Enumerated Classes

Question

I came up with the following pattern and wondered if there was a name for it?

An enumdefines specific classes:

enum Fruits{ eApple, eBanana };

And the template structprovides an interface:

template< Fruit T >
struct SomeFruit {
    void eatIt() { // assert failure };
};

Then we can implement specific classes:

template<>
struct SomeFruit< eApple > {
    void eatIt() { // eat an apple };
};

template<>
struct SomeFruit< eBanana > {
    void eatIt() { // eat a banana };
};

And use them this way:

SomeFruit< eApple> apple;
apple.eatIt();

Answer 1

This is commonly used like this (to catch errors at compile time)

template< Fruit T >
struct SomeFruit;

template<>
struct SomeFruit< eApple > {
    void eatIt() { // eat an apple };
};

template<>
struct SomeFruit< eBanana > {
    void eatIt() { // eat a banana };
};

and is often called compile-time polymorphism (as opposed to run-time polymorphism, which in C ++ is achieved using virtual functions).

Answer 2

, - , , - :

template< Fruit T >
struct SomeFruit;

Answer 3

This is called specialized specialization. In this case, this is a clear (aka full) specialization, which is recognized template <>, in contrast to partial specialization.