Re: [Caml-list] What is an applicative functor?

[Julien Signoles <julien.signoles@gmail.com>]

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2011/4/11 Julien Signoles <julien.signoles@gmail.com>

> Hello Allain,
>
> 2011/4/8 Alain Frisch <alain.frisch@lexifi.com>
>
>> On 04/08/2011 01:25 PM, Julien Signoles wrote:
>>
>>> 2) module F(X:...) = G(H(X))
>>>
>>> Without applicative functors, we again get the error about parameter
>>> elimination. But I see no workaround to eliminate it without changing
>>> the signature of F. So IMHO that is a use case where applicative
>>> functors are useful.
>>>
>>
>> I'd be interested to see a full example for this case.
>>
>
> Download sources of Frama-C here :
> http://frama-c.com/download/frama-c-Carbon-20110201.tar.gz
> The use case is in module State_builder :
>
> src/project/state_builder.ml:
> (* ... *)
> module Caml_weak_hashtbl(Data: Datatype.S) =
> Weak_hashtbl(Weak.Make(Data))(Data)
> (* ... *)
>
> Do you see any workaround to compile this code with -no-app-funct (and as
> most as possible without changing API)?
>

Looking this case in details, there is actually one workaround.

src/project/state_builder.ml:
(* ... *)
module Caml_weak_hashtbl(Data: Datatype.S)(Info: Info_with_size) = struct
  module W = Weak.Make(Data)
  include Weak_hashtbl(W)(Data)(Info)
end
(* ... *)

There is still the issue with diamond import in libraries like mentionned by
Andreas.

Sorry for the noise,
Julien

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