Why can std::get() not be used to get members of a vector?

Question

I am confused about the std::get() function. std::get() can be used to access members in array, pair, and tuple. So, why does the Standard not also allow it to access the members in vector?

#include <iostream> #include <array> #include <vector> #include <tuple> #include <utility> // std::pair using namespace std; int main() {     array<int, 4> a1{3,4,5,67};     pair<int,int>  p1{5,6};     tuple<int,float,float> t1{6,5.5,4.5};      cout << std::get<1>(a1) <<endl;     cout << std::get<1>(p1) <<endl;     cout << std::get<1>(t1) <<endl; } 

Following is the output:

4 6 5.5 

But when I try to use std::get() with vector, I get this compilation error:

#include <iostream> #include <array> #include <vector> #include <tuple> #include <utility> // std::pair using namespace std; int main() {  vector<int> v1{4,5,6,7,9};  cout << std::get<1>(v1) <<endl; } 

Compilation error:

  main.cpp: In function 'int main()':   main.cpp:10:27: error: no matching function for call to 'get(std::vector&)'   cout << std::get<1>(v1) <<endl;                        ^   In file included from main.cpp:2:0:  /usr/include/c++/5/array:280:5: note: candidate: template constexpr _Tp&    std::get(std::array<_Tp, _Nm>&)   get(array<_Tp, _Nm>& __arr) noexcept   ^