From: Damien Doligez <damien.doligez@inria.fr>
To: "Yaron Minsky" <yminsky@cs.cornell.edu>
Cc: caml-list@inria.fr
Subject: Re: [Caml-list] Weird behavior with nan's and min/max
Date: Fri, 17 Oct 2003 00:52:02 +0200 [thread overview]
Message-ID: <5B3DCF94-002B-11D8-BC86-00039310CAE8@inria.fr> (raw)
In-Reply-To: <15352.141.155.88.179.1066340443.squirrel@minsky-primus.homeip.net>
On Thursday, October 16, 2003, at 11:40 PM, Yaron Minsky wrote:
> let is_obj_nan x =
> Obj.tag (Obj.repr x) = Obj.double_tag &&
> (let f = (Obj.magic x : float) in not (f = f))
[...]
> The resulting code segfaulted on me, and the segfault went away when I
> went back to the ordinary min and max. Does anyone have a thought on
> this? Is this use of Obj safe or not?
The problem is that the argument of Obj.tag must be a pointer value
that lives in the heap. A pointer value answers false to Obj.is_int,
but you have no way to test for heap-allocated values.
This is going to change soon because I am fixing the bug found by
Jacques with float lazy arrays, and in the process I will extend
Obj.tag to give meaningful answers for ints and non-heap-allocated
values.
In the meantime, you can use the following code, but it might still
fail in some rare cases when applied to non-heap-allocated values
(I/O channels for example):
let is_obj_nan x =
not (Obj.is_int (Obj.repr x)) &&
Obj.tag (Obj.repr x) = Obj.double_tag &&
(let f = (Obj.magic x : float) in not (f = f))
;;
-- Damien
-------------------
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
next prev parent reply other threads:[~2003-10-16 22:52 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-10-14 14:37 Yaron Minsky
2003-10-14 14:56 ` Yaron Minsky
2003-10-14 20:52 ` Yaron Minsky
2003-10-14 23:43 ` skaller
2003-10-16 17:29 ` Hendrik Tews
2003-10-16 13:16 ` Xavier Leroy
2003-10-16 14:01 ` Yaron Minsky
2003-10-17 9:26 ` [Caml-list] Test nan (was: Weird behavior with nan's and min/max) Christophe TROESTLER
2003-10-16 21:40 ` [Caml-list] Weird behavior with nan's and min/max Yaron Minsky
2003-10-16 21:50 ` Yaron Minsky
2003-10-16 22:52 ` Damien Doligez [this message]
2003-10-17 14:55 ` skaller
2003-10-17 15:14 ` Floating point exceptions (Was Re: [Caml-list] Weird behavior with nan's and min/max) Yaron Minsky
2003-10-17 23:55 ` [Caml-list] Weird behavior with nan's and min/max Yaron M. Minsky
2003-10-20 13:29 ` Xavier Leroy
2003-10-20 13:43 ` Yaron Minsky
2003-10-20 14:24 ` Xavier Leroy
2003-10-16 23:55 ` [Caml-list] " Jed Davis
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=5B3DCF94-002B-11D8-BC86-00039310CAE8@inria.fr \
--to=damien.doligez@inria.fr \
--cc=caml-list@inria.fr \
--cc=yminsky@cs.cornell.edu \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).