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Re: [css-selectors] Proposal: Logical Combinators / Sets

From: Lea Verou <lea@w3.org>
Date: Fri, 15 Mar 2013 01:19:04 +0200
Cc: "www-style@w3.org" <www-style@w3.org>
Message-Id: <DED8AE6B-AC48-4DC5-84E0-38927E3DAE9B@w3.org>
To: Brian Kardell <bkardell@gmail.com>
I might be missing something here, but isn’t :anyof() essentially :matches(), :noneof() essentially :not() and :allof() essentially ...chaining of simple selectors (i.e. compound selectors)? 

Note that :not() has been extended in Selectors 4, and now supports compound selectors too [1].

The only use cases I see that this covers are:

1. XOR, by :oneof()
2. Negation of complex selectors
3. Disjunction of complex selectors (as part of a larger selector, otherwise it can be done already with commas)
4. Intersection of complex selectors 

I’m not sure if #1 is really needed, and the example in your blog post isn’t exactly a real use case. #2 and #3 could be useful, and could be solved by allowing complex selectors in :not() and :matches(), no need for new pseudo-classes. However, I’d bet there was a good reason that we didn’t allow this, since it’s obvious from the spec text that it has been considered. #4 could be useful as well, but I’m pretty sure the reasons preventing #2 and #3 would apply to it too.

[1]: http://www.w3.org/TR/selectors4/#negation


Lea Verou
W3C developer relations
http://w3.org/people/all#leahttp://lea.verou.me ✿ @leaverou






On Mar 8, 2013, at 03:39, Brian Kardell wrote:

> A recent discussion about adding Set operations on another list prompted me to discuss something to Tab which I've mulled around (even prollyfilled) in the past and think it's worth proposing...
> 
> CSS selectors operate on _sets_ of elements, but until  recently (:matches/:not) we've had nothing in the way of logical selectors or any language constructs that hinted at set oriented language.   This seems a shame to me as sets and logic gates are some of the most powerful concepts in CS.  The relationship feels natural to me.
> 
> This proposal would require us to get complex selectors inside, but essentially I am proposing some logical combinators like 
> :anyof, :allof, :oneof, :noneof to act as predicates which allow some very rich selection.  Examples/more details in my blog post:
> 
> http://briankardell.wordpress.com/2013/03/07/logical-psuedo-selectors-a-proposal/
> 
> -- 
> Brian Kardell :: @briankardell :: hitchjs.com
Received on Thursday, 14 March 2013 23:19:13 GMT

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