BUG #2211: select (1::float-1::float)*(-1) = -0 ??

The following bug has been logged online:

Bug reference:      2211
Logged by:          Tiago D. J.
Email address:      tiago@mdtestudio.com.br
PostgreSQL version: 8.1
Operating system:   Slackware 10.2
Description:        select (1::float-1::float)*(-1) = -0 ??
Details:

Hi people,
I think that anything * 0, or 0*anything should be zero.
But run this query :
select (1::float-1::float)*(-1)

it returns -0

Sorry, my english is so poor,
I hope that i'm helping you with this information.

Tiago