DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma;
	h=from:reply-to:to:subject:date:user-agent:cc:references:in-reply-to
	:mime-version:content-type:content-transfer-encoding
	:content-disposition:message-id;
	b=s9yQHtXgihG/jt47sPMVzdURtFKER70ft5TkZ//S2oRPlSlfgS3qPFmhtdtE3QTjDA
	/Hwl97G9BmApuagf8mYlqrTdeoIlgBAvHQuuL5rHGXUK7+kIYmBnpVznPNIH5wah5p9p
	acJJrXUQeoAjIrrXfVtET7KNBSGWq+zVuzXk8=
From: Adrian Klaver <adrian.klaver@gmail.com>
Reply-To: adrian.klaver@gmail.com
To: pgsql-sql@postgresql.org
Subject: Re: Round integer division
Date: Fri, 25 Jun 2010 16:25:48 -0700
User-Agent: KMail/1.9.10
Cc: Lee Hachadoorian <lee.hachadoorian@gmail.com>
References: <4C25334D.4040805@gmail.com>
In-Reply-To: <4C25334D.4040805@gmail.com>
MIME-Version: 1.0
Content-Type: text/plain;
  charset="iso-8859-1"
Content-Transfer-Encoding: 7bit
Content-Disposition: inline
Message-Id: <201006251625.48231.adrian.klaver@gmail.com>

On Friday 25 June 2010 3:53:01 pm Lee Hachadoorian wrote:
> Is it documented anywhere that floating-point numbers round
> "scientifically", that is 0.5 rounds to the nearest even number? Compare:
>
> SELECT round(2.5::real), round(2.5::numeric), round(3.5::real),
> round(3.5::numeric);
>
> generates
>
> 2 | 3 | 4 | 4
>
> I stumbled across this when I was trying to use round(a::real/b::real)
> to generate a rounded result to dividing integers, and noticed sometimes
> 0.5 was truncated and sometimes it was rounded up. Couldn't find
> anything about this in the archives or the data type documentation. Is
> there something obvious that I'm I missing?
>
> Thanks,
>
> --
>
> Lee Hachadoorian
> PhD Student, Geography
> Program in Earth & Environmental Sciences
> CUNY Graduate Center

See here for explanation:
http://archives.postgresql.org/pgsql-general/2010-03/msg00969.php

-- 
Adrian Klaver
adrian.klaver@gmail.com