On 10 Jan 2014, at 17:05, Eliot Kimber <ekimber(_at_)rsicms(_dot_)com> wrote:
In the context of writing an XSLT to generate DTD syntax from RNGs (for
DITA 1.3) I discovered that for-each results in whitespace being emitted
for each iteration. This came as a surprise. Reading the spec it says,
under clause 7, Repetition:
"For each item in the input sequence, evaluating the sequence constructor
<http://www.w3.org/TR/xslt20/#dt-sequence-constructor> produces a sequence
of items (see 5.7 Sequence Constructors
<http://www.w3.org/TR/xslt20/#sequence-constructors>). These output
sequences are concatenated; ...
I understand "These output sequences are concatenated” to mean that string
concatenation rules are applied, which explains the white space.
No, this is a concatenation of two or more sequences to produce a single
sequence. No whitespace is added at this point.
My question: why is for-each defined in this way?
It isn't.
I tested this with this little XSLT transform:
<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform";
xmlns:xs="http://www.w3.org/2001/XMLSchema";
xmlns:xd="http://www.oxygenxml.com/ns/doc/xsl";
exclude-result-prefixes="xs xd"
version="2.0">
<xsl:output method="text"/>
<xsl:template name="test-for-each">
<xsl:variable name="strings" select="('one', 'two', 'three', 'four')"/>
value-of $strings=<xsl:value-of select="$strings"/>
for $str in $strings return concat('/', $str, '/')=<xsl:sequence
select="for $str in $strings return concat('/', $str, '/')"/>
string-join($strings, '')=<xsl:sequence select="string-join($strings,
'')"/>
for-each over strings: "<xsl:for-each select="$strings">
<xsl:sequence select="concat('/',.,'/')"/>
</xsl:for-each>"
</xsl:template>
</xsl:stylesheet>
Which produces this output using Saxon 9.5.1.2:
value-of $strings=one two three four
for $str in $strings return concat('/', $str, '/')=/one/ /two/ /three/
/four/
string-join($strings, '')=onetwothreefour
for-each over strings: "/one/ /two/ /three/ /four/"
The whitespace is being added as part of the process of constructing your final
result tree from a sequence of strings. The result tree is constructed as a
document node, following the rules of 5.7.1 Constructing Complex Content
http://www.w3.org/TR/2009/PER-xslt20-20090421/#constructing-complex-content
or equivalently the rules applied by the Serializer
http://www.w3.org/TR/xslt-xquery-serialization/#serdm
The simplest way to avoid the space separation is to construct text nodes
rather than strings, which happens if you replace xsl;sequence by xsl:value-of
in
<xsl:sequence select="concat('/',.,'/')"/>
Michael Kay
Saxonica
I see that the for-each result is consistent with the flowr expression.
Is my analysis correct that the only way to construct a string with no
extra whitespace using a loop is to use string-join() as in my test case?
For my DTD-generation application that would mean using the for-each loop
to construct a sequence of strings and then using string-join on the
sequence to avoid additional whitespace. Of course I can simply account
for the space inserted by the concatenation and get the correct indention
and keep my code a bit simpler.
Cheers,
Eliot
--
Eliot Kimber
Senior Solutions Architect
"Bringing Strategy, Content, and Technology Together"
Main: 512.554.9368
www.reallysi.com
www.rsuitecms.com
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