Re: Very general OCaml questions

[Thomas Gazagnaire <thomas.gazagnaire@xxxxxxxxx>]

> 1) ----------------------
> I want to define a signpost tactic as a package of functionality with a well 
> defined and known signature.
> Modules would be perfect, if it wasn't for the fact that I want to be able to 
> pass around all the signpost tactics as a list, and since modules aren't 
> first class data, like functions, I cannot do something like
> 
> let tactics = [iodine; OpenVPN; Tor; etc]
> 
> and then later call the functions defined in the modules...
> 
> I could define the tactics as classes since I could then easily pass them 
> around, but I feel somewhat dirty using classes in a nice functional language.
> 
> An option could be to combine modules and records, where the standard set of 
> functions are exposed in the record, and from there invoke the module 
> functions, but that doesn't seem very natural or clean either.
> 
> What is the preferred approach?

You can also use first-class modules:

module type S = sig
  val f : int -> int
end

module A = struct
  let f x = x
end

module B = struct
  let f x = x * x
end

let modules = [| (module A : S); (module B : S) |]
  
let f i =
  let module M = (val modules.(i) : S) in
  M.f

If you are defining an abstract type in S, it becomes a bit more complex, but 
otherwise it's fine.

--
Thomas