OCaml version 4.02.0

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    [| +   | |   Batteries 2.3  - |
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     | -  Type '#help;;'    | | + |]
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# module StrKey =
  struct
    type t = string
    let equal s1 s2 = ( s1 == s2 )
    let hash s = ( Hashtbl.hash  s )
  end;;
          module StrKey :
  sig type t = string val equal : 'a -> 'a -> bool val hash : 'a -> int end
# module type of Hashtbl.Make( StrKey );;
Characters 12-14:
  module type of Hashtbl.Make( StrKey );;
              ^^
Error: Syntax error
# module type Hashtbl.Make( StrKey );;
Characters 19-20:
  module type Hashtbl.Make( StrKey );;
                     ^
Error: Syntax error
#