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Added XPath equivalents for :nth-child in the spec

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Yorick Peterse 2014-11-02 23:50:58 +01:00
parent 74f5a10252
commit bb13834e76
1 changed files with 15 additions and 1 deletions
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doc/css_selectors.md
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@ -491,9 +491,23 @@ To summarize:
:nth-child(even) => matches every 2nd element, starting at element 2
:nth-child(odd) => matches every 2nd element, starting at element 1
The corresponding XPath expressions are quite complex and differ based on the
interval argument used. For the various forms the corresponding XPath
expressions are as following:
:nth-child(n) => *[((count(preceding-sibling::*) + 1) mod 1) = 0]
:nth-child(-n) => *[((count(preceding-sibling::*) + 1) mod 1) = 0]
:nth-child(5) => *[count(preceding-sibling::*) = 4]
:nth-child(2n) => *[((count(preceding-sibling::*) + 1) mod 2) = 0]
:nth-child(2n+2) => *[(count(preceding-sibling::*) + 1) >= 2 and (((count(preceding-sibling::*) + 1) - 2) mod 2) = 0]
:nth-child(2n-6) => *[(count(preceding-sibling::*) + 1) >= 2 and (((count(preceding-sibling::*) + 1) - 2) mod 2) = 0]
:nth-child(n+5) => *[(count(preceding-sibling::*) + 1) >= 5 and (((count(preceding-sibling::*) + 1) - 5) mod 1) = 0]
:nth-child(-n+6) => *[((count(preceding-sibling::*) + 1) <= 6) and (((count(preceding-sibling::*) + 1) - 6) mod 1) = 0]
:nth-child(even) => *[((count(preceding-sibling::*) + 1) mod 2) = 0]
:nth-child(odd) => *[(count(preceding-sibling::*) + 1) >= 1 and (((count(preceding-sibling::*) + 1) - 1) mod 2) = 0]
[w3spec]: http://www.w3.org/TR/css3-selectors/
[rfc-2119]: https://www.ietf.org/rfc/rfc2119.txt
[kramdown]: http://kramdown.gettalong.org/
[universal-selector]: #universal-selector
[bnf]: https://en.wikipedia.org/wiki/Backus%E2%80%93Naur_Form
[ragel]: http://www.colm.net/open-source/ragel/