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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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//----------------------------------------------------------------------------
// Copyright (C) 2003  Rafael H. Bordini, Jomi F. Hubner, et al.
// 
// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Lesser General Public
// License as published by the Free Software Foundation; either
// version 2.1 of the License, or (at your option) any later version.
// 
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
// Lesser General Public License for more details.
// 
// You should have received a copy of the GNU Lesser General Public
// License along with this library; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
// 
// To contact the authors:
// http://www.inf.ufrgs.br/~bordini
// http://www.das.ufsc.br/~jomi
//
//----------------------------------------------------------------------------

package jason.stdlib;

import jason.asSemantics.InternalAction;
import jason.asSemantics.TransitionSystem;
import jason.asSemantics.Unifier;
import jason.asSyntax.ListTerm;
import jason.asSyntax.Term;

/**
  Internal action: .union(S1,S2,S3).

  
Description: S3 is the union of the sets S1 and S2 (represented by lists).
  The result set is sorted.  

  
Parameters:

  + arg[0] (a list).

  
+ arg[1] (a list).

  
+/- arg[2]: the result of the union. 
  

  Examples:

   .union("[a,b,c]","[b,e]",X): X unifies with "[a,b,c,e]".
  
 .union("[a,b,a,c]","[f,e]",X): X unifies with "[a,b,c,e,f]".
  

  @see jason.stdlib.concat
  @see jason.stdlib.delete
  @see jason.stdlib.length
  @see jason.stdlib.member
  @see jason.stdlib.sort
  @see jason.stdlib.substring
  @see jason.stdlib.nth
  @see jason.stdlib.max
  @see jason.stdlib.min
  @see jason.stdlib.reverse
  @see jason.stdlib.difference
  @see jason.stdlib.intersection
*/
public class union extends difference { // to inherit checkArguments
    
    private static InternalAction singleton = null;
    public static InternalAction create() {
        if (singleton == null) 
            singleton = new union();
        return singleton;
    }

    @Override
    public Object execute(TransitionSystem ts, Unifier un, Term[] args) throws Exception {
        checkArguments(args);
        return un.unifies(args[2], ((ListTerm)args[0]).union( (ListTerm)args[1]) );
    }
}