From: Martin Jambon <martin.jambon@ens-lyon.org>
To: Brian Hurt <bhurt@janestcapital.com>
Cc: Sam Steingold <sds@gnu.org>, caml-list@inria.fr
Subject: Re: [Caml-list] List.cons and "::"
Date: Tue, 17 Jul 2007 22:38:37 +0200 (CEST) [thread overview]
Message-ID: <Pine.LNX.4.64.0707172231360.18640@martin.ec.wink.com> (raw)
In-Reply-To: <469D235E.9000008@janestcapital.com>
On Tue, 17 Jul 2007, Brian Hurt wrote:
> Sam Steingold wrote:
>
>> -----BEGIN PGP SIGNED MESSAGE-----
>> Hash: SHA1
>>
>> Why is :: a syntax, not an infix version of List.cons
>> (which for some reason is missing)?
>> thanks.
>>
>>
>
> So it can be used in pattern matching. Things used in pattern matching the
> compiler has to know about, and thus the user can't override. Things not
> used in pattern matching can be overridden. So you can redefine + if you
> wanted to. I wouldn't recommend it, but you could.
> : : and , you can't override.
:: and () are just constructors with a special syntax.
You can override them:
Objective Caml version 3.09.3
# type zarbi = :: of int * int | ();;
type zarbi = :: of int * int | ()
# ();;
- : zarbi = ()
# 1 :: 2;;
- : zarbi = :: (1, 2)
It's just that constructors are not automatically associated with a
function, in OCaml.
Martin
--
http://martin.jambon.free.fr
next prev parent reply other threads:[~2007-07-17 20:38 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-07-17 20:02 Sam Steingold
2007-07-17 20:15 ` [Caml-list] " Brian Hurt
2007-07-17 20:38 ` Martin Jambon [this message]
2007-07-17 22:02 ` code17
2007-07-17 20:46 ` [Caml-list] " Chris King
2007-07-18 21:36 ` Pierre Etchemaïté
2007-07-17 22:33 ` Jon Harrop
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