctrans_t
This data type is defined as a scalar type which can hold a value
representing the locale-dependent character mapping. There is no way to
construct such a value apart from using the return value of the
wctrans function.
The wctrans function has to be used to find out whether a named
mapping is defined in the current locale selected for the
LC_CTYPE category. If the returned value is non-zero, you can use
it afterwards in calls to towctrans. If the return value is
zero no such mapping is known in the current locale.
Beside locale-specific mappings there are two mappings which are
guaranteed to be available in every locale:
towctrans maps the input character wc
according to the rules of the mapping for which desc is a
descriptor, and returns the value it finds. desc must be
obtained by a successful call to wctrans.
This function is declared in wctype.h.
For the generally available mappings, the ISO C standard defines
convenient shortcuts so that it is not necessary to call wctrans
for them.
— Function: wint_t towlower (wint_t wc)
If wc is an upper-case letter, towlower returns the corresponding
lower-case letter. If wc is not an upper-case letter,
wc is returned unchanged.
towlower can be implemented using
towctrans (wc, wctrans ("tolower"))
This function is declared in wctype.h.
— Function: wint_t towupper (wint_t wc)
If wc is a lower-case letter, towupper returns the corresponding
upper-case letter. Otherwise wc is returned unchanged.
towupper can be implemented using
towctrans (wc, wctrans ("toupper"))
This function is declared in wctype.h.
The same warnings given in the last section for the use of the wide
character classification functions apply here. It is not possible to
simply cast a char type value to a wint_t and use it as an
argument to towctrans calls.
Published under the terms of the GNU General Public License
