Return a random string from an array of strings

ReturnRandomString.fs

// Copy/paste this into the FSI to see what it does. 
open System

let a = [|"a";"b";"c";"d"|]

let randstring (arr:string[]) =
   let r = new Random()
   arr.[r.Next(arr.Length)]

let resultstring = randstring a;;

//And a variant: if the string is inside of the function, you need to declare 
//slightly differently to get things to work correctly.
//Note the unit parameter to the function.  

let randstring_i() =
   let str_arr = [|"a";"b";"c";"d"|]
   let r = new Random()
   str_arr.[r.Next(str_arr.Length)]

let resultstring2 = randstring_i();;