Prolog解析输出

Question

I'm doing a piece of university coursework, and I'm stuck with some Prolog.

The coursework is to make a really rudimentary Watson (the machine that answers questions on Jeapoardy).

Anyway, I've managed to make it output the following:

noun_phrase(det(the),np2(adj(traitorous),np2(noun(tostig_godwinson)))),
verb_phrase(verb(was),np(noun(slain)))).

But the coursework specifies that I now need to extract the first and second noun, and the verb, to make a more concise sentence; ie [Tostig_godwinson, was, slain].

I much prefer programming in languages like C etc., so I'm a bit stuck. If this were a procedural language, I'd use parsing tools, but Prolog doesn't have any... What do I need to do to extract those parts?

Thank you in advance

Answer 1

In Prolog, the language is the parsing tool. Use the univ ( =.. ) operator to do term inspection:

% find terminal nodes (words) in Tree
terminal(Tree, Type, Item) :-
    Tree =.. [Type, Item],
    atomic(Item).
terminal(Tree, Type, Item) :-
    Tree =.. [_, Sub],
    member(Node, Sub),
    terminal(Node, Type, Item).

Now get a list of all nouns with findall(N, terminal(Tree, noun, N), Nouns) and get the nth1 element.