message: Make getBytesPerRep pure virtual
diff: @@ -117,7 +117,7 @@ public:
  virtual Index_type getItsPerRep() const { return getRunSize(); }
  - virtual size_t getBytesPerRep() const { return s_unknown_bytes; }
  + virtual size_t getBytesPerRep() const = 0;
  std::string getBytesPerRepStr() const
  {
  size_t bytes = getBytesPerRep();
  