// ---- symbol access ----
  #define SYMBOL_ACCESS(Thing)                              \
    /* retrieve, return NULL if not there */                \
    Thing const *find##Thing##C(char const *name) const;    \
    Thing *find##Thing(char const *name)                    \
      { return const_cast<Thing*>(find##Thing##C(name)); }  \
                                                            \
    /* retrieve, or create it if not already there */       \
    Thing *getOrMake##Thing(char const *name);

  SYMBOL_ACCESS(Symbol)        // findSymbolC, findSymbol, getOrMakeSymbol
  SYMBOL_ACCESS(Terminal)      //   likewise
  SYMBOL_ACCESS(Nonterminal)   //   ..
  #undef SYMBOL_ACCESS

  // the inverse of transition: map a target state to the symbol that
  // would transition to that state (from the given source state)
  Symbol const *inverseTransitionC(ItemSet const *source,
                                   ItemSet const *target) const;