operator overloading c++ (x==y==z) - c++

Question

I have encountered a strange problem, that I don't know how to solve in overloading.
Im trying too overload operator == .
The easy example would be:
class bla{
public:
int a;
void bla(int a):a(a){}//costructor
bool operator==(const bla& ob)
return (a==ob.a);//chk if equal
};
void main(){
bla A,B;
if (A==B)
flag=1;//just an example...
this is easy and works great, i'm trying to handle the case of:
if (A==B==C==D)
so i need to return type object and now type bool.
i have tried to add another function :
bla &bla:: operator==(const bool answer){//as a member function
if (answer)
return *this;
but it doesn't seem to help. have any suggestions?
thx Stas

Answer 1

This is a horrible idea and you should never do it.
Here is how you do it.
#include <type_traits>
template<typename T, typename U>
struct decay_equiv
: std::is_same<
typename std::decay<T>::type,
typename std::decay<U>::type
>::type {};
template<typename T>
struct comparator {
bool res;
T passalong;
explicit operator bool() { return res; }
typename std::enable_if<
!decay_equiv<T, comparator<T> >::value,
comparator<T>
>::type operator==(T const& rhs);
comparator<T> operator==(comparator<T> const& rhs);
};
template<typename T>
typename std::enable_if<
!decay_equiv<T, comparator<T>>::value,
comparator<T>
>::type comparator<T>::operator==(T const& rhs) {
if (!res) {
return {res, rhs};
}
return {(passalong == rhs).res, rhs};
}
template<typename T>
comparator<T> comparator<T>::operator==(comparator<T> const& rhs) {
if (!res || !rhs.res) {
return {res, rhs};
}
return {(passalong == rhs.passalong).res, rhs.passalong};
}
struct bla {
int a;
comparator<bla> operator==(bla const& rhs);
comparator<bla> operator==(comparator<bla> const& rhs);
};
comparator<bla> bla::operator==(bla const& rhs) {
return {a == rhs.a, rhs};
}
comparator<bla> bla::operator==(comparator<bla> const& rhs) {
if (!rhs.res) {
return rhs;
}
return {a == rhs.passalong.a, rhs.passalong};
}
int main() {
bla a = {0},b = {0},d = {0};
if (a==b==d)
return 0;
return -1;
}
This code assumes C++11, but can be written in C++98 with only very minor changes.

Answer 2

i have managed to find a different approach and it seems to work great.
thx to u all for your help and suggestions.
class bla{
public:
int a;
bool f;
void bla(int a):a(a){f = true;}//costructor
operator bool(){return f};
bla& operator==(const bla &ob){//chk if equal
if (f)
f=(a==ob.a);
return *this;
}
};
void main(){
bla A(4),B(4),C(4),D(4);
if (A==B==C==D)
flag=1;//just an example...