static Map<Character, Cell> scanMap (final char[][] map, final Set<Cell> lambdas) {
      lambdas.clear();

      final Map<Character, Cell> items = new HashMap<>();
      for (int row = 0; row < map.length; row++) {
         for (int col = 0; col < map[row].length; col++) {
            switch (map[row][col]) {
            case '\\':
               lambdas.add(new Cell(row, col));
               break;
            case 'R':
               items.put('R', new Cell(row, col));
               break;
            case 'L':
               items.put('L', new Cell(row, col));
               break;
            case 'O':
               items.put('O', new Cell(row, col));
               break;
            default: // no-op
               break;
            }
         }
      }

      return items;
   }