From: Basile Starynkevitch <basile@starynkevitch.net>
To: Jean-Baptiste Jeannin <jeannin@cs.cornell.edu>
Cc: "caml-list@inria.fr" <caml-list@inria.fr>
Subject: Re: [Caml-list] Cyclic data structures: internal representation
Date: Mon, 12 Nov 2012 09:55:26 +0100 [thread overview]
Message-ID: <20121112085526.GA31519@ours.starynkevitch.net> (raw)
In-Reply-To: <A7FC6DE86AF33142A1FA4CE04EEBF4F18596A9DD62@gobo.cs.cornell.edu>
On Mon, Nov 12, 2012 at 01:44:55AM -0500, Jean-Baptiste Jeannin wrote:
> Good morning,
>
> One can create cyclic data structures in OCaml, using the keyword let rec. For example:
>
> # let rec l0 = 1 :: 2 :: l0;;
> var l0 : int list =
> [1; 2; 1; 2; 1; 2; 1; 2; 1; 2; 1; 2; 1; 2; 1; 2; 1; 2; ...]
>
> I am wondering what the internal representation (in the AST) of such a data structure is.
It is related to the notion of statically constructive expressions, see section 7.3 of the ocaml manual
http://caml.inria.fr/pub/docs/manual-ocaml-4.00/manual021.html
statically constructive expressions (which *exclude* function applications, and conditionals) can be first constructed (as yet-unfilled values) then filled. In that case, the compiler emit first the code for all the constructions, then the code for all the filling (taking into account the recursively bound variables).
This is not Ocaml specific; any Lisp or Scheme (or related, e.g. http://gcc-melt.org/ for example)
language also do that to implement let-rec kind of mutually recursive definitions.
A very good explanation about that happens in Christian Queinnec "Lisp In Small Pieces" books.
If you read french, you could read the latest variant in Franch on
http://paracamplus.com/?CGIRunMode=book&urn=Cours/LiSP/4
Principes d'implantation de Scheme et Lisp
ISBN 978-2-916466-03-3
Regards
--
Basile STARYNKEVITCH http://starynkevitch.net/Basile/
email: basile<at>starynkevitch<dot>net mobile: +33 6 8501 2359
8, rue de la Faiencerie, 92340 Bourg La Reine, France
*** opinions {are only mines, sont seulement les miennes} ***
next prev parent reply other threads:[~2012-11-12 8:55 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-11-12 6:44 Jean-Baptiste Jeannin
2012-11-12 8:55 ` Basile Starynkevitch [this message]
2012-11-12 9:43 ` Gabriel Scherer
2012-11-12 11:24 ` Dmitry Grebeniuk
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