Appreciate some help #3:

[tcklnbrg]

How do I define a new type that has several constraints including not
being one of several other types?

In particular, I have defined types: keyword; booleanliteral;
nullliteral, etc. and now I need to define another
type, identifier, as not a keyword, and not a booleanliteral, and not a
null literal , and as a string with constraints on
its form.

something like:

:- type keyword ---> <some enumerated words>.
:- type booleanliteral ---> true; false.
:- type nullliteral ---> null.
:- type identifier ---> \+keyword, \+booleanliteral, \+nullliteral, <and
some other string-related constraints>.


Also, how do I convert types, as in send a string literal into something
that takes a keyword type?


Thanks again for any help---greatly appreciated.


Ann Tecklenburg