Instantiation

Considering the class template, V, we defined in the previous section, we'll assume the following declarations appear later:

V<char> cV;
V<int>  iV(10);
V<float> fV(5);

Then, the compiler will create three instances of the V class, as follows:

class V<char>{
public:
  V(int n=0);
 // ...
public:
  int  m_nEle;
  char *m_buf;
};

class V<int>{
public:
  V(int n=0);
 // ...
public:
  int  m_nEle;
  int *m_buf;
};

class V<float>{
public:
  V(int n = 0);
  // ...
public:
  int   m_nEle;
  float *m_buf;
};

Similar to function template instantiation, there are two forms of class template instantiation – explicit instantiation and implicit instantiation. Let's take a look at them.