#include <wctype.h>
wint_t towctrans(wint_t wc, wctrans_t desc);
The towctrans() function shall transliterate the wide-character code wc using the mapping described by desc. The current setting of the LC_CTYPE category should be the same as during the call to wctrans() that returned the value desc. If the value of desc is invalid (that is, not obtained by a call to wctrans() or desc is invalidated by a subsequent call to setlocale() that has affected category LC_CTYPE ), the result is unspecified.
An application wishing to check for error situations should set errno to 0 before calling towctrans(). If errno is non-zero on return, an error has occurred.
If successful, the towctrans() function shall return the mapped value of wc using the mapping described by desc. Otherwise, it shall return wc unchanged.
The towctrans() function may fail if:
The following sections are informative.
The strings "tolower" and "toupper" are reserved for the standard mapping names. In the table below, the functions in the left column are equivalent to the functions in the right column.
towlower(wc) towctrans(wc, wctrans("tolower"))
towupper(wc) towctrans(wc, wctrans("toupper"))
towlower() , towupper() , wctrans() , the Base Definitions volume of IEEE Std 1003.1-2001, <wctype.h>