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Writing Identity Functors (or Wrapper modules) in OCAML
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Date: -- (:)
From: Merijn de Jonge <merijn.de.jonge@g...>
Subject: Re: [Caml-list] Writing Identity Functors (or Wrapper modules) inOCAML
Hi guys,

Thank you all for the quick reply.

I overlooked the paragraph "Re-exported variant type or record type: an
equation, a representation."  Adding the "type representation" did the
trick.
I needed a concrete type, so the solution to make it abstract is not
appropriate in my case.

Thanks agin.

Merijn de Jonge


On 2/27/06, Sebastian Egner <sebastian.egner@philips.com> wrote:
>
>
> > >       module type IHelloWorld =
> > >       sig
> > >          type helloWorldType = Hello | World
> > >         val hello : unit -> helloWorldType
> > >       end
> > >
> > >       module Wrapper (X: IHelloWorld) : IHelloWorld =
> > >       struct
> > >         type helloWorldType = X.helloWorldType
> > >         let hello = X.hello
> > >       end
> >
> > You have to explicitely define Hello and World in the wrapper. Try this
> :
> >
> > module Wrapper(X:IHelloWorld): IHelloWorld =
> > struct
> >   type helloWorldType = X.helloWorldType = Hello | Word
> >   let hello = X.hello
> > end
>
> Alternatively, you have defined too much In IHelloWorld
> (depends on what you wanted to do in the first place).
> Then try this:
>
>       module type IHelloWorld =
>       sig
>         type helloWorldType (* now abstract *)
>         val hello : unit -> helloWorldType
>       end
>
>       module Wrapper (X: IHelloWorld) :
>         (IHelloWorld with type helloWorldType = X.helloWorldType) =
>       struct
>         type helloWorldType = X.helloWorldType
>         let hello = X.hello
>       end
>
>         ...
>
> Sebastian Egner.