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

      final Map<Character, Cell> result = 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':
               result.put ('R', new Cell (row, col));
               break;
            case 'L':
               result.put ('L', new Cell (row, col));
               break;
            case 'O':
               result.put ('O', new Cell (row, col));
               break;
            default: // no-op
            }
         }
      }

      return result;
   }