Bug #644: Incorrect result in math operation

Francisco Blay (franblay(at)ono(dot)com) reports a bug with a severity of 3
The lower the number the more severe it is.

Short Description
Incorrect result in math operation

Long Description
3088.8 - (2847.64 + 241.16)=4.54747350886464e-13
It's spected to be 0.0 the result of this operation (I think)
Got the same results in

PIII:

franblay=> select version();
version
---------------------------------------------------------------
PostgreSQL 7.0.3 on i686-pc-linux-gnu, compiled by gcc 2.95.2
(1 row)

AMD Athlon:

datadb=# select version();
version
-------------------------------------------------------------
PostgreSQL 7.2 on i686-pc-linux-gnu, compiled by GCC 2.95.2
(1 row)

Both SuSE 7.0
Libraries:
libe2p.so.2 libpam.so.0
libe2p.so.2.3 libpam.so.0.72
libext2fs.so.2 libpam_misc.so.0
libext2fs.so.2.4 libpam_misc.so.0.72
ld-2.1.3.so libhistory.so.4 libpamc.so.0
ld-linux.so.1 libhistory.so.4.1 libpamc.so.0.72
ld-linux.so.1.9.9 libm.so.6 libpthread.so.0
ld-linux.so.2 libncurses.so.4 libreadline.so.4
ld.so libncurses.so.4.2 libreadline.so.4.1
ld.so.1.9.9 libncurses.so.5 libresolv.so.2
libBrokenLocale.so.1 libncurses.so.5.0 librt.so.1
libNoVersion.so.1 libnsl.so.1 libss.so.2
libSegFault.so libnss_compat.so.2 libss.so.2.0
libc.so.6 libnss_db.so.2 libthread_db.so.1
libcom_err.so.2 libnss_dns.so.2 libutil.so.1
libcom_err.so.2.0 libnss_dns6.so.2 libuuid.so.1
libcrypt.so.1 libnss_files.so.2 libuuid.so.1.2
libdb.so.2 libnss_hesiod.so.2
libdb.so.3 libnss_nis.so.2
libdl.so.2 libnss_nisplus.so.2

Sample Code
datadb=# select 3088.8 - 3088.8 AS ok;
ok
----
0
(1 row)

datadb=# select 3088.8 - (2847.64 + 241.16) AS silly;
silly
----------------------
4.54747350886464e-13
(1 row)

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