Hey all,

I'm trying to write a prolog program which kinda keeps track of whats going
on... heres an example;

process([where, is, X], [X, is, in, Y]) :- isin(X,Y).

this is called via another rule called "go", and then rules are checked
etc and putting in [where, is, mcdonalds]. might return [mcdonalds, is,
in, leeds]. thats all fine and dandy, working great.

Now the problem, I have to then implement a [what, is, it] section which
I thought was going to be easy but for the life of me I can't get it to
work as wanted. So yea, if I put in [what, is, it] after the last one I
should get [mcdonalds, is, a, restaurant] which i've got handled. I just
want to know (finally) how to store a global variable of what "it" is.
Something like;

process([where,is,X], [X,is,in,Y]) :- isin(X,Y), GlobalVar = Y.

Was what I was thinking of and then;

process([what,is,it], A) :- process([what,is,GlobalVar], A).

But that doesn't work and just returns (assuming) the variable allocation
pointer or something like that (e.g. _L203). So any help anyone can offer
will be appreciated.

Matt

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"Matt Wilson

Without trying to give you a complete solution, here is something that might help you construct one:

process/2 seems to be something that given a sentence, returns another
sentence + some more information which you want to put in a global variable; I suggest that you
put it as an extra argument in the process predicate, and haps you need 2 of those argument, one that gets
in and one that gets out; the information it carries is related to the focus of the conversation you seem to be
simulating; so it could be a list like [it(macdonalds), where(leeds), when(dunno)]
initially, it is empty; rules for process/4 become a bit more complicated; as an example:

    process([where,is,X],[X,is,in,Y],InfoIn,InfoOut) :-
                        findlocation(InfoIn,Y),
                        update_it(X,InfoIn,InfoOut).

you use process/4 in a recusive predicate like

    conversation(Info) :-
            userinput(User),
            process(User,Answer,Info,NewInfo),
            display_answer(Answer),
            conversation(NewInfo).

Does that work for you ?

Cheers

Bart Demoen

Hrm, OK I think I understand the direction this is going in, i'm trying;

go :-   Git = '',
        write('Please type in a question > '),
        read(Question), process(Question, Answer, Git),
        write(Answer), nl,
        (Question=[bye];go).

process([what, is, X], [X, is, a, Y], X) :- isa(X, Y).
process([what, is, it], A, G) :- process([what, is, G], A, _).

isa(mcdonalds, restaurant).

I tried this (basically, with some more stuff), by executing the rule go.
and then typing in [what, is, mcdonalds]. I expected [mcdonalds, is, a,
restaurant] as the reply with Git now set to "mcdonalds". So when I
execute [what, is, it], it should reply with [mcdonalds, is, a,
restaurant]. *However*, as i'm sure you've realised whats wrong already,
what I get is;

Please type in a question > [what, is, mcdonalds].

No.
?-

Which of course isn't what I wanted. I assume it is because of the final
X in the first process statement with it conflicting with the Git and
member of Question being processed... I'm really confused please give me
some more hints!

Thanks for your help.

Matt

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