Subject: RE: [xsl] positional predicates in XPath vs XQL From: "Michael Kay" <michael.h.kay@xxxxxxxxxxxx> Date: Sat, 24 Nov 2001 11:04:16 -0000 |
No, The XPath query /section/para[1] retrieves the first para element of every section. What made you think otherwise? Mike Kay > -----Original Message----- > From: owner-xsl-list@xxxxxxxxxxxxxxxxxxxxxx > [mailto:owner-xsl-list@xxxxxxxxxxxxxxxxxxxxxx]On Behalf Of Howard Katz > Sent: 23 November 2001 23:36 > To: XSL-List@xxxxxxxxxxxxxxxxxxxxxx > Subject: [xsl] positional predicates in XPath vs XQL > > > I'm implementing an engine that evaluates XPath. I'm > currently working on > the part of the engine that implements positional predicates. I've > previously worked this out for location paths in XQL, but I think the > semantics are different in the two languages and want to make sure I > understand the differences. > > In XQL if you say (pretending for the moment that positions > start from 1 as > they do in XPath, rather than 0): > > /section/para[ 1 ] > > and you have a tree that looks like this: > > 1 section > 2 para > 3 para > 4 section > 5 para > 6 section > 7 para > 8 para > 9 para > > you'll get back this nodeset: > > <2>, <5>, <7> > > You can paraphrase this XQL query as saying, "Give me back > the 1st child > node of each <section> element." Similarly, "/section/para[ 2 > ]" returns > <3>, <8>, and if you say "/section/para[ 3 ]", you get back > the single node, > <9>. > > To my understanding, the same location path in XPath only > returns a single > node, <2>. Is my understanding correct? > > Howard > > > > > > > XSL-List info and archive: http://www.mulberrytech.com/xsl/xsl-list > XSL-List info and archive: http://www.mulberrytech.com/xsl/xsl-list
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