// Learn more about F# at http://fsharp.org

open System


type instruction =
   | ADD (* dodawanie *)
   | SUB (* odejmowanie *)
   | MUL (* mnozenie *)
   | SQR (* podnoszenie do kwadratu *)
   | PUSH of float (* odkladanie na stos *)
   | DIV

type Stack = float list
exception WrongProgramException of (instruction * Stack)
exception ErrException of (Stack)
exception ErException

let intInstr (x , y) =
   match x , y with
   | ADD, a::b::ys -> (b + a) :: ys : Stack
   | SUB, a::b::ys -> (b - a) :: ys
   | MUL, a::b::ys -> (b * a) :: ys
   | SQR, a::ys -> (a * a) :: ys
   | PUSH x, ys -> x::ys
   | DIV, a::b::ys -> try
                          Some (b / a) :: ys
                      with
                           | :? System.DivideByZeroException -> printfn "Division by zero!";
   | _, _ -> raise ErException;

let wypisz_instr = function
    | ( PUSH x) -> "PUSH " + System.Convert.ToString(x)
    | ( SQR ) -> " SQR "
    | ( ADD ) -> " ADD "
    | ( SUB ) -> " SUB "
    | ( MUL ) -> " MUL "
    | ( DIV ) -> " DIV "

let rec wypisz is =
    match is with
    | x::is -> printfn "%A" (wypisz_instr x); wypisz(is)
    | _ -> []

let intpProg(is) =
    let rec iPS = function
    | ([],x::xs) -> x
    | (i::is, xs) -> try
                         iPS(is, intInstr(i, xs))
                     with
                         ErException -> ( wypisz(is); 0.0 )
    | _ -> 0.0
    iPS(is,[]) (* start programu, stos początkowo pusty *)


[<EntryPoint>]
let main argv =
    // WPROWADZENIE
    let i1 = PUSH 3.0
    let i2 = PUSH 4.0
    let i3 = ADD
    let stos:Stack = []    (* lista pusta musi być określonego typu *)
    let stos1 =  intInstr(i1,stos)
    let stos2 =  intInstr(i2,stos1)
    let stos3 =  intInstr(i3,stos2)

    // printfn "%A" stos3

    let il1 = [PUSH 3.0; PUSH 4.0; ADD; PUSH 2.0; MUL; MUL; MUL; MUL]
    let w = intpProg(il1)
    printfn "%A" w


    let il2 = [PUSH 4.0; PUSH 0.0; DIV]
    let w = intpProg(il2)
    printfn "%A" w






    0 // return an integer exit code