//http://www.fssnip.net/an

// Problem 8 : Eliminate consecutive duplicates of list elements.

/// If a list contains repeated elements they should be replaced with a single copy of the

/// element. The order of the elements should not be changed.

///

/// Example:

/// * (compress '(a a a a b c c a a d e e e e))

/// (A B C A D E)

///

/// Example in F#:

///

/// > compress ["a";"a";"a";"a";"b";"c";"c";"a";"a";"d";"e";"e";"e";"e"];;

/// val it : string list = ["a";"b";"c";"a";"d";"e"]

let compress list =

let foldBacker item acc =

//printfn "acc %A item %A" acc item

match acc with

| [] -> [item]

| h::_ when h = item -> acc

| h::_ when h <> item -> item::acc

List.foldBack foldBacker (List.rev list) [] |> List.rev

compress ["a";"a";"a";"a";"b";"c";"c";"a";"a";"d";"e";"e";"e";"e"] |> printfn "%A";;

/// val it : string list = ["a";"b";"c";"a";"d";"e"]