What problem does IStructuralEquatable and IStructuralComparable solve?

Question

I\'ve noticed these two interfaces, and several associated classes, have been added in .NET 4. They seem a bit superfluous to me; I\'ve read several blogs about them, but I

Answer 1

F# started using them since .net 4. ( .net 2 is here)

These interfaces are crucial to F#

let list1 = [1;5;9] 
let list2 = List.append [1;5] [9]

printfn "are they equal? %b" (list1 = list2)

list1.GetType().GetInterfaces().Dump()