From: nakata keiko <keiko@kaba.or.jp>
To: damien.doligez@inria.fr
Cc: caml-list@inria.fr
Subject: Re: [Caml-list] Type constraints
Date: Wed, 08 Dec 2004 12:30:51 +0900 (JST) [thread overview]
Message-ID: <20041208.123051.74739504.keiko@kaba.or.jp> (raw)
In-Reply-To: <41B62407.4020102@inria.fr>
Damien Doligez wrote:
>The typing algorithm is very simple (really!):
>
>1. Type the module. Generalization occurs and the v field gets a
> polymorphic type.
>2. Type "M.v". This takes an instance of the polymorphic type.
>3. Can we generalize it? Look at the syntactic shape of the expression
> (in this case, let module ... in ...). If it is always safe to
> generalize such expressions, OK. If not, do not generalize.
>
>That's the beauty of the Wright criterion: it's very easy to implement
>and to understand (because it is syntactic), and works well in almost
>all
>cases (with a little eta-expansion if needed).
This does not answer to me why this works,
#type t = { t : 'a. 'a -> 'a}
#let v = let module M = struct let t x = x end in {t = M.t} in (v.t 5, v.t true)
Of cource, both of the following are not type checked,
#let v = let module M = struct let t = x end in M.t in (v 5, v true)
#let v : 'a -> 'a = let module M = struct let t x = x end in M.t in (v 5, v true)
However, if I can write something like
#let v : 'a. 'a -> 'a = let module M = struct let t x = x end in M.t in (v 5, v true)
then, it would be type checked ?
Regards,
Keiko.
next prev parent reply other threads:[~2004-12-08 3:30 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-12-06 19:55 Jim Farrand
2004-12-07 7:12 ` [Caml-list] " Alain Frisch
2004-12-07 13:43 ` Damien Doligez
2004-12-07 14:57 ` Andreas Rossberg
2004-12-07 17:44 ` Damien Doligez
2004-12-07 18:08 ` Alain Frisch
2004-12-07 21:04 ` Damien Doligez
2004-12-07 21:43 ` Alain Frisch
2004-12-08 3:30 ` nakata keiko [this message]
[not found] ` <8002B033-4906-11D9-8195-000D9345235C@inria.fr>
2004-12-09 0:56 ` nakata keiko
2004-12-09 1:27 ` Jacques Garrigue
2004-12-08 10:53 ` Damien Doligez
2004-12-08 12:39 ` Alain Frisch
2004-12-08 14:23 ` Jacques Garrigue
2004-12-09 3:07 ` skaller
2004-12-09 4:53 ` Jacques Garrigue
2004-12-08 16:10 ` Xavier Leroy
2004-12-07 18:13 ` William Lovas
2004-12-08 0:27 ` Jacques Garrigue
2004-12-07 18:41 ` Boris Yakobowski
2004-12-07 19:38 ` Jim Farrand
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