wctrans_t wctrans(const char *charclass);
The wctrans() function is defined for valid character mapping names identified in the current locale. The charclass is a string identifying a generic character mapping name for which codeset-specific information is required. The following character mapping names are defined in all locales: tolower and toupper.
The function shall return a value of type wctrans_t, which can be used as the second argument to subsequent calls of towctrans(). The wctrans() function shall determine values of wctrans_t according to the rules of the coded character set defined by character mapping information in the program's locale (category LC_CTYPE ). The values returned by wctrans() shall be valid until a call to setlocale() that modifies the category LC_CTYPE .
The wctrans() function shall return 0 and may set errno to indicate the error if the given character mapping name is not valid for the current locale (category LC_CTYPE ); otherwise, it shall return a non-zero object of type wctrans_t that can be used in calls to towctrans().
The wctrans() function may fail if:
The following sections are informative.
towctrans() , the Base Definitions volume of IEEE Std 1003.1-2001, <wctype.h>