static void Main(string[] args)
{
// Listing 3.2 Constructing BCL immutable collections
var list = ImmutableList.Create <int>(); //#A
list = list.Add(1); //#B
list = list.Add(2);
list = list.Add(3);
var builder = ImmutableList.CreateBuilder <int>(); //#C
builder.Add(1); //#D
builder.Add(2);
builder.Add(3);
list = builder.ToImmutable(); //#E
// Listing 3.14 A functional list in C#
FList <int> list1 = FList <int> .Empty;
FList <int> list2 = list1.Cons(1).Cons(2).Cons(3);
FList <int> list3 = FList <int> .Cons(1, FList <int> .Empty);
FList <int> list4 = list2.Cons(2).Cons(3);
Demo.PrintSeparator();
Console.WriteLine("Listing 3.15 Lazy list implementation");
var lazyList1 =
new LazyList <int>(42, new Lazy <LazyList <int> >(() =>
new LazyList <int>(21, LazyList <int> .Empty)));
var lazyList =
lazyList1.Append(
new LazyList <int>(3, LazyList <int> .Empty));
lazyList.Iterate(Console.WriteLine);
Demo.PrintSeparator();
Console.WriteLine("Listing 3.16 Immutable B-tree representation");
var tree =
new BinaryTree <int>(20,
new BinaryTree <int>(9,
new BinaryTree <int>(4,
new BinaryTree <int>(2, null, null),
null),
new BinaryTree <int>(10, null, null)),
null);
var exist9 = tree.Contains(9);
Console.WriteLine($"Tree contains 9 : {exist9}");
var tree21 = tree.Insert(21);
var exist21 = tree21.Contains(21);
Console.WriteLine($"Tree21 contains 21 : {exist21}\n");
tree.InOrder(Console.WriteLine);
Console.ReadLine();
}
public static FList <T> Where <T>
(this FList <T> list, Func <T, bool> predicate)
{
if (list.IsEmpty)
{
return(list);
}
var newTail = list.Tail.Where(predicate);
return(predicate(list.Head)
? newTail.Cons(list.Head)
: newTail);
}
public FList <T> Cons(T element) //#G
{
return(FList <T> .Cons(element, this));
}
} //#E
public static FList <T> Cons(T head, FList <T> tail) //#F
{
return(tail.IsEmpty
? new FList <T>(head, Empty)
: new FList <T>(head, tail));
}