ctype functions only apply to ascii, but
I'm sure there are similar libraries for UTF-8, etc.
Most of the ctype functions translate easily into
forth with one or two tests, using, for
example, 'within', in combination with bit
operations ( 'and', 'or', 'xor', etc. ) and basic
I'm sure you could "cook in" the library bindings
in your Gforth build, but I'm not sure it's worth the
effort to do this for all light-use bindings.
There is one exception: ctype's 'IsGraphic()'
gives its answer based on the default locale
specified to the C compiler.
Most forths also provide versions of, at least
one of, 'to-upper', 'to-lower' or 'flip-case'; for
searching the dictionary.