From: David Teller <David.Teller@univ-orleans.fr>
To: OCaml <caml-list@inria.fr>
Subject: Polymorphic variant as a witness?
Date: Sun, 22 Jun 2008 01:11:59 +0200 [thread overview]
Message-ID: <1214089919.6190.13.camel@Blefuscu> (raw)
Dear list,
I have been thinking for some time about using polymorphic variants to
encode some aspects of a types-and-effects type system in OCaml using
Camlp4. While the idea is still quite fuzzy, I have the feeling that, if
I could have a value (let's call it "witness") with type
[> ] ref
which I could "touch" into becoming
[> `A] ref
then
[> `A | `B] ref
etc. as effects `A, `B, etc. appear in the program, it could provide
interesting information on the effects of the program.
Now, of course, I can't define a value with type ref [> ] or even with
type ref [> `dummy]. That is, when compiling a module consisting only in
a declaration such as
let witness = ref `dummy
I'm faced with the good old "cannot be generalised" error message. This
strikes me as normal -- I'm sure that, with the right modifications on
witness, I could cause runtime type inconsistencies for any client
attempting to read the value of witness. However, in this case, I'm not
going to read any value from witness, ever. I only want to "touch" it
into becoming something a tad more complex, which I could then look at
with ocamlc -i or such.
My question is: is there a way to hijack polymorphic variants into doing
what I wish? Or to encode this behaviour somehow?
Thanks,
David
--
David Teller
Security of Distributed Systems
http://www.univ-orleans.fr/lifo/Members/David.Teller
Angry researcher: French Universities need reforms, but the LRU act brings liquidations.
next reply other threads:[~2008-06-21 23:08 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-06-21 23:11 David Teller [this message]
2008-06-21 23:27 ` [Caml-list] " Christophe TROESTLER
2008-06-21 23:52 ` David Teller
2008-06-23 8:13 ` Romain Bardou
2008-06-23 10:27 ` Jacques Garrigue
2008-06-27 6:00 ` David Teller
2008-06-27 6:38 ` Jacques Garrigue
2008-07-04 13:05 ` Polymorphic variant + phantom type as a witness Gleb Alexeyev
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