[Caml-list] Re: modules and objects

[Vincent Poirriez <Vincent.Poirriez@univ-valenciennes.fr>]

OK , I was tired,forgive the question. the answer is obvious if for
example I remember that types
are not first class values and that a module may (and often) contains
types.

Vincent

Le Thu, 28 Nov 2002 19:14:40 +0100
Vincent Poirriez <Vincent.Poirriez@univ-valenciennes.fr > vous avez
écrit:

|Hello list,
|
|My non-important question is "why a module is not a first class
|value? while objects are."
| I was playing with modules and objects, and I found funny that it's
|possible to simulate the constructor new, just by using a functor
|taking an empty module. 
|
|module Void = struct end
|module type Unit = sig end
|
|module Build(M:Unit) = struct
| let r = ref 0
| let get () = !r
| let put i = r :=i
|end
|
|module type CONS = sig val get: unit -> int end
|module type PROD = sig val put: int -> unit end
|
|module Foo = Build(Void)
|module Bar = Build(Void)
|module FooC= (Foo:CONS)
|module FooP= (Foo:PROD)
|
|What remains impossible is:
| let lm = [FooP;FooC]  impossible
|
|While with objects:
|class build = object
|val mutable r = 0
|method get = r
|method put i = r <- i
|end
|
|let foo = new build
|let bar = new build
|
|class virtual cons = object
| method  virtual get : int
|end
|class virtual prod = object
| method  virtual put : int -> unit
|end
|let fooc = (foo :> cons)
|let foop = (foo :> prod)
|
| let lo = [foo;bar]
|
|Is correct.
|
|Vincent
|
|
|
|-- 
|courriel: vincent.poirriez@univ-valenciennes.fr  
|tel: (33)[0]3 27 51 19 53 
|Université de Valenciennes et du Hainaut-Cambrésis - Le Mont Houy
|F-59313 Valenciennes cedex 9 - FRANCE
|http://www.univ-valenciennes.fr/LAMIH/ROI/poirriez


-- 
courriel: vincent.poirriez@univ-valenciennes.fr  
tel: (33)[0]3 27 51 19 53 
Université de Valenciennes et du Hainaut-Cambrésis - Le Mont Houy
F-59313 Valenciennes cedex 9 - FRANCE
http://www.univ-valenciennes.fr/LAMIH/ROI/poirriez
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