OVerloaded function calling issue - c++

Question

I have 2 overloaded function say - func1 and func2 -
Func1 is -
template<typename T1, typename T2> bool AreIdentical(const std::pair<T1, T2>
&lhs, const std::pair<T1, T2> &rhs)
{
//some code
}
Func2 is -
template<typename T> bool AreIdentical(typename std::map<int,
std::vector<T>>::iterator itOrig,
typename std::map<int, std::vector<T>>::iterator itNew)
{
//some code
}
I am trying to call the function AreIdentical in below manner -
int main()
{
std::map<int, std::vector<int>> orgitem;
std::map<int, std::vector<int>> newitem;
newitem[0];
orgitem[0];
AreIdentical(*orgitem.begin(), *newitem.begin());
return 0;
}
Now, interesting thing is, my origitem and newitem is of map type but always Func1 is getting called which takes parameter pair type instead of Func2.
Do anyone have any clue why is it happening so?

Answer 1

orgitem.begin() is an iterator. But *orgitem.begin() is the object the iterator points at, which is a std::pair<const int, std::vector<int>>.
If you had
AreIdentical(orgitem.begin(), newitem.begin());
without the dereferencing * operators, that would not be able to call the pair overload.
But in fact it won't work either, because in your second overload the parameter T is not in a deducible context. The only way to call it is:
AreIdentical<int>(orgitem.begin(), newitem.begin());
You might be able to "fix" this by changing the iterator overload to just accept any iterator whose value type has members first and second:
template <typename Iter>
auto AreIdentical(Iter itOrig, Iter itNew)
-> decltype((*itOrig).first, (*itOrig).second, bool{});