package G4ip;

import java.util.Vector;

import G4ip.Form.*;

/** Context acts as a multiset.<p>

  * Typical contexts in logical rules are Gamma, Delta, etc.

  * @author      Christian Urban

  */

public class Context extends Vector {

  public Context() { super(); }

  public Context(Context init_context) {

    super();

    for (int i=0;i<init_context.size();i++) {

      addElement(init_context.elementAt(i));

    }

  }

  /** should be toString, but this is a "final" method in Vector 

    */

  public String makeString() {

    String s = new String();

    int i;                      // size()-1 because the last formula

    for (i=0;i<size()-1;i++) {  // should be printed without a comma

      s=s.concat(elementAt(i).toString());

      s=s.concat(", ");

    }

    if (size() > 0) {           // add last formula 

      s=s.concat(elementAt(i).toString()); 

    }

    return s;

  }

  /** returns a context with one additional formula at the beginning 

    * @param   new_formula    a formula

    */

  public Context add(Form new_formula) {

    Context new_c = new Context(this);

    new_c.insertElementAt(new_formula,0);

    return new_c;

  }

  /** returns a context with two additional formulae at the beginning 

    * @param new_formula1,new_formula2    two formulae

    */

  public Context add(Form new_formula1, Form new_formula2) {

    Context new_c = new Context(this);

    new_c.insertElementAt(new_formula1,0);

    new_c.insertElementAt(new_formula2,0);

    return new_c;

  }

  /** tests whether a context contains a specific atom 

    * @param a a formula

    */

  public boolean includes(Form a) {

    if (a instanceof Atm) {

      for (int i=0;i<size();i++) {

        switch((Form)elementAt(i)) {

        case Atm(String c):

          if (c.compareTo(((Atm)a).c) == 0) return true; break;

        }

      }

    }

    return false;

  }

}