From: micha <micha-1@fantasymail.de>
To: ocaml <caml-list@inria.fr>
Subject: phantom type thing question
Date: Thu, 01 Mar 2007 10:46:14 +0100 [thread overview]
Message-ID: <45E6A0E6.80502@fantasymail.de> (raw)
I'm getting confused while trying to implement some subtyping hierachy
with polymorphic variants.
say I have the hierachy:
symbol -> image -> xpmimage
and types like that:
type 'a sym;;
make_symbol : params -> [`Symbol] sym;;
make_image: params -> [`Image] sym;;
or should it be:
make_image: params -> [`Symbol | `Image] sym;;
make_xpm; params -> [`Symbol | `Image | `Xpm ] sym;;
so that some functions work only on some symbols:
val get_image_width: [< `Image | `XpmImage] sym -> int;;
I think I mix up the [< ..] and [> ... ] type constructs, allthough I
thought I understood it :-)
Michael
next reply other threads:[~2007-03-01 9:45 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-03-01 9:46 micha [this message]
[not found] ` <95513600703010547t1f098d80p7bbff2f2c85d79a5@mail.gmail.com>
2007-03-01 13:49 ` [Caml-list] " Olivier Andrieu
2007-03-01 16:40 ` micha
2007-03-01 17:03 ` Olivier Andrieu
2007-03-01 20:01 ` micha
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