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Date: | 2009-05-26 (12:37) |
From: | Julien Signoles <Julien.Signoles@c...> |
Subject: | Re: [Caml-list] small typing problem with modules ... |
Hello, > My problem here is that I'd like to have a module type T for the functor > Make in b.ml and to avoid the signature duplication in b.mli ... ideally > I'd like to write in b.mli something like : > > module type T = sig ???? end > module Make : functor (Extra : A.Extra) -> > functor (A : A.T with type extra = Extra.t) -> T with ... > include T with ... > > It's clear that I cannot write a module type as follows because the > the "open A" will consider the default type of A and not it's > parametrized version ... > > module type T = sig > open A > val f : extra -> unit > end > > how can I parametrize this signature ? I can write something like : > module type T = functor (A : A.T) -> > sig > open A > val f : extra -> unit > end ;; > > but then I'm a bit lost putting all this together ... > I know I'm close ... a small hint ? Hum, module types cannot be parameterized. If you want to use a functor signature, you can write the following : ===== module type T = functor (Extra : A.Extra) -> functor (A : A.T with type extra = Extra.t) -> sig val f : A.extra -> unit end module Make : T open A val f : extra -> unit ===== But I'm pretty sure that is not really what is expected... However why cannot you just add an another abstract type in your signature like below? ===== module type T = sig type extra val f : extra -> unit end module Make(Extra : A.Extra)(A : A.T with type extra = Extra.t) : T with type extra = A.extra open A val f : extra -> unit ===== Hope this helps, Julien Signoles