message.ml

open Core.Std
module T = Core.Time


module Message = struct

  exception Invalid_message_format of string
  
  type msg = {
    channel : string
  ; nick    : string
  ; message : string
  ; date    : float
  }

  type info = {
    channel : string
  ; message : string
  ; date    : float
  }
                
  type t =
    | Msg of msg
    | Info of info

  let is_info_marker = function
    | "<--" -> true
    | "-->" -> true
    | _     -> false

  let of_date_string s =
    (T.of_string s) |> T.to_float

  let of_string ~raw ~channel =
    let msg = String.split raw '\t' in
    match msg with
    | [] -> assert false
    | [date; nick; message] when is_info_marker nick ->
       let date = of_date_string date in
       Info {channel;message;date}
    | [date; nick; message] ->
       let date = of_date_string date in
       Msg {channel;nick;message;date}
    | _ -> raise (Invalid_message_format raw)
end

1. I'd indent the records and drop-down the 1st brace:

type info =
  { channel : string
  ; message : string
  ; date    : float
  }

2. Instead of exception, I'd use Result.t

3. Take a look at Str and Re modules, though I'd prefer to use ocamllex

Thanks!