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

On Fri, Mar 25, 2016 at 3:56 AM, <jaroslaw(dot)stoklosa(at)nomino(dot)pl> wrote:

> The following bug has been logged on the website:
>
> Bug reference: 14046
> Logged by: Jarosław Stokłosa
> Email address: jaroslaw(dot)stoklosa(at)nomino(dot)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) = cast('-0' as FLOAT), cast('+0' as FLOAT)::TEXT
> = cast('-0' as FLOAT)::TEXT
>
> +0 and -0 should be casted to +0 or 0.
>

​I humbly disagree with you. PostgreSQL use IEEE 754 for floating point
(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. ​

>
> Regards
>
>
>
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