English version
Accueil     À propos     Téléchargement     Ressources     Contactez-nous    

Ce site est rarement mis à jour. Pour les informations les plus récentes, rendez-vous sur le nouveau site OCaml à l'adresse ocaml.org.

Browse thread
[Caml-list] :: operator not quotable using ( ... )
[ Home ] [ Index: by date | by threads ]
[ Search: ]

[ Message by date: previous | next ] [ Message in thread: previous | next ] [ Thread: previous | next ]
Date: 2002-04-24 (10:56)
From: Remi VANICAT <vanicat@l...>
Subject: Re: [Caml-list] :: operator not quotable using ( ... )
John Prevost <visigoth@cs.cmu.edu> writes:

> When writing an example just now for this list, I noticed that you can
> no longer (assuming you ever could) write (::) or any variation
> thereof to refer to the definition of the :: cons operator.  Since
> there is no other standard way to write this, one must use:

cons is not really an operator, it's a constructor

> let cons x y = x :: y

the same hold for any constructor :

moi@debian:~/prog/ocaml-cvs$ ocaml
        Objective Caml version 3.04

# type foo =
    Bar of int * int;;
type foo = Bar of int * int
# Bar;;
The constructor Bar expects 2 argument(s),
but is here applied to 0 argument(s)

you have to write

let bar x y = Bar (x, y)

> to get one.  This is unfortunate when you wish to, say, define map in
> terms of fold.  My suspicion is that it may have worked in the past,
> but broken by keyword argument parsing.  Is there any chance (::)
> could be special cased to work correctly, even though it conflicts
> with (x : y) for typing?  I don't think it likely that anybody would
> write (::) intending to express a type.

I don't know, but the true problem is the possibility to implicitly
define function that correspond to constructor.

Rémi Vanicat
To unsubscribe, mail caml-list-request@inria.fr Archives: http://caml.inria.fr
Bug reports: http://caml.inria.fr/bin/caml-bugs FAQ: http://caml.inria.fr/FAQ/
Beginner's list: http://groups.yahoo.com/group/ocaml_beginners