[sc34wg3] TMQL: Operators "Not equal"
rho at devc.at
Mon Oct 29 05:33:45 EDT 2007
On Fri, Oct 26, 2007 at 05:22:25PM +0200, Lars Heuer wrote:
> The current draft lacks of a not equal operator, like "!=". Is that
> A not equal operator is quite handy even if
> not(1.0 = 2.0)
> works, though.
'==' has 'exists semantics' as it is operating on sequences! So
select $p / name
$p isa person
& $p / homepage != "http://myspace.com/"
might not really signal what is going on. If I read the above quickly,
then I would select all persons which have not a homepage at MySpace.
But what it means is
not ($p / homepage == "http://myspace.com/")
So I'm actually asking for all persons where it is
"not true, that there is at least one MySpace homepage"
The proposed notation
$p / homepage != "http://myspace.com/"
would more indicate
"no homepage is on MySpace"
This is also the reason to prefer '==' over '=', because the query
author should keep that in mind.
And then he said: "You should read my blog." http://kill.devc.at/
More information about the sc34wg3