public void add(Predicate p){
  if (m_clauses.contains(p)) {
    throw new IllegalArgumentException("Duplicate predicate.");
  }
  m_clauses.add(p);
  fireExpressionChange();
}

public void add ( Predicate p ) { if ( m_clauses . contains ( p ) ) { throw new IllegalArgumentException ( "Duplicate predicate." ) ; } m_clauses . add ( p ) ; fireExpressionChange ( ) ; }
add a new clause .
