Method selection

src/laybasic/laybasic/layParsedLayerSource.cc:156–212

  }

  bool selection (std::set<db::properties_id_type> &ids) const
  {
    //  this algorithm computes the "or" of two sets by using this relationship: a or b or c or .. = !((!a) and (!b) and (!c) and ..)

    //  get the selection of the first operand into ids
    std::vector<const PropertySelectorBase *>::const_iterator b = m_args.begin ();
    bool inv = (*b)->selection (ids);
    if (m_op == Or) {
      inv = !inv;
    }

    for (++b; b != m_args.end () && !(ids.empty () && !inv); ++b) {

      //  get the selection of the next operand into ids2
      std::set<db::properties_id_type> ids2;
      bool inv2 = (*b)->selection (ids2);
      if (m_op == Or) {
        inv2 = !inv2;
      }

      //  compute the intersection of ids and ids2 in place int ids
      if (ids2.empty () && !inv2) {
        //  shortcut: if the second operand is empty, just clear and terminate the loop then
        ids.clear ();
        inv = false;
      } else if (!inv && !inv2) {
        for (std::set<db::properties_id_type>::iterator id = ids.begin (); id != ids.end (); ) {
          std::set<db::properties_id_type>::iterator i = id;
          ++id;
          if (ids2.find (*i) == ids2.end ()) {
            ids.erase (i);
          }
        }
      } else if (inv && inv2) {
        for (std::set<db::properties_id_type>::iterator id = ids2.begin (); id != ids2.end (); ++id) {
          ids.insert (*id);
        }
      } else {
        //  swap current and new ids such that inv==false
        if (inv) {
          std::swap (inv, inv2);
          ids.swap (ids2);
        }
        //  from ids subtract all ids that are in ids2 (inv2==true!)
        for (std::set<db::properties_id_type>::iterator id = ids.begin (); id != ids.end (); ) {
          std::set<db::properties_id_type>::iterator i = id;
          ++id;
          if (ids2.find (*i) != ids2.end ()) {
            ids.erase (i);
          }
        }
      }

    }

    return m_op == Or ? !inv : inv;
  }