C++ array access with automatic dirty flag set.

dirty_array.cpp

#include <iostream>
#include <stdio.h>
#include <string.h>

using namespace std;

template<int N>
class X
{
    private:
        int data[N];
        class Proxy
        {
            private:
                X<N>& parent;
                int index;
            public:
                Proxy(X<N>& p, int x) : parent(p), index(x){}
                void operator=(int i)
                {
                    if (i != parent.data[index])
                    {
                        parent.dirty = true;
                    }
                    parent.data[index] = i;
                }
                operator int const &()
                {
                    return parent.data[index];
                }
                int operator++(int)
                {
                    parent.data[index]++;
                    parent.dirty = true;
                    return parent.data[index];
                }
        };
    public:
        bool dirty;
        X<N>()
        {
            memset(data,0,N*sizeof(int));
            dirty = false;
        }
        Proxy operator[](int index)
        {
            return Proxy(*this,index);
        }
};

int main()
{
    X<3> sample;
    for (int i = 0;i < 3;i++)
    {
        printf("%d %d\n",(int)sample[i],sample.dirty);
    }
    sample[1] = 0;
    for (int i = 0;i < 3;i++)
    {
        printf("%d %d\n",(int)sample[i],sample.dirty);
    }
    sample[1]++;
    for (int i = 0;i < 3;i++)
    {
        printf("%d %d\n",(int)sample[i],sample.dirty);
    }
}