package tarau.jinni;

/**
 * Maps a Term to an Source for iterating over its arguments
 */
class TermSource extends Source {
  TermSource(Nonvar val,Prog p) {
    super(p);
    this.val=val;
    pos=0;
  }

  private Nonvar val;
  private int pos;

  public Term getElement() {
    Term X;
    if(null==val) X=null;
    else if(!(val instanceof Fun)) {
      X=val;
      val=null;
    }
    else if(0==pos) X=new Const(val.name());
    else if(pos<=((Fun)val).getArity()) X=((Fun)val).getArg(pos-1);
    else {
      X=null;
      val=null;
    }
    pos++;
    return X;
  }

  public void stop() {
    val=null;
  }
}