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How can I check if a predicate exists in a Prolog program? That would be an exists/1, like:
?- exists(some_predicate).
false.
?- assert(some_predicate).
true.
?- exists(some_predicate).
true.
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Prolog in Artificial Intelligence The not predicate is used to negate some statement, which means, when a statement is true, then not(statement) will be false, otherwise if the statement is false, then not(statement) will be true. If X and Y match, then different(X,Y) fails, Otherwise different(X,Y) succeeds.
This predicate is used to make a list of all solutions X, from the predicate P. The returned list will be L. So we will read this as “find all of the Xs, such that X is a solution of predicate P and put the list of results in L”. Here this predicate stores the results in the same order, in which Prolog finds them.
Prolog predicate is the method to contain the argument and return the boolean values such as true or false. It is a function to operate and return given values, variables, or arguments using a prolog programming language.
You can use current_predicate/1, current_predicate/2 or predicate_property/2 (for the last you will probably need functor/3):
?- current_predicate(a/1).
false.
?- functor(A,a,1),predicate_property(A,visible).
false.
?- functor(A,a,1),current_predicate(_,A).
false.
?- assert(a(42)).
true.
?- current_predicate(a/1).
true.
?- functor(A,a,1),predicate_property(A,visible).
A = a(_G136).
?- functor(A,a,1),current_predicate(_,A).
A = a(_G122).
current_predicate/2 and predicate_property/2 (with visible) succeeds if the predicate can be autoloaded while currrent_predicate/1 fails
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