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Jason is a fully-fledged interpreter for an extended version of AgentSpeak, a BDI agent-oriented logic programming language.

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package jason.stdlib;

import jason.JasonException;
import jason.asSemantics.DefaultInternalAction;
import jason.asSemantics.InternalAction;
import jason.asSemantics.TransitionSystem;
import jason.asSemantics.Unifier;
import jason.asSyntax.StringTerm;
import jason.asSyntax.Structure;
import jason.asSyntax.Term;

/**

  Internal action: .fail.

  
Description: fails the intention where it is run (an internal action that
  always returns false).

  
Example:


   .fail.

  

 */
public class fail extends DefaultInternalAction {

    private static InternalAction singleton = null;
    public static InternalAction create() {
        if (singleton == null)
            singleton = new fail();
        return singleton;
    }

    @Override
    public Object execute(TransitionSystem ts, Unifier un, Term[] args) throws Exception {
        if (args.length > 0) { // add all arguments as annotations in the exception
            // find message
            Term smsg = null;
            String msg = "fail";
            for (Term t: args) {
                if (t.isStructure() && ((Structure)t).getFunctor().equals("error_msg")) {
                    smsg = t;
                    Term tm = ((Structure)t).getTerm(0);
                    if (tm.isString())
                        msg = ((StringTerm)tm).getString();
                    else
                        msg = tm.toString();
                    break;
                }
            }

            JasonException e = new JasonException(msg);
            for (Term t: args) {
                if (t != smsg)
                    e.addErrorAnnot(t);
            }
            throw e;
        }
        return false;
    }
}