C++ : template specialization

template <>
char* Add<char*>(char* a , char* b){
return strcat(a,b);
}

char * res = Add<char*>("foo","bar");

This code refers to a new type of syntax for templates called template specialization syntax.
Generally when you write code for templates .

you end up using stuff like

template<class>

but say you want the same generic code for many cases . In the above mentioned code for example if the add function used the "+" operator to add two types it would have not worked for char* pointers , because the "+" operator does not work with them .

by using the syntax as mentioned above its possible to tell the compiler that there are exceptions to your generic code and that for special cases these new methods should be called.

C++ : The need for virtual destructors

With the advent of object oriented languages the use of polymophism became very common .
In C++ when you have a derived Class and a base class .

when you have code like this :

class Base {
};

class Derived : public Base{
};

Base * p = new Derived();

delete p;

what's wrong with it .

Since this piece of code is based on polymorphism , the base pointer will refer to an instance of a derived class object .

when delete on the pointer p is called , due to static typing in c++ , destructor of Base is called , instead of Derived . To correct this

virtual ~Base(){
}

should be added . By making the destructor virtual the destructor of the derived class would be called now .