public void extend(String variable,Collection<Value> vals){
  Set<Assignment> newGroundings=new HashSet<Assignment>();
  for (  Assignment g : groundings) {
    for (    Value v : vals) {
      newGroundings.add(new Assignment(g,variable,v));
    }
  }
  groundings=newGroundings;
}

public void extend ( String variable , Collection < Value > vals ) { Set < Assignment > newGroundings = new HashSet < Assignment > ( ) ; for ( Assignment g : groundings ) { for ( Value v : vals ) { newGroundings . add ( new Assignment ( g , variable , v ) ) ; } } groundings = newGroundings ; }
extend a set of groundings with the alternative values for the variable
