template specialization implementation - c++

Question

I have to implement template specialization, in implementing the constructor for specialized template class compiler generates some errors. Following is my code:
#include <iostream>
using namespace std;
// class template
template <typename T>
class mycontainer
{
T element;
public:
mycontainer (T arg);
T increase () {return ++element;}
};
// class template specialization
template <>
class mycontainer <void> {
int element;
public:
mycontainer (int arg);
char uppercase ()
{
return element;
}
};
template<typename T> mycontainer<T>::mycontainer(T arg){
cout << "hello T" << endl;
}
template<typename T> mycontainer<void>::mycontainer(int arg){
cout << "hello Empty" << endl;
}
int main () {
mycontainer<int> myint (7);
mycontainer<void> myvoid (6);
cout << myint.increase() << endl;
return 0;
}
The code generate these errors:
test.cpp:31:22: error: prototype for ‘mycontainer<void>::mycontainer(int)’ does not match any in class ‘mycontainer<void>’
test.cpp:16:26: error: candidates are: mycontainer<void>::mycontainer(const mycontainer<void>&)
test.cpp:19:5: error: mycontainer<void>::mycontainer(int)
Any clue on how to resolve these errors ?

Answer 1

Your syntax for full specialization is wrong, you SHOULDN'T use template<typename T> mycontainer<void> or not even template<>
Why? See quote from C++ template book:
A full specialization declaration is identical to a normal class declaration in this way (it is not a template declaration). The only differences are the syntax and the fact that the declaration must match a previous template declaration. Because it is not a template declaration, the members of a full class template specialization can be defined using the ordinary out-of-class member definition syntax (in other words, the template<> prefix cannot be specified):
So can either do
mycontainer<void>::mycontainer(int arg){
cout << "hello Empty" << endl;
}
or do:
#include <iostream>
using namespace std;
// class template
template <typename T>
class mycontainer
{
T element;
public:
mycontainer<T>::mycontainer(T arg)
{
cout << "hello T" << endl;
}
T increase () {return ++element;}
};
// class template specialization
template <>
class mycontainer <void> {
int element;
public:
mycontainer (int arg)
{
cout << "hello Empty" << endl;
}
char uppercase ()
{
return element;
}
};
int main () {
mycontainer<int> myint (7);
mycontainer<void> myvoid (6);
cout << myint.increase() << endl;
return 0;
}

Answer 2

mycontainer<void> is not a template, and neither is its constructor, so the constructor definition should just be:
mycontainer<void>::mycontainer(int arg){
cout << "hello Empty" << endl;
}

Answer 3

Your prototype
template<typename T> mycontainer<void>::mycontainer(int arg){
cout << "hello Empty" << endl;
}
does not match the one in the specialization. Leave the template parameter empty.
That being said: Your C++ does not look like you are ready for using templates. You should get the basics right first.