template inheritance in c++

Base.hpp

template<typename T>
class Base
{
public:
    T someVariable;
};

der1.cpp

#include "Base.hpp"

// the only right way of inheriting template to template 

template<typename T>
class Der : public Base<T>
{};

der2.cpp

#include "Base.hpp"

// invalid way of inheritence

template<typename T>
class Der<T> : public Base // this line must be `class Der : public Base<T>`
{};

der3.cpp

#include "Base.hpp"

// if you want to make specilization of the class, you MUST inherit first then type the specilization

// usual iheritence
template<typename T>
class Der : public Base<T>
{};

// specilization
template<>
class Der<int> : public Base<int>
{};

der4.cpp

#include "Base.hpp"

// invalid

class Der : public Base
{};

der5.cpp

#include "Base.hpp"

// valid, you are inheriting class to class

class Der : public Base<int>
{};

der6.cpp

#include "Base.hpp"

// valid, Der is template class that inherits from Base<int>

template<class T>
class Der : public Base<int>
{};

// invalid, you cant inherit this way

template<typename T>
class Der<T> : public Base<int>
{};

Makefile

# if you want to run the examples and check them on your terminal
# type make 

run_all: *.cpp
	g++ -std=c++11 *.cpp -c 

clean:
	rm *.o

SUMMARY.md

inherit (template to template):

template<typename T>

class Der : public Base<T>

Der is now a template class that iherits from Base

specialize Der

you must inherit it as template first then make the specilzation

template<typename T>

class Der : public Base<T>

...

template<>

class Der<int> : public Base<int>

Der is now a template class and has its own int specilization

inherit (class to template)

template<typename T>

class Der : public Base<int>

inherit (class to class)

class Der : public Base<int>

Der is a class, NOT template class.