How to define a type extension for T[] in F#?

Question

In C#, I can define an extension method for a generic array of type T like this:

public static T GetOrDefault(this T[] arr, int n)
{
    if (arr.Len         


        

Answer 1

Good question. I can't figure out how to extend 'T[] but you can take advantage of the fact that arrays implement IList<_> to do:

type System.Collections.Generic.IList<'T> with
  member x.GetOrDefault(n) = 
    if x.Count > n then x.[n]
    else Unchecked.defaultof<'T>

let arr = [|1; 2; 3|]
arr.GetOrDefault(1) //2
arr.GetOrDefault(4) //0