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wctype.h

wctype.h provides a wide character version of the functions in ctype.h.

Wide character type determination functions​

The following function determines the type of a wide character.

  • iswalnum() tests whether a wide character is alphanumeric
  • iswalpha() tests whether the wide character is alphabetic
  • iswblank() tests whether this is a wide blank character
  • iswcntrl() tests if this is a wide control character
  • iswdigit() tests if this is a wide character that is a number
  • iswgraph() tests if the wide character is a printable non-whitespace character
  • iswlower() tests whether the wide character is lowercase
  • iswprint() tests if the wide character is printable
  • iswpunct() tests whether a wide character is punctuated
  • iswspace() tests if a wide character is a space
  • iswupper() tests if a wide character is uppercase
  • iswxdigit() tests if a wide character is a hexadecimal digit

wctype(), iswctype()​

iswctype()` is a generic version of the various wide character type determination functions in the previous section, and must be used in conjunction with wctype()`.

int iswctype(wint_t wc, wctype_t desc);

iswctype()` accepts two arguments, the first being a wide character whose type needs to be determined, and the second being the wide character type description from the return value of wctype()`.

If the wide character is of the specified type, iswctype() returns a non-zero value, otherwise it returns zero.

wctype() is used to get the type description of a certain kind of wide character.

wctype_t wctype(const char* property);

The argument to wctype() is a given string with the following values available: alnum, alpha, blank, cntrl, digit, graph, lower, print, punct, space, upper, xdigit.

The return value of wctype() is of type wctype_t, which is usually an integer. If the argument is an invalid value, 0 is returned.

if (iswctype(c, wctype("digit")))
// Equivalent to
if (iswdigit(c))

The above example is used to determine whether the wide character c is a numeric value, and is equivalent to iswdigit().

The full type determination for iswctype() is as follows.

iswctype(c, wctype("alnum")) // equivalent to iswalnum(c)
iswctype(c, wctype("alpha")) // equivalent to iswalpha(c)
iswctype(c, wctype("blank")) // equivalent to iswblank(c)
iswctype(c, wctype("cntrl")) // equivalent to iswcntrl(c)
iswctype(c, wctype("digit")) // equivalent to iswdigit(c)
iswctype(c, wctype("graph")) // equivalent to iswgraph(c)
iswctype(c, wctype("lower")) // equivalent to iswlower(c)
iswctype(c, wctype("print")) // equivalent to iswprint(c)
iswctype(c, wctype("punct")) // equivalent to iswpunct(c)
iswctype(c, wctype("space")) // equivalent to iswspace(c)
iswctype(c, wctype("upper")) // equivalent to iswupper(c)
iswctype(c, wctype("xdigit")) // equivalent to iswxdigit(c)

Case conversion functions​

wctype.h provides the following case-sensitive conversion functions for wide characters.

  • towlower() converts uppercase wide characters to lowercase
  • towupper() converts lowercase wide characters to uppercase
  • towctrans() generic function for wide character case conversion
  • wctrans() helper function for case conversion, used in conjunction with towctrans()

See first the example usage of towlower() and towupper().

towlower(L'B') // b
towupper(L'e') // E

The prototypes of towctrans() and wctrans() are as follows.

wint_t towctrans(wint_t wc, wctrans_t desc);
wctrans_t wctrans(const char* property);

Here are examples of their usage.

towctrans(c, wctrans("toupper")) // equivalent to towupper(c)
towctrans(c, wctrans("tolower")) // equivalent to towlower(c)