static string GetRecursiveText(int verse)
{
if (verse == 1)
{
return("");
}
string recString = GetRecursiveText(verse - 1);
if (verse == 2)
{
return($"wriggled and jiggled and tickled inside her.\n" +
"She swallowed the spider to catch the fly.\n");
}
else
{
return($"She swallowed the {GetAnimal(verse)} to catch the {GetAnimal(verse-1)}{(verse==3 ? " that " : ".\n")}{recString}");
}
}
static void Main(string[] args)
{
Console.WriteLine("逆变和协变");
// 数组的协变
Animal[] dogs = new Dog[] {};
// 委托协变
GetAnimal getAnimal = new GetAnimal(GetDog);
getAnimal();
// 委托逆变
FeedDog feedDog = FeedAnimal;
feedDog(new Dog());
// 委托泛型逆变
Feed <Animal> feedAnimalMethod = a => Console.WriteLine("Feed Animal Lambda!");
Feed <Dog> feedDogMethod = feedAnimalMethod;
feedDogMethod(new Dog());
Find <Dog> findDog = () =>
{
Console.WriteLine("Find Dog!!");
return(new Dog());
};
Find <Animal> findAnimal = findDog;
findAnimal();
// 接口逆变
IFeedable <Dog> feedDog2 = new FeedImp <Animal>();
feedDog2.Feed(new Dog());
// 接口协变
IFinder <Animal> findAnimal2 = new Finder <Dog>();
//============
Console.ReadLine();
}
