الأنواع المخصّصة الداعمة للنطاقات

using System;

class Deck {
    private int[] cards = { 1, 2, 3, 4, 5 };
    public int this[Index i] => cards[i];
}

var d = new Deck();
Console.WriteLine(d[^1]); // 5

using System;

class Deck {
    private int[] cards = { 1, 2, 3, 4, 5 };
    public int[] this[Range r] => cards[r];
}

var d = new Deck();
Console.WriteLine(string.Join(",", d[1..3])); // 2,3

using System;

class Buffer {
    private int[] data = { 10, 20, 30, 40 };
    public int Length => data.Length;
    public int this[int i] => data[i];
    public int[] Slice(int start, int length) {
        var result = new int[length];
        Array.Copy(data, start, result, 0, length);
        return result;
    }
}

var buf = new Buffer();
Console.WriteLine(string.Join(",", buf[1..3])); // 20,30

using System;

class Buffer {
    private int[] data = { 10, 20, 30, 40 };
    public int Length => data.Length;
    public int this[Index i] => data[i.GetOffset(Length)];
}

var buf = new Buffer();
Console.WriteLine(buf[^1]); // 40

using System;

class Ring {
    private string[] items = { "a", "b", "c" };
    public int Length => items.Length;
    public string this[Index i] {
        get {
            int offset = i.GetOffset(Length);
            return items[offset];
        }
    }
}

var r = new Ring();
Console.WriteLine(r[^2]); // b

using System;

class Ring {
    private int[] items = { 1, 2, 3, 4, 5 };
    public int Length => items.Length;
    public int[] this[Range r] {
        get {
            var (start, len) = r.GetOffsetAndLength(Length);
            var slice = new int[len];
            Array.Copy(items, start, slice, 0, len);
            return slice;
        }
    }
}

var r = new Ring();
Console.WriteLine(string.Join(",", r[^3..^1])); // 3,4

using System;
using System.Collections.Generic;

var list = new List<int> { 1, 2, 3, 4 };
// List<T> has Count, so Index works:
Console.WriteLine(list[^1]); // 4

using System;

class Sequence {
    private int[] data;
    public Sequence(int[] d) => data = d;
    public int Length => data.Length;
    public int this[Index i] => data[i];
    public int[] this[Range r] => data[r];
}

var s = new Sequence(new[] { 5, 10, 15, 20 });
Console.WriteLine(s[^1]);                       // 20
Console.WriteLine(string.Join(",", s[1..^1]));  // 10,15