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Date: Wed, 15 Oct 2003 13:33:51 +0200 (CEST)
From: Martin Jambon <martin_jambon@emailuser.net>
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To: caml-list@inria.fr
Subject: [Caml-list] Pseudo-extensible records
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X-Spam: no; 0.00; mli:01 subtyping:01 hand-written:01 labels:01 marshal:01 float:02 float:02 objects:02 objects:02 jambon:02 jambon:02 module:03 classes:03 types:03 types:03 
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Hello,

I was thinking of some way to define record types with
"the same fields plus some others":

(** point2.mli **)
type point2 = { x : float;
                y : float }

(** point3.ml **)
type point3 = { include Point2.point2;
                z : float }

(* which would be exactly equivalent as writing *)
type point3 = { x : float;
                y : float;
                z : float }

Some disavantadges:
- same field labels but no subtyping
  (and all the usual problems that we don't have with classes and objects)

Some advantages:
- can be used where objects cannot (input/output_value are possible)
- makes some type definitions more clear


My initial problem is to input/output objects with a minimum of efforts.
If we have one module for each class, with some hand-written conversion
from/to record types, maybe it would be convenient to have a
such a pseudo-inheritance system for record types.

Any experience with this kind of problem?

Unless Marshal becomes available for objects?...


-- Martin

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