How to assert new rule from user input (PROLOG)

Question

I want to accept users' input, i.e. [garfield, hates, blacky]. hates/2 doesn't exist currently.

In my database,

process:-
    read(Input_List),
    add_rule(Input_List).

add_rule([X, Predicate, Y]):-
    assertz(Predicate(X, Y)).

But this doesn't work. Is it possible to use a variable as predicate, and facts? Or is there any other way to achieve this?

Answer 1

You can use the (=..)/2 operator called univ operator :

add_rule(X, Predicate, Y) :-
    Fact =.. [Predicate, X, Y],
    assertz(Fact).

Usage :

?- add_rule(garfield, hates, blacky).
true.

?- hates(garfield, blacky).
true.