Sequence.cpp

#include <iostream>
#include <vector>
template <class T>
class Sequence
{
    private: 
    std::vector<T> data;

    public: 
    Sequence(const T &a0, std::size_t k, std::function<T(const T&)> next)
    {
        data.push_back(a0);

        for (std::size_t i = 0; i < k - 1; i++)
        {
            data.push_back(next(data[i]));
        }
    }

    T& operator [] (std::size_t index)
    {
        if(index >= data.size())
        {
            throw std::invalid_argument("Invalid index");
        }
        return this->data[index];
    }

    const T& operator [] (std::size_t index) const
    {
        if(index >= data.size())
        {
            throw std::invalid_argument("Inavlid index");
        }
        return this->data[index];
    }

    class SequenceIterator
    {
        private:
        friend class Sequence;
        T* pointer;

        public:
        SequenceIterator(T* pointer)
        {
            this->pointer = pointer;
        }

        T& operator * ()
        {
            return *pointer;
        }

        const T& operator * () const 
        {
            return *pointer;
        }
        
        SequenceIterator& operator ++ ()
        {
            ++this->pointer;
            return *this;
        }

        SequenceIterator operator ++ (int)
        {
            SequenceIterator old = *this;
            ++(*this);

            return old;
        }

        bool operator == (const SequenceIterator& other) const
        {
            return this->pointer == other.pointer;
        }

        bool operator != (const SequenceIterator& other) const
        {
            return this->pointer != other.pointer;
        }
    };

    SequenceIterator begin()
    {
        return SequenceIterator(&this->data[0]);
    }

    SequenceIterator end()
    {
        return SequenceIterator(&this->data[0] + this->data.size());
    }
};

int p2(int x)
{
    return x + 2;
}
int main()
{
    Sequence<int> even10(0, 10, p2);

    for (int x : even10)
    {
        std::cout << x << " ";
    }

    std::cout << std::endl;
    
}