Re: things about grouping

On Wed, Nov 28, 2012 at 10:14 AM, David Carlisle <davidc@xxxxxxxxx> wrote:
> On 28/11/2012 10:04, Ihe Onwuka wrote:
>>
>> If you are going to support an operator called except then its
>> semantics should be that such that it takes its context from its
>>
>> left hand side consistent with the semantic we have grown up with
>> since childhood
>
>
> I wasn't involved in the naming but I'd think far more people would guess
> what it does given A except B than A difference B. I think your assertion
> that except implies context dependence dependence isn't that clear even in
> English language, and the connection between English language usage and the
> detailed Xpath semantics are tenuous at best.
> You would not be able to guess the exact (or even any ) behaviour of XPath
> "for" from its use in English.
>

The semantic of difference in a set theoretic construct is
unambiguous. By your argument above same cannot be said for except.
My salient  point then is that is an additional reason why difference
should be part of the syntax and except should not.

PS If we were to go down the route of choosing syntax that people
would guess from then intersect then there is an argument for calling
intersect Both. Don't want to go there.