Hi Paolo,

Paolo Donadeo wrote:
> I'm using Sexplib to store and retrieve the sessions of a web
> application into a data base. A "session" has this signature:
> 
> module type SESSION_DATA =
>   sig
>     type t
>     val default : t
>     val string_of_t : t -> string (* Is this what you want? *)
>     val t_of_string : string -> t (* Is this what you want? *)
>   end
> 
> and the concrete session, which is a blog session, is:
> 
> module Blog_session =
>   struct
>     type user =
>       {
>         email : string;
>         passwd : string;
>         first_name : string option;
>         last_name : string option;
>         displ_name : string option;
>         website : string option
>       } with sexp
> 
>     type t =
>       | Anonymous
>       | Logged of user
>         with sexp
> 
>     let default = Anonymous
> 
>     let string_of_t = sexp_of_t |- Sexplib.Sexp.to_string_hum |- hex_encode
> 
>     let t_of_string s =
>       try s |> hex_decode |> Sexplib.Sexp.of_string |> t_of_sexp
>       with Sexplib.Conv.Of_sexp_error (_, _) -> default
>   end
> 

My be a solution. Going to see if I can find an alternate
implementation of hex encoding so as not to require another
library.

Thanks,
Hugo F.


> Functions "hex_encode" and "hex_decode" are trivially implemented
> using Cryptokit:
> 
> let hex_encode = Cryptokit.transform_string (Cryptokit.Hexa.encode ())
> let hex_decode = Cryptokit.transform_string (Cryptokit.Hexa.decode ())
> 
> The operators (|-) and (|>) are defined as always:
> 
> http://thelema.github.com/batteries-included/hdoc/BatPervasives.html#6_Fundamentalfunctionsandoperators
> 
> 
> Hope this helps,
> 
>