SFINAE and enable_if<>

See:

• Template SFINAE & type-traits (very good)

• Filipek: Notes on C++ SFINAE

• Filipek: SFINAE Followup

• SFINAE and enable_if (very good)

• Modern C++, Item 27 by Scott Meyers

• Microsoft enable_if Article has Several Examples

Type alias, alias template

The keyword using is a another way of creating a typedef, an alias of a type.

template<typename T> class Vector {

  public:
    using value_type = T; // Same as: typedef T value_type;
    //...
};

Vector<int> v;
Vector<int>::value_type x = 10; // x is of type int.

using value_type = T; is equivalent to typedef T  value_type;. There is also a form of using for use with templates. It can help to create, for example, more readable templates.

template<class T> struct Alloc {
      //...
};

template<class T> using Vec = vector<T, Alloc<T>>; // type-id is vector<T, Alloc<T>>

Vec<int> v; // Vec<int> is the same as vector<int, Alloc<int>>

Vec is an alias template, and Vec<int> results in substituting int for T in template<typename T> vector<T, Alloc<T>>. Thus, Vec<int> is just an alias for vector<T, Alloc<T>>.

Todo

Finish later.