]>
On Thu, Aug 23, 2007 at 08:32:22PM -0400, Brian Hurt wrote:
>
> I should just know this. So let's say I have two module types defined:
>
> module type Foo = sig
> type 'a t
> val foo : 'a -> 'a t
> end;;
>
> module type Bar = sig
> type 'a t
> val bar : 'a -> 'a t
> end;;
>
> Now, I want to define a module that is both a Foo and a Bar without cutting
> and pasting the module definitions around. I've been trying to do:
>
> module Baz : sig
> type 'a baz
> include Foo with type 'a t = 'a baz
> include Bar with type 'a t = 'a baz
> end;;
>
> but this blows up on the Bar line (multiple definitions of 'a t).
>
> There is a solution to this, I'm just being stupid and forgetting what it
> is. Hints would be appreciated.
>
> Brian
I might haven't got exactly what you want,
but, with control over Foo and Bar,
and starting from the structure,
I would have written :
module type Foo =
functor (T: T) ->
sig val foo : 'a -> 'a T.t end
module type Bar =
functor (T: T) ->
sig val bar : 'a -> 'a T.t end
module Baz =
functor (T: T) ->
functor (Foo: Foo) ->
functor (Bar: Bar) ->
struct
include T
type 'a baz = 'a t
module Foo = Foo(T)
module Bar = Bar(T)
include Foo
include Bar
end
Then I would have generated the signature automatically with -i.
But if you really want a short .mli without redundancy,
I see no solution, even for the above functorized code.
Because :
1/ unable to override or delete elements from a signature
2/ unable to get the signature of a structure
from a functor in a signature.
I mean, given this :
module type T = sig end
module type F =
functor (T: T) ->
sig end
This signature does not work :
module B :
functor (T: T) ->
functor (F: F) ->
sig module M : F(T) end
nor this :
module B :
functor (T: T) ->
functor (M: F(T)) ->
sig end
nor this :
module B :
functor (T: T) ->
functor (F: F) ->
sig include F(T) end
nor this :
module B :
functor (T: T) ->
functor (F: F) ->
sig open F(T) end
Despite the fact that the structured version of
the first two signatures work.
And that I do not understand why they all do not work,
since it's a kind of substitution, isn't it?
Anyway, hope you'll find a way to _avoid_ your problem.