Re: Redefintion of a function in template class

I'd like to ask the reason the following code works. Original, I
expected that there is going to be a "function redefinition" error.
Could anyone tell me whether this is a compiler specific (I am using
GNU g++ 4.3.4) issue or this actually conforms to the C++ standard? I
appreciate.

A function f is defined in a template class A. Class B inherited from
A<int> redefines the function f in A<int>. The output shows that the
definition f in A<int> is actually changed, while the other instance
of the template, e.g. A<float>, remains untouched.

//===================================
#include<iostream>

template<class T>
class A
{
public:

     typedef A<T> BaseT;
     int f();
};

template<class T>
int A<T>::f()
{
     return 1;
}

class B : public A<int>
{
};

template<>
int
B::BaseT::f()
{
     return 3;
}

int main()
{
     A<int> a1;
     A<float> a2;
     B b;
     std::cout<< a1.f()<< std::endl;
     std::cout<< a2.f()<< std::endl;
     std::cout<< b.f()<< std::endl;
}

// ======================================
// The output of the program is
// 3
// 1
// 3