Re: BUG #8317: ROUND(double*1/2) != ROUND(1/2*double)

On 2013-07-22 09:44:58 +0000, remi(dot)cura(at)gmail(dot)com wrote:
> The following bug has been logged on the website:
>
> Bug reference: 8317
> Logged by: Rémi
> Email address: remi(dot)cura(at)gmail(dot)com
> PostgreSQL version: 9.2.4
> Operating system: Ubuntu 12.0.4 32 bits hosted by a VirtualBox
> Description:
>
> Hello;
> I ran into a strange behaviour.
> Initially it showed in a group by, but is also happens in regular select :
>
>
> example :
> SELECT 2*ROUND(1/2*3.2)
> --> gives 0
> SELECT 2*ROUND(3.2*1/2)
> --> gives 3
>
>
> Obviously both should return the same thing, preferably 3.
> It looks like a bug to me, or at least a non desirable behaviour.

Hm. Doesn't really look like a bug to me. The first parses as:
ROUND((1/2) * 3.2), the second as ROUND((3.2 * 1) / 2). So the different
result makes sense to me.

Greetings,

Andres Freund

--
Andres Freund http://www.2ndQuadrant.com/
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