Re: BUG #14046: Bad mathematical rules for 0 cast

On Fri, Mar 25, 2016 at 3:56 AM, <jaroslaw.stoklosa@nomino.pl> wrote:

> The following bug has been logged on the website:
>
> Bug reference:      14046
> Logged by:          Jaros=C5=82aw Stok=C5=82osa
> Email address:      jaroslaw.stoklosa@nomino.pl
> PostgreSQL version: 9.4.5
> Operating system:    x86_64-redhat-linux-gnu
> Description:
>
> Below query should return 2 times TRUE.
>
> SELECT cast('+0' as FLOAT) =3D cast('-0' as FLOAT), cast('+0' as FLOAT)::=
TEXT
> =3D cast('-0' as FLOAT)::TEXT
>
> +0 and -0 should be casted to +0 or 0.
>

=E2=80=8BI humbly disagree with you. PostgreSQL use IEEE 754 for floating p=
oint
(mainly because that is what most - not all - computers today use). IEEE
754 distinguishes +0 (or just 0) from -0. cast('-0' as FLOAT) results in an
IEEE 754 negative zero. Which is not identically equal to a positive zero.
The case to TEXT should, and does, preserve this non-identical difference. =
=E2=80=8B



>
> Regards
>
>
>
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--=20
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Maranatha! <><
John McKown