public static void Main(string[] args)
{
// Suppose I have a few collections of animals.
Iguana[] igs = new Iguana[] { new Iguana() };
Rat[] rats = new Rat[] { new Rat() };
Animal[] animals = new Animal[] { new Iguana(), new Rat() };
// Which of these function calls is valid?
/*
* PrintAnimal(igs[0]);
* PrintAnimal(animals[0]);
* PrintIguana(animals[0]);
* PrintRat(igs[0]);
* PrintRat(rats[0]);
*
* Why??
*/
// How about these?
/*
* PrintAnimals(animals);
* PrintAnimals(igs);
* PrintAnimals(rats);
* PrintRats(rats);
* PrintRats(animals);
*
* Why??
*/
}
public static void Main(string[] args)
{
// Suppose I have a few collections of animals.
Iguana[] igs = new Iguana[] { new Iguana() };
Rat[] rats = new Rat[] { new Rat() };
Animal[] animals = new Animal[] { new Iguana(), new Rat() };
// Which of these function calls is valid?
/*
* PrintAnimal(igs[0]);
* PrintAnimal(animals[0]);
* PrintIguana(animals[0]);
* PrintRat(igs[0]);
* PrintRat(rats[0]);
*
* Why??
*/
// How about these?
/*
* PrintAnimals(animals);
* PrintAnimals(igs);
* PrintAnimals(rats);
* PrintRats(rats);
* PrintRats(animals);
*
* Why??
*/
/* And these???
* Action<Animal> a2 = PrintAnimal;
* Action<Rat> a2 = PrintRat;
*
* Action<Iguana> a1 = PrintAnimal;
* Action<Rat> a1 = PrintAnimal;
* Action<Animal> a2 = PrintRat;
*/
/* Or THESE???
* Func<Rat> f1 = CreateRat;
* Func<Iguana> f2 = CreateRat;
* Func<Animal> f3 = CreateRat;
*
*/
// CONCLUSIONS:
// A collection can be covariant if it is ____________________.
// A collection can be contravariant if it is ____________________.
// A function pointer/delegate can be covariant in its ________________.
// A function pointer/delegate can be contravariant in its ________________.
}
public static void PrintIguana(Iguana a)
{
Console.WriteLine(a.Speak());
}
