Put a timeout on executions

[cartermp]

The following code contains an infinite loop in it:

open System

type Ops = Add | Sub | Mul | Div | And | Or | Eor | Bic | Lsl | Lsr | Asr | Ror | Ldc of int
         | Dup | Drop | Swap | Over | Ld8 | St8 | Ld16 | St16 | Ld32 | St32 | Se8 | Se16
         | For of Exp | Next | If of Exp*Exp | Func of string*Exp | Ldl of string | Stl of string
and Exp = Ops list

type Sym = Var of int32 | Fun of Exp

let symbols = Map.empty

let isNumber (x:string) = fst (Int32.TryParse(x))


let getOps = function
    | "+" -> Add
    | "-" -> Sub
    | "*" -> Mul
    | "/" -> Div
    | "and" -> And
    | "or" -> Or
    | "eor" -> Eor
    | "bic" -> Bic
    | "lsl" -> Lsl
    | "lsr" -> Lsr
    | "asr" -> Asr
    | "ror" -> Ror
    | "dup" -> Dup
    | "drop" -> Drop
    | "swap" -> Swap
    | "over" -> Over
    | "ld8" -> Ld8
    | "st8" -> St8
    | "ld16" -> Ld16
    | "st16" -> St16
    | "ld32" -> Ld32
    | "st32" -> St32
    | "for" -> For []
    | "next" -> Next
    | x when isNumber x -> Ldc (int x)
    | x -> failwithf "Unknown word %A" x

let exec = function
    | (Add,x::y::xs) -> (x+y)::xs
    | (Sub,x::y::xs) -> (y-x)::xs
    | (Mul,x::y::xs) -> (x*y)::xs
    | (Div,x::y::xs) -> (y/x)::xs
    | (Ldc x,xs)     -> x::xs
    | (_,[]) -> failwith "Empty stack"
    | x      -> failwithf "Unknown Op %A" x

let infix = function
    | (Add,x::y::xs) -> ("("+x+" + "+y+")")::xs
    | (Sub,x::y::xs) -> ("("+y+" - "+x+")")::xs
    | (Mul,x::y::xs) -> ("("+x+" * "+y+")")::xs
    | (Div,x::y::xs) -> ("("+y+" / "+x+")")::xs
    | (Ldc x,xs)     -> (string x)::xs
    | (_,[]) -> failwith "Empty stack"
    | x      -> failwithf "Unknown Op %A" x

let run f = Array.fold (fun xs op -> f (op,xs)) []

//let source = "2 3 + 1 - 2 /"
let source = "1 4 for dup + next + -"
let code = source.Split() |> Array.filter ((<>)"") |> Array.map getOps

printfn "Source:  %A" source
printfn "Code:    %A" code

let rec combFor xs bb ys depth =
    match xs with
    | [] -> if bb <> [] then printfn "ERROR: bb not empty %A" bb
            (xs,[],List.rev (bb@ys))
    | Next::xs when depth = 0 -> printfn "ERROR: No For!"
                                 failwith ""
    | Next::xs when depth = 1 -> (xs,[],List.rev (bb@ys))//(xs,List.rev bb,ys)
    //| Next::xs when depth > 0 -> combFor xs bb ys (depth - 1)
    //| For [] :: xs -> combFor xs bb (For []::ys) (depth + 1)
    | For [] :: xs   -> let (xs,bb,ys) = combFor xs bb ys (depth + 1)
                        combFor xs [] (For bb :: ys) (depth + 1)
    | x::xs when depth > 0 -> combFor xs (x::bb) ys depth
    | x::xs -> combFor (x::xs) bb ys depth

let c = List.ofArray code
printfn "Code:    %A" c
let d = combFor c [] [] 0 
printfn "CFor:    %A" d

//printfn "Infix:   %A" (run infix code)
//let result = run exec code
//printfn "Result = %A" (List.rev result)

It's a lot, but this will run infinitely on a local machine as a console app.

In the browser, this will freeze the page until your browser eventually asks to quit. We should put a limit on execution time and stop executing code, then notify the user about that.