Re: template template parameters not working with STL containers

From:
"Bo Persson" <bop@gmb.dk>
Newsgroups:
comp.lang.c++.moderated
Date:
Thu, 19 Feb 2009 01:09:18 CST
Message-ID:
<70300uFmmvj8U1@mid.individual.net>
vl106 wrote:

The code sample below is not working. It is taken from
Nicolai Josuttis "C++ Templates: The Complete Guide".
In the chapter 5.4 Template Template Parameters it reads
[slightly stripped]:

#include <deque>

template <typename T>
class MyVector {
public:
void push_back(T const&) {}
};

template <typename T, template <typename> class CONT = /*MyVector*/
std::deque >
class Stack {
private:
    CONT<T> elems; // elements
  public:
    void push(T const&); // push element
};

With Visual Studio 2005 I get the following error message:

 error C3201: the template parameter list for class template
'std::deque' does not match the template parameter list for template
parameter 'CONT'
 error C3201: the template parameter list for class template
'std::deque' does not match the template parameter list for template
parameter 'CONT'
 error C2976: 'std::deque' : too few template arguments
 deque(486) : see declaration of 'std::deque'

The problems is not the template template parameter itself.
When I substitute the default argument with "MyVector" the
code compiles fine.

How do I have to modify the sample to make it work with the
original STL containers std::deque, std::vector, ...


The error messages actually tells you what the problem is:

The problem is that std::deque and std::vector also has additional
default template arguments. You require a template with a single
argument, so the standard containters do not match.

Bo Persson

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