On 12.04.2010 11:37, James Cummings wrote:
<xsl:for-each-group select="$sep/node()"
group-adjacent="boolean(self::tei:seg[(_at_)type='sep'])">
This groups the nodes in the variable you've created by the boolean
(so the truth or falsehood of whether the pattern matches? I didn't
know you could do that in a group-* pattern) of the existence of the
segs you've created on tei:seg/text() which mark the whitespace.
There are two flavours of grouping conditions: patterns and expressions.
group-starting/ending-with require patterns while group-by and
group-adjacent accept any XPath expression. The latter are being applied
to each item of the so-called population in order to calculate grouping
keys, the former match specific nodes in the population that will lead
or terminate a group.
For all but the nodes marked-up as WS in our example, evaluating
self::tei:seg[(_at_)type='sep'] yields the empty sequence. Since the empty
sequence cannot be used as a grouping key for group-adjacent [1], its
boolean value is calculated, which is false for empty sequences [2]. I
could have used empty() instead of boolean() which would just flip each
node's true()/false() key. In this case, I would have to swap the "when
current-grouping-key" and the "otherwise" actions accordingly, or
test="not(current-grouping-key())".
In the word wrap example, it's a matter of taste whether to use
group-starting-with or group-adjacent. But try to tackle the
group-adjacent example given in the spec [3] using group-starting-with
(or group-ending-with), and you'll find yourself writing all kinds of
complicated lookaheads and lookbehinds that for-each-group promised to
liberate you from. The same holds for trying to solve
group-starting-with problems using group-adjacent. There's a reason THey
created all 4 forms of for-each-group. And THey saw it was good.
Gerrit
[1] http://www.w3.org/TR/xslt20/#err-XTTE1100
[2] http://www.w3.org/TR/xpath-functions/#func-boolean
[3] http://www.w3.org/TR/xslt20/#d5e21264
<xsl:choose>
<xsl:when test="current-grouping-key()">
<xsl:value-of select="current-group()" />
</xsl:when>
When it is one of those whitespace segs, then just put out the value
of the whitespace, temporary element vanishes.
<xsl:otherwise>
<w xmlns="http://www.tei-c.org/ns/1.0";>
<xsl:apply-templates select="current-group()"/>
</w>
</xsl:otherwise>
Otherwise, wrap it in a word element.
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