Re: [Caml-list] How can I set a type parameter of Map.Make(X) ?

[Dumitru Potop-Butucaru <dumitru.potop_butucaru@inria.fr>]

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Yes, but this involves duplicating code, and I really hate to duplicate 
code, even in interfaces.

To also answer Ashish: I want to define an interface to modules where I 
use a very specific kind of map. Of course, I could leave Map.Make 
polymorphic, but that is a different module type than the one I want to 
use to represent my theory.

Yours,
Jacky


On 20/09/2010 19:58, Martin Jambon wrote:
> Dumitru Potop-Butucaru wrote:
>> Actually, I was looking for a way to specialize a whole module,
>> not just the associated type (**this** I knew how to do).
>> I would like to write something like:
>>
>>      include module type of Set.Make(String) with 'a= int
>>
>> Is this possible?
> I don't know about such a shortcut, but the following works and the interface
> is easier to use for a human:
>
> (* foo.mli *)
> type key = string
> type value = string
> type map
> val empty : map
> val is_empty : map ->  bool
> val add : key ->  value ->  map ->  map
> val find : key ->  map ->  value
> val remove : key ->  map ->  map
> val mem : key ->  map ->  bool
> val iter : (key ->  value ->  unit) ->  map ->  unit
> val map : (value ->  value) ->  map ->  map
> val mapi : (key ->  value ->  value) ->  map ->  map
> val fold : (key ->  value ->  'a ->  'a) ->  map ->  'a ->  'a
> val compare : (value ->  value ->  int) ->  map ->  map ->  int
> val equal : (value ->  value ->  bool) ->  map ->  map ->  bool
>
>
> (* foo.ml *)
> module M = Map.Make (String)
> include M
> type value = string
> type map = string M.t
>
>
>
> Martin
>
>
>> Yours,
>> Jacky Potop
>>
>>
>>
>>
>> On 20/09/2010 16:57, Ashish Agarwal wrote:
>>> module M = Map.Make(String)
>>>
>>> type t = int M.t
>>>
>>> Type t is the type of maps from string's to int's. Or alternatively
>>> write a
>>> function that assumes 'a is some specific type:
>>>
>>> # let f m = M.fold (fun _ x y ->   x + y) m 0;;
>>> val f : int M.t ->   int =<fun>
>>>
>>>
>>> On Mon, Sep 20, 2010 at 10:35 AM, Dumitru Potop-Butucaru<
>>> dumitru.potop_butucaru@inria.fr>   wrote:
>>>
>>>> Hello,
>>>>
>>>> I'm certain most users here will consider the question trivially simple,
>>>> but I browsed the documentation without finding a solution.
>>>>
>>>> The question is quite general: Given a polymorphic definition like
>>>> Map.Make(X), where
>>>> X is some module, how can I specialize its 'a type parameter, e.g. by
>>>> setting it to Y, so that
>>>> I have maps from X to Y ?
>>>>
>>>> Yours,
>>>> Jacky Potop
>>>>
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