[XSL-LIST Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] RE: mixed content grouping by whitespace
I never fully understood why in > g-s-w/g-e-w groupings the population needs to be all nodes > and not arbitrary sequences. I wonder whether it is because > someone insisted that g-s-w/g-e-w conditions need to be > patterns and hencefore the population need to be nodes, or > whether it was the other way round. Maybe it is as it is for > "historical reasons". Or maybe they thought: if we permit an > arbitrary expression as g-s/e-w condition then we must check > that an effective boolean value may be calculated for this > expression, because it should be a yes/no decision whether a > given item starts/ends a group. Maybe they found that a > pattern that either matches or not is a more clear-cut and > comprehensible binary criterion than arcane EBV semantics, at > least for the common case of grouping nodes. All very good questions. All the places in the language where we apply a boolean test to a specific node are done by patterns, and I guess that's why it was done here: it would be odd to do one thing in xsl:number, and a different thing in xsl:for-each-group. I don't remember a big debate about it. In retrospect it would be nice if the bifurcation between expressions and patterns hadn't happened, and everywhere patterns are used we had instead used an expression evaluated with the target node as context item, taking its effective boolean value. I suspect people wanted to write match="section/head" to make it CSS-like, but I think one could achieve the same with a (pseudo-?) function: match="pattern(section/head)", which could then be used in XPath expressions anywhere, for example <xsl:when test="pattern(section/head)". Integration with types would also have been nice: <xsl:param name="in" as="pattern(section/head)"/>. Sadly, though, language decisions once made cannot easily be improved in this way. Regards, Michael Kay http://www.saxonica.com/ http://twitter.com/michaelhkay
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