saxon:line-number() ==> xs:integer
saxon:line-number($node as node()) ==> xs:integer
This function returns the line number of a selected node within the XML document (or external entity)
that contains it. If the argument is supplied, it must be a node; if the argument is omitted, the context item is used,
in which case the context item must be a node. If line numbers are not maintained for the current
document, the function returns -1.
To ensure that line numbers are maintained, use the -l (letter ell)
option on the command line.
From release 9.0, the -l option also causes line numbers to be copied from a source document to a result
document when the
xsl:copy-of instruction is applied to a document or element node. For elements
created using other instructions, the line number will reflect the position of the instruction in the stylesheet
or query that caused the element to be created.