대입연산자 없이 NULL을 받을 수도 있나요?

//siterator.h
#ifndef SITERATOR_H
#define SITERATOR_H
#include <iterator>
#include <cstddef>
namespace sstd {
 
 
template<typename T>
class Siterator:public std::iterator<std::random_access_iterator_tag,T> {
private:
public:
	T* pt;
	T* pointer() {
		return pt;
	}
	Siterator() {
		pt=NULL;
	}
	Siterator(T* _pt) {
		pt=_pt;
	}
	Siterator(const Siterator<T>& src):pt(src.pt) {
		//pt=src.pt;
	}
	Siterator& operator++() {
		++pt;
		return *this;
	}
	Siterator operator++(int) {
		Siterator tmp(*this);
		++pt;
		return tmp;
	}
	Siterator& operator--() {
		--pt;
		return *this;
	}
	Siterator operator--(int) {
		Siterator tmp(*this);
		--pt;
		return tmp;
	}
	T& operator*() {return *pt;}
	Siterator& operator=(const Siterator<T>& src) {
		pt=src.pt;
		return *this;
	}
 
	/*Siterator& operator=(T* _pt) {
		pt=_pt;
		return *this;
	}*/
 
	bool operator==(const Siterator<T>& src) {
		return (pt==src.pt);
	}
	/*bool operator==(T* src) {
		return (pt==src);
	}*/
	bool operator!=(const Siterator<T>& src) {
		return (pt!=src.pt);
	}
 
 
 
	bool operator<(const Siterator<T>& src) {
		return ((unsigned int)pt<(unsigned int)src.pt);
	}
 
	bool operator>=(const Siterator<T>& src) {
		return ((unsigned int)pt>=(unsigned int)src.pt);
	}
 
	bool operator<=(const Siterator<T>& src) {
		return (  (unsigned int)pt<=(unsigned int)src.pt  );
	}
 
 
	bool operator>(const Siterator<T>& src) {
		return (pt>src.pt);
	}
	operator unsigned long int() {//difference_type 변수와의 연산에서 암묵적인 타입 캐스팅
		return (unsigned long int)pt;
	}
	Siterator operator-(const Siterator& src) {
		Siterator<T> off=(T*)(pt-src.pt);
		return off;
	}
	Siterator operator+(const Siterator & src) {
		Siterator<T> tmp=(T*)(pt+(unsigned long int)src.pt);
		return tmp;
	}
	Siterator operator+(const unsigned long int offset) {
		Siterator<T> tmp(  (T*)(pt+offset)  );
		return tmp;
	}
	Siterator operator+(const int offset) {
		/*Siterator<T> tmp=(T*)(pt+offset);
		return tmp;*/
		return (T*)(pt+offset);
	}
	Siterator operator-(const unsigned long int offset) {
		Siterator tmp=(T*)(pt-offset);
		return tmp;
	}
	Siterator operator-(const int offset) {
		Siterator tmp=(T*)(pt-offset);
		return tmp;
	}
};
 
 
};
#endif
 
//test.cc
#include <iostream>
using namespace std;
#include "sdeque.h"
using namespace sstd;
int main() {
	sdeque<unsigned long int> obj1;
	//obj1.appendMemToLast(7);
	//obj1.appendMemToFirst(5);
	//obj1(1,2,3,4,5,11,12,13,14,15,16,17);
	Siterator<unsigned long int> it;
        it=&obj1[5];//여기서는 대입이 되는데요.
	if(it==&obj1[5]) {
		cout<<"The same."<<endl;
	}
	else {
		cout<<"The different."<<endl;
	}
	return 0;
}