public void addVertex(ValueGraphVertex v){
  if (vertices.add(v)) {
    if (v.representsParameter()) {
      nParameter++;
    }
    if (representativeV == null) {
      representativeV=v;
    }
  }
}

public void addVertex ( ValueGraphVertex v ) { if ( vertices . add ( v ) ) { if ( v . representsParameter ( ) ) { nParameter ++ ; } if ( representativeV == null ) { representativeV = v ; } } }
add a vertex to this congruence class .
