recursive-data-structure.fsx

type FileElement =
| Folder of Name : string * Children : FileElement list
| File of {| Name:string; Size : decimal |}

let rec processFileElement element =
    match element with
    | File details ->
        printfn "Oh look, a file called %s of size %MKB!" details.Name details.Size
    | Folder (name, children) ->
        printfn "I'm entering %s. It has %d direct children." name children.Length
        for child in children do
            processFileElement child

let data =
    Folder("Media", [
        File {| Name = "Bar.txt"; Size = 5M |}
        Folder ("Music", [
            File {| Name = "ASong.mp3"; Size = 450M |}
            File {| Name = "AnotherSong.wma"; Size = 400M |}
            File {| Name = "AThirdSong.mp3"; Size = 500M |}
            Folder ("An Album", [
                File {| Name = "ANestedSong.mp3"; Size = 500M |}
            ])
        ])
        Folder ("Video", [
            File {| Name = "AVideo.avi"; Size = 4500M |}
        ])
    ])

processFileElement data
(*

I'm entering Media. It has 3 direct children.
Oh look, a file called Bar.txt of size 5KB!
I'm entering Music. It has 4 direct children.
Oh look, a file called ASong.mp3 of size 450KB!
Oh look, a file called AnotherSong.wma of size 400KB!
Oh look, a file called AThirdSong.mp3 of size 500KB!
I'm entering An Album. It has 1 direct children.
Oh look, a file called ANestedSong.mp3 of size 500KB!
I'm entering Video. It has 1 direct children.
Oh look, a file called AVideo.avi of size 4500KB!

*)