ppx_deriving

Hi there,
I tried a minimal example like this:

<-----------------snip----------------->
open Ppx_deriving
open Ppx_deriving_runtime

type blatype = A | B
  [@@deriving show]

let _ =
  Printf.printf "%s\n" (show_blatype A);
<-----------------snap----------------->

using ocamlfind to compile and link it like this:

ocamlfind ocamlopt -package ppx_deriving.show showtest.ml -o showtest

getting:

File "showtest.ml", line 5, characters 0-40:
Error: Unbound type constructor Format.formatter

I have no idea how to resolve this (I read the documentation at
https://github.com/whitequark/ppx_deriving but was not able to find the
solution there).

Any help appreciated.


Thanks, Manfred