Re: compilation error related to template parameter

"Victor Bazarov" <>
Tue, 14 Aug 2007 08:06:23 -0400
<f9s5s0$tmb$> wrote:

Consider the following program:

#include <iostream>
#include <string>
#include <vector>

using namespace std;

template<class T> class Vec : public vector<T>
Vec() : vector<T>() { }

Vec(int s) : vector<T>(s) { }

T& operator[] (int i) { return at(i); }

int main()
     Vec<string> s(3);

      return 0;

Suppose this program is named as y.cpp

When this program is compiled under Redhat Enterprise Linux
Workstation, as
g++ -std=c++98 -pedantic -Wall -Wextra y.cpp

I am getting the following compilation error:

y.cpp: In member function `T& Vec<T>::operator[](int)':
y.cpp:14: error: there are no arguments to `at' that depend on a
template parameter, so a declaration of `at' must be available

However under VC++ Express Edition 2005, it compiles well without any
warning or error.

Kindly explain what is wrong with the above program and help me in
fixing the compilation error with g++ under Linux

My newsserver is slow today, so I may be replying to something that
has already been discussed, sorry for that.

In your case 'at' is a dependent name. You need to help the compiler
to find it by pointing it to the member function. There are two ways
to do that, a 'using' declaration and an explicit qualification of
the name. So, either do

    template<class T> class Vec : public vector<T>
        using vector<T>::at;
        Vec() : vector<T>() { }

        Vec(int s) : vector<T>(s) { }

        T& operator[] (int i) { return at(i); }


    template<class T> class Vec : public vector<T>
        using vector<T>::at;
        Vec() : vector<T>() { }

        Vec(int s) : vector<T>(s) { }

        T& operator[] (int i) { return this->at(i); }
// or
// T& operator[] (int i) { return vector<T>->at(i); }

Next time read the FAQ first.

Please remove capital 'A's when replying by e-mail
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