From: Xavier Leroy <Xavier.Leroy@inria.fr>
To: Alex Baretta <alex@barettadeit.com>
Cc: Ocaml <caml-list@inria.fr>
Subject: Re: [Caml-list] Pervasives.compare output type
Date: Wed, 30 Mar 2005 16:17:12 +0200 [thread overview]
Message-ID: <20050330141708.GB18175@yquem.inria.fr> (raw)
In-Reply-To: <42430B3B.60408@barettadeit.com>
> Pervasives.compare currently returns an int. Intuitively it would be
> more appropriate for it to return a union type such as the following.
> type comparison_result = Less | Equals | Greater
> What are the reasons behind the present design choice?
It's a historical error. If I were to do it again, I'd use a sum type
such as your "comparison_result". The current solution allows to use
(-) (integer subtraction) as the comparison predicate for *small*
integer arguments, but this doesn't work as a general integer
comparison because of subtraction wrapping around for large arguments.
So, there are really no benefits to encode the result of a 3-way
comparison as an "int".
- Xavier Leroy
next prev parent reply other threads:[~2005-03-30 14:17 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-03-24 18:47 Alex Baretta
2005-03-24 19:41 ` [Caml-list] " Richard Jones
2005-03-24 21:00 ` Marcin 'Qrczak' Kowalczyk
2005-03-24 21:38 ` Bardur Arantsson
2005-03-24 22:07 ` [Caml-list] " Jason Hickey
2005-03-24 22:26 ` brogoff
2005-03-25 9:42 ` Alex Baretta
2005-04-01 5:59 ` Aleksey Nogin
2005-03-24 22:15 ` Marcin 'Qrczak' Kowalczyk
2005-03-24 22:41 ` Bardur Arantsson
2005-03-25 9:43 ` [Caml-list] " Alex Baretta
2005-03-29 7:14 ` [Caml-list] " Oliver Bandel
2005-03-30 14:17 ` Xavier Leroy [this message]
2005-03-30 14:45 ` Alex Baretta
2005-03-30 15:11 ` Jacques Carette
2005-03-30 15:28 ` Alex Baretta
2005-03-30 17:47 ` brogoff
2005-03-30 18:21 ` Jacques Carette
2005-03-30 18:49 ` brogoff
2005-03-30 20:06 ` Jon Harrop
2005-03-30 20:43 ` Jacques Carette
2005-03-30 22:14 ` Christopher Dutchyn
2005-03-31 0:44 ` brogoff
2005-03-30 22:43 ` GADT?? (Re: [Caml-list] Pervasives.compare output type) Oliver Bandel
2005-03-30 22:35 ` [Caml-list] Pervasives.compare output type Oliver Bandel
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