What does `array[^1]` mean in C# compiler?

Question

        int[] numbers = new int[10];
        numbers[9] = 10;
        Console.Write(numbers[^1] == numbers[numbers.Count()-1]); //true

How does index of ^1 returns the last item in an array?

What does ^1 mean in C# compiler?

Does it have performance benefit vs numbers[numbers.Count()-1]?

Perhaps you should read the docs? https://learn.microsoft.com/en-us/dotnet/csharp/language-reference/proposals/csharp-8.0/ranges#runtime-behavior. Also, it's obviously better than using `numbers.Count()-1` since `Count()` is a Linq method that needs to iterate through the entire array. — Camilo Terevinto, Oct 26 '20 at 10:00
@CamiloTerevinto: `Enumerable.Count()` is a little smarter than that -- if applied to anything that implements `ICollection` (which includes arrays) it will just get the `.Count` of that. There's still overhead, but far less than if the whole array had to be iterated. — Jeroen Mostert, Oct 26 '20 at 10:03
@JeroenMostert I'm very aware of that, but that's an implementation detail that can change in the future :) — Camilo Terevinto, Oct 26 '20 at 10:04
Okay this is C# 8 feature, but what is equivalent code for this in C# 7? What is `^1` translated to? — Hassan Monjezi, Oct 26 '20 at 10:19

score 35 · Accepted Answer · answered Oct 26 '20 at 12:23

35

numbers[^1] is the same with numbers[length-1]

They are called ranged operators in C# 8. Check this link for more details.

answered Oct 26 '20 at 12:23

user3026017

1 Answers1