[Ocaml-lib-devel] Re: Re: Env module?

[Jesse G. <je...@wi...>]

Jesse Guardiani wrote:

> On Sunday 15 August 2004 06:31, Nicolas Cannasse wrote:
> 
> [...]
> 
>> > I like the data hiding that objects provide. The above module you have
>> > defined is only good for a local fabricated environment.
>>
>> That's were the devil is hidding.
>> You should actually treat uniformaly any environement, local or "built".
>> I makes things a lot easier, especially when for example you start
>> writting code modifying your local env and you want to switch later to
>> "built" env for different kind of reasons. You shouldn't rewrite anything
>> this time. Here's an improved interface :
>>
>> type t = (string , string ) Hashtbl.t
>>
>> val get : t -> string -> string option
>> val default : t -> def:string -> env:string -> string
>> val put : t -> string -> string -> unit
>> val exists : t -> string -> bool
>>
>> val process : unit -> t (* return the current process env *)
>> val dup : t -> t (* duplicate an environement (can be useful) *)
>> val to_array : t -> string array
>> var set : t -> unit (* set the current process env *)
> 
> I like this interface, but the more I play with it the more I realize that
> we're still wrapping Hashtbl. The entire interface can be reduced to this:
> 
> val process : ?size:int -> unit -> (string, string) Hashtbl.t
> val to_array : (string, string) Hashtbl.t -> string array
> val set : (string, string) Hashtbl.t -> string -> unit
> 
> There's no need for an additional type.

I've implemented this, as well as the get, strict_get, default, and put
functions. I justified implementing these by restricting their type arguments,
and causing the get like functions to raise Invalid_argument instead of
Not_found for a bit more detailed exceptions:

sig
  val from_array : ?size:int -> string array -> (string, string) Hashtbl.t
  val process : ?size:int -> unit -> (string, string) Hashtbl.t
  val to_array : (string, string) Hashtbl.t -> string array
  val set : (string, string) Hashtbl.t -> string -> unit
  val get : (string, string) Hashtbl.t -> string -> string
  val strict_get : (string, string) Hashtbl.t -> string -> string
  val default : ?def:string -> (string, string) Hashtbl.t -> string -> string
  val put : (string, string) Hashtbl.t -> string -> string -> unit
end

It compiles, but I haven't tested it yet. :) Consider it just a proof of
concept for now until I can thoroughly test it later today.

You can check it out here:
    http://www.wingnet.net/~jesse/ocaml/env/doc/Env.html

Click the (.ml) at the top to view the full source.

What does everyone think?

-- 
Jesse Guardiani, Systems Administrator
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