wctrans_t wctrans(const char *property);
wctrans constructs a value of type wctrans_t that describes a mapping between wide characters identified by the string argument property.
If property identifies a valid mapping of wide characters in the current locale, wctrans returns a nonzero value that is valid as the second argument to towctrans; otherwise, it returns zero.
The only mappings supported are "tolower" and "toupper".