From: Philippe Wang <lists@philippewang.info>
To: Lukasz Stafiniak <lukstafi@gmail.com>, ocaml ml <caml-list@inria.fr>
Subject: Re: [Caml-list] How do I get polymorphic partial application?
Date: Sun, 24 Jun 2007 00:11:18 +0200 [thread overview]
Message-ID: <467D9A86.301@philippewang.info> (raw)
In-Reply-To: <4a708d20706231449g38836405xc48f4eb6fa82d779@mail.gmail.com>
Lukasz Stafiniak wrote:
> On 6/23/07, Philippe Wang <lists@philippewang.info> wrote:
>> Till Varoquaux wrote:
>> > Humm... I have a small issue here: I need to get the result of the
>> > partial application of a polymorphic function. Since variable are
>> > generalized in Let it is generally advised to use eta expansions,
>> > (i.e transform to a total application).
>> > sometimes eta expansions just won't do the trick, consider:
>>
>> I think you should not try to "hide" that ugly side effect...
>>
> Could someone give an example where this "eta-thing" forbids a crash?
> I don't remember any example even in Xavier Leroy papers.
If I understand what you mean, this could explain it :
let foo () =
let container = ref [] in
fun x -> container := x :: !container; !container
val foo : unit -> 'a -> 'a list
(* first : doesn't work *)
let plop = foo ()
let l1 = plop 42
let l2 = plop "42" (* crash -- but wouldn't crash with most *dynamic*
typing systems *)
let plop2 = fun () -> foo ()
let l1' = plop2 () 42
let l2' = plop2 () "42" (* no crash *)
but plop and plop2 don't share the same semantics...
--
Philippe Wang
mail[at]philippewang.info
next prev parent reply other threads:[~2007-06-23 22:11 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-06-23 18:55 Till Varoquaux
2007-06-23 21:41 ` [Caml-list] " Philippe Wang
2007-06-23 21:49 ` Lukasz Stafiniak
2007-06-23 22:09 ` Till Varoquaux
2007-06-23 22:25 ` Lukasz Stafiniak
2007-06-23 22:11 ` Philippe Wang [this message]
2007-06-23 22:28 ` Lukasz Stafiniak
2007-06-23 22:07 ` Zheng Li
2007-06-23 22:09 ` Zheng Li
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