Sentence.h

#ifndef SEQUENCE_H_INCLUDED
#define SEQUENCE_H_INCLUDED

#include <vector>
#include <iostream>
using namespace std;

template<typename T>
class Iterator
{
private:

  static const int iteratorEnd = -1;
  vector<T>& elements;
  int next;
  Iterator(vector<T>& elements, int next) : elements(elements), next(next) { }

public:

  static Iterator begin(vector<T>& elements)
  {
    if(elements.size() == 0)
      return end(elements);

    return Iterator(elements, 0);
  }

  static Iterator end(vector<T>& elements)
  {
    return Iterator(elements, iteratorEnd);
  }

  bool operator!=(Iterator& other)
  {
    return this->elements != other.elements || this->next != other.next;
  }

  Iterator& operator++()
  {
    ++this->next;
    if(this->next >= this->elements.size())
      this->next = iteratorEnd;

    return *this;
  }

  T& operator*()
  {
    return this->elements[this->next];
  }
};

template<typename T, typename Generator>
class Sequence
{
private:

  Generator generator;
  vector<T> elements{ };
public:

  void generateNext(int counter)
  {
    for(int i = 0; i < counter; ++i)
      this->elements.emplace_back(this->generator());
  }

  Iterator<T> begin()
  {
    return Iterator<T>::begin(this->elements);
  }

  Iterator<T> end()
  {
    return Iterator<T>::end(this->elements);
  }
};

#endif // SEQUENCE_H_INCLUDED