Re: Accessing instantiated variable in call predicate

Hi,

I am afraid you don't provide nearly enough information, so we cannot give very specific advice. 

Offhand, I can think of three ways of addressing this sort problem:

1. The translator from Sent to Logic Form could produce the list of "interesting" variables that are going to be instantiated by executing LogicForm. Say: the result of s/3 could be of the form
translated( LogicForm, Variables ).   Then your clause would be something like:

    getAtom( Sent, Variables ) :-  
        s( translated( LogicForm, Variables ), Sent, [] ),
        call( LogicForm ).

and the second argument of getAtom/2 would magically have what you want upon exit.


2. If modifying the translator would be too inconvenient, and the number of possible forms produced by s/3 is very limited, then you could write a procedure ("predicate") extract/2 that handles the forms, along the following lines:

    extract( to( chair, A ), [ A ] ).
    extract( from_to( table, A, B ), [ A, B ] ).
    etc.

Again, adding an invocation of this to getAtom would do the trick.


3. If _all_ the variables in a "logic form" are "interesting", then there is a simple general solution: just extract the uninstantiated variables from the LogicForm (before calling it).

    getAtom( Sent, Variables ) :-
        s( LogicForm, Sent, [] ),
        term_variables( LogicForm, Variables ),
	call( LogicForm ).    

(Please notice that term_variables/2 is built-in.)

Hope this helps,
-- Feliks


On Jul 21, 2013, at 12:48, Emanuele Bastianelli <[email protected]> wrote:

> Hi to all,
> 
> i've just started using 'call' predicate, and i was wondering how i can
> access the variable that are instantiated in the predicate that is passed
> to the 'call' predicate as variable.
> For example, this is my case. I've this predicate:
> 
> getAtom(Sent) :- s(LogicForm,Sent,[]), call(LogicForm).
> 
> Now, LogicForm indeed represent the logic form of the analyzed sentence.
> Through the predicate 'call', I execute the query represented by the logic
> form on my KB. Again, the logic form represent a predicate, as:
> 
> to(chair,A)
> 
> where A is the variable that will be instantiated with the value I need to
> retrieve.
> Then, how can i access that value starting from the getAtom predicate? All
> that I can get is the instatiation of the variable LogicForm, as
> 
> LogicForm = to(chair, chair_1)
> 
> while* *I want to get just the chair_1 atom instance.
> 
> Thank you.
> EB
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