open System
open System.IO
//1
type formatText=
    | Simplestr of string
    | Bullet_item of List<formatText>
    | Bold_text of formatText
    | Italic_text of formatText
    | Headers of formatText

//2
let rec render formatText =
    match formatText with
    | Simplestr(x) -> printf "%s" x
    | Bullet_item(x) -> List.iter(fun elem -> printf "</> %s" "";render(elem);printf "\n") x
    | Bold_text(x) -> printf "<B> %s" ""; render(x)
    | Italic_text(x) -> printf "<I> %s" ""; render(x)
    | Headers(x) -> printf "<H> %s" ""; render(x)

let example = Bullet_item([Bold_text(Simplestr("1TEST"));Simplestr("2TEST");Italic_text(Simplestr("3TEST"));Bullet_item([Simplestr("111TEST");Simplestr("222TEST");Simplestr("333TEST")])])

render(example)
render(Headers(Italic_text(Bold_text(Simplestr("nsd")))))
 //3
///////////////////////////////////////
let rec min = function
| [] -> failwith("error")
| [x] -> (x,[])
| h::t ->
    let (x1,y1) = min t
    if h<x1 then (h,t)
    else (x1,h::y1)

min [2;3;1;3]


let rec sort = function
| [] -> []
| S ->
    let (x1,y1)= min S
    (x1::(sort y1))


sort [2;3;1;3]



let rec F =function
| [] -> []
| h::t ->h:: F(List.filter (fun x->x%h<>0) t)

F [2..100]


let Flength =
    let rec len a = function
    | [] -> a
    | _::t -> len (a+1) t in len 0

[1;2;34;32;1;23;1;0;2]
|> List.sort

List.groupBy(fun x->x%3) [1;2;3;4;5;6;7;8;9]