$ ocaml
        OCaml version 4.02.0

# #use "topfind" ;;
- : unit = ()
Findlib has been successfully loaded. Additional directives:
  #require "package";;      to load a package
  #list;;                   to list the available packages
  #camlp4o;;                to load camlp4 (standard syntax)
  #camlp4r;;                to load camlp4 (revised syntax)
  #predicates "p,q,...";;   to set these predicates
  Topfind.reset();;         to force that packages will be reloaded
  #thread;;                 to enable threads

- : unit = ()
# #require "ppx_deriving" ;;
/home/kaustuv/.opam/4.02.0/lib/ppx_deriving: added to search path
/home/kaustuv/.opam/4.02.0/lib/ppx_deriving/./ppx_deriving: activated
# type t = [`A | `B] [@@deriving show] ;;
Unrecognized [@@deriving] annotation syntax
#