template template argument - type/value mismatch error

c++, class, templates

Solution

`'template<class> class Stack', got 'template<class _Tp, class _Sequence> class std::stack'` shows the problem.

Here is what `std::stack` looks like

template<
    class T,
    class Container = std::deque<T>
> class stack;

As you can see there is a second parameter.

Adding:

#include <deque>
template <std::size_t N,
         template <class T, class = std::deque<T>> class Stack = std::stack
         >

should make it compile.

Problem

Here's a sample code: ``` #include <stack> #include <cstddef> template <std::size_t N, template <class> class Stack = std::stack > class Tower : protected Stack<int> { public: Tower() : Stack<int>(N) { } }; int main(int argc, char **argv) { Tower<5L> tower1(); } ``` And I see the compiler (gcc) is not happy: ``` file.cpp: In function 'int main(int, char**)': file.cpp:18:11: error: type/value mismatch at argument 2 in template parameter list for 'template<long unsigned int N, template<class> class Stack> class Tower' file.cpp:18:11: error: expected a template of type 'template<class> class Stack', got 'template<class _Tp, class _Sequence> class std::stack' file.cpp:18:21: error: invalid type in declaration before ';' token ``` The standard stack container has this form: `template <class Type, class Container = deque<Type> > class stack`; Meaning I should be fine to pass only one template argument here! Any thoughts on how to resolve this? Thanks

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