Question

I have written a wrapper class to perform insertion/removal operations on a type vector.
The code:

class GenericSymbolTable {
   public:
       virtual void pushBackAtom(Atom *atom) = 0;
       virtual Atom* peekAtom(void) = 0;
       virtual Atom* getAtom(void) = 0;

   protected:
      ~GenericSymbolTable(void){}
};

class SymbolTable : public GenericSymbolTable {
   private:
       vector<Atom*> atoms;

   protected:
       ~SymbolTable(void);

   public:
       void pushBackAtom(Atom *atom);
       Atom* peekAtom(void);
       Atom* getAtom(void);
};

When writing the implementations for those methods the compiler throws conflicting type errors:

   Atom* SymbolTable::peekAtom(void) {
      if(atoms.empty()) {
          cout << "\t[W] Simbol table does not contain any atoms" << endl;
          return NULL;
      }

      Atom* first = atoms.begin(); // <== type error
      return first;
   }

   Atom* SymbolTable::getAtom(void) {
      if(atoms.empty()) {
          cout << "\t[W] Simbol table does not contain any atoms" << endl;
          return NULL;
      }

      Atom* first = atoms.begin(); // <== type error
      atoms.erase(atoms.begin());
      return first;
   }

Error msg:
cannot convert ‘std::vector::iterator {aka __gnu_cxx::__normal_iterator >}’ to ‘Atom*’ in initialization

Answer 1

  Atom* first = atoms.begin(); // <== type error

This sets first equal to an iterator. You wanted to set it equal to the object the iterator points to. Try:

  Atom* first = *(atoms.begin());

or:

  Atom* first = atoms.front();

Since this is a vector of Atom*, its iterators point to Atom*s.