Is there a more sensible way to convert an int to a string in Cameligo?

Question

Is there a more sensible way to convert an int to a string in Cameligo?

Alternatively, is there a way to concatenate an int or nat with a string?

type lookup = (int, string) map
let lookup: lookup = Map.literal[(0, "0"); (1, "1"); (2, "2"); (3, "3"); (4, "4"); (5, "5"); (6, "6"); (7, "7"); (8, "8"); (9, "9")]

let digitToStr (key: int): string =
  match Map.find_opt key lookup with
    Some str -> str
  | None -> (failwith "Not found": string)

let rec intToStr ((x, str): int * string) : string =
    if (x < 10) then 
      digitToStr(x) ^ str 
    else
      intToStr((
        x / 10, 
        digitToStr(int(x mod 10)) ^ str
      ))

let main (x: int) : string =
    intToStr((x, ""))