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From: "Mattias Engdegård" <mattias@virtutech.se>
To: jonathan.roewen@gmail.com
Cc: pal_engstad@naughtydog.com, caml-list@inria.fr
Subject: Re: [Caml-list] if (n:int) < 0 then (-n) > 0 is FALSE
Date: Thu, 7 Dec 2006 20:43:12 +0100	[thread overview]
Message-ID: <200612071943.kB7JhC522308@virtutech.se> (raw)
In-Reply-To: <ad8cfe7e0612071119k6a9c51a4s79fae5838f5d6fa1@mail.gmail.com> (jonathan.roewen@gmail.com)

>It's not a bug -- you're relying on 32bit ints when OCaml has only
>31bit ints (on 32-bit arch). In C (for example), if you use a plain
>int (I believe it'll default to signed), you get the exact same
>behaviour when the number overflows 2^31.

(Signed overflow is not legal in C (undefined behaviour), and a decent
compiler will warn this can be detected statically.)

Of course it is a bug - a design bug, since the behaviour is intended
and documented, but still a bug. But getting numbers, even integers,
right in every respect is hard, and involves trade-offs between
performance, correctness and convenience.

I would love to have a fast unboxed integer type that automatically
overflows to bignum, but it would be a tad slower than the current "int".


  reply	other threads:[~2006-12-07 19:43 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2006-12-07 18:32 Pal-Kristian Engstad
2006-12-07 19:19 ` [Caml-list] " Jonathan Roewen
2006-12-07 19:43   ` Mattias Engdegård [this message]
2006-12-07 20:02     ` Brian Hurt
2006-12-08  2:37     ` skaller
2006-12-08 11:09       ` Mattias Engdegård
2006-12-08 17:48     ` Jon Harrop
2006-12-08 18:20       ` Mattias Engdegård
2006-12-08 18:37         ` Brian Hurt
2006-12-09  2:03           ` skaller
2006-12-07 21:13 ` Martin Jambon

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