On 21/03/2014 15:15, David Sewell wrote:
I wonder how much of the problem (and there is one, at least for
beginning users of XPath/XQuery/XSLT, and it even bites old hands
sometimes) is owing to the fact that the XPath syntax for an axis
step followed by a node type is identical to the syntax for an axis
step followed by a single-argument function.
$node/text()
looks just like
$node/string()
even though the underlying semantics are quite different. I suspect
that mentally one tends to conflate the two. (Applying the
Sapir-Whorf hypothesis to programming languages, i.e. the way a
language encodes things influences the way we think about them.)
David
The single argument function form is of course a lot later (xpath2) than
the text() node step. But actually they can be seen as the same thing.
If I define a user-defined function my:text(n) that returns the text
node children of the input node n
<xsl:function name="my:text">
<xsl:param name="n"/>
<xsl:sequence select="$n/text()"/>
</xsl:function>
then
$node/text()
and
$node/my:text(.)
are the same thing. the only magic part is that user-defined functions
can not default the context node, so the syntax has to be
$node/my:text(.)
rather than
$node/my:text()
Basically all axis steps can be seen as syntactic sugar for functions
that default to the context node and return a sequence of nodes.
David
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