jason.functions.RuleToFunction Maven / Gradle / Ivy
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package jason.functions;
import jason.JasonException;
import jason.asSemantics.DefaultArithFunction;
import jason.asSemantics.TransitionSystem;
import jason.asSemantics.Unifier;
import jason.asSyntax.InternalActionLiteral;
import jason.asSyntax.Literal;
import jason.asSyntax.LiteralImpl;
import jason.asSyntax.NumberTerm;
import jason.asSyntax.Term;
import jason.asSyntax.VarTerm;
import java.util.Iterator;
/**
Wraps a rule into a function. For example the rule
sum(X,Y,Z) :- Z = X+Y.
is wrapped in a function sum(X,Y).
To define sum as
a function the user should register it using a
directive in the ASL code:
{ register_function("myf.sum",2,"sum") }
where myf.sum is the name of the function,
sum is the name of the rule (or literal, or
internal action) and 2 is the function's arity.
@author Jomi
*/
public class RuleToFunction extends DefaultArithFunction {
private final String literal;
private final int arity;
public RuleToFunction(String literal, int arity) {
this.literal = literal;
this.arity = arity;
}
@Override
public String getName() {
return super.getName()+"_{"+literal+"}";
}
@Override
public boolean checkArity(int a) {
return a == arity;
}
@Override
public boolean allowUngroundTerms() {
return true;
}
@Override
public double evaluate(TransitionSystem ts, Term[] args) throws Exception {
// create a literal to perform the query
Literal r;
if (literal.indexOf(".") > 0) // is internal action
r = new InternalActionLiteral(literal);
else
r = new LiteralImpl(literal);
r.addTerms(args);
VarTerm answer = new VarTerm("__RuleToFunctionResult");
r.addTerm(answer);
// query the BB
Iterator i = r.logicalConsequence( (ts == null ? null : ts.getAg()), new Unifier());
if (i.hasNext()) {
Term value = i.next().get(answer);
if (value.isNumeric())
return ((NumberTerm)value).solve();
else
throw new JasonException("The result of "+r+" (="+value+") is not numeric!");
} else
throw new JasonException("No solution was found for rule "+r);
}
public String toString() {
return "function wrapper for "+literal+"/"+arity;
}
}