template specialization vs template instantination

[stmfc]

what is the difference between
template specialization vs template instantination in C++ ?

thanks in advance...

[OuaisBla]

template instanciation is when you give a to a template class a template parameter.

Like:

std::vector<string> v;

v is an instanciation of a template.

Specialization is more complex but let me try to explain it simply.

template<class T>
class vector { };  //base template

template<class T>
class vector<T *>   //partial specialization
{ };

template<>
class vector<string>   //complete specialization
{ };

The compiler will choose each implentation is the better one regarding the template paramameters. Each specialization is a complete distinct class from the the base template. But this allows optimization and/or custom behaviour regarding different type using the same syntax.

vector<int> vi; //defaut template is used
vector<int *> vip; //vector<T*> is used
vector<string> vs; //vector<string> is used

this offers lots of room for optimization, but for a vector user it is always a vector that is used.

I hope this helps.