CODEWITHSUNDEEP
ocaml
njb
njb

Reputation: 93

referencing a module type signature

I'm trying to reference a type in a module signature to build another type.

module type Cipher = sig

  type local_t
  type remote_t

  val local_create : unit -> local_t
  val local_sign : local_t -> Cstruct.t -> Cstruct.t
  val remote_create : Cstruct.t -> remote_t
  val remote_validate : remote_t -> Cstruct.t -> bool

end

module Make_cipher :                                                              
  functor (Cipher_impl : Cipher) ->
    sig                                                                         
      type local_t = Cipher_impl.local_t                                        
      type remote_t = Cipher_impl.remote_t
      val local_create : unit -> local_t
      val local_sign : local_t -> Cstruct.t -> Cstruct.t
      val remote_create : Cstruct.t -> remote_t
      val remote_validate : remote_t -> Cstruct.t -> bool
    end

type self_t = 
  {
    mutable modules : (module Cipher) list;
    mutable locals : Cipher.local_t list;
  }

When I compile this, I get 'Error: Unbound module Cipher' for self_t. I'm not too sure what to do here.

Upvotes: 4

Views: 395

Answers (1)

ivg
ivg

Reputation: 35280

In short, you should use Cipher_impl.local_t instead of Cipher.local_t

A module type (aka signature) is just a specification of module interface. When you need a type, you need to refer to a particular type in a particular module, not in the signature.

Upvotes: 4

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