XSLT 2.0 and XPath 2.0 Programmer's Reference, 4th Edition (615 page)
Read XSLT 2.0 and XPath 2.0 Programmer's Reference, 4th Edition Online
Authors: Michael Kay
| Expression | Result |
| resolve-uri(“g”) | “http://a/b/c/g” |
| resolve-uri(“./g”) | “http://a/b/c/g” |
| resolve-uri(“g/”) | “http://a/b/c/g/” |
| resolve-uri(“/g”) | “http://a/g” |
| resolve-uri(“?y”) | “http://a/b/c/?y” |
| resolve-uri(“g?y”) | “http://a/b/c/g?y” |
| resolve-uri(“”) | “http://a/b/c/d;p?q” (but see Note) |
| resolve-uri(“#s”) | “http://a/b/c/d;p”?q#s” (but see Note) |
| resolve-uri(“../g”) | “http://a/b/g” |
RFC 2396 is rather coy in its description of how a relative reference of
“”
(the zero-length string) is supposed to behave, giving a description that only really makes sense in the context of a web browser. RFC 3986 clears this up.
Usage
The most likely place you will need to use the
resolve-uri()
function is in conjunction with the
doc()
function, described on page 750. By default, a relative reference passed to the
doc()
function is resolved relative to the base URI from the static context of the XPath expression. If the relative URI was read from a source document, it makes much more sense to resolve it against the base URI of the node that contained it. The code usually looks something like this:
doc(resolve-uri(@href, base-uri(.)))
See Also
base-uri()
on page 719
doc()
on page 750
escape-uri()
on page 811
static-base-uri()
on page 876
reverse
The
reverse()
function returns a sequence in reverse order. For example,
reverse(1 to 5)
returns the sequence5, 4, 3, 2, 1.
Signature
| Argument | Type | Meaning |
| sequence | item()* | The input sequence |
| Result | item()* | A sequence containing the same items as the input sequence, but in reverse order |
Effect
The result of the function contains exactly the same items as the input sequence, but the order is reversed. The effect is the same as the expression:
for $i in 1 to count($sequence) return
$sequence[count($sequence) - $i + 1]
or if you prefer a recursive formulation:
if (empty($sequence))
then ()
else (reverse(remove($sequence, 1)), $sequence[1])
Examples
| Expression | Result |
| reverse(1 to 5) | 5, 4, 3, 2, 1 |
| reverse(1) | 1 |
| reverse(()) | () |
| reverse(ancestor::*) | A list of ancestor elements, in reverse document order (that is, innermost first) |
See Also
unordered()
on page 901
root
The
root()
function returns the root node of the tree containing a specified start node, or the root of the tree containing the context node.
Signature
| Argument | Type | Meaning |
| start-node (optional) | node()? | A node in the tree whose root is required. If the argument is omitted, it defaults to the context node. It is then an error if the context item is not a node (for example, if it is an atomic value, or if it is undefined). |
| Result | node()? | The root of the tree containing the start node . |
Effect
If the
start-node
argument is supplied and its value is an empty sequence, then the result of the function is an empty sequence.
In other cases, the function returns the root node of the tree containing the
start-node
. The result is the same as the path expression(ancestor-or-self::node())[1]. This node is not necessarily a document node, since it is possible in the XPath 2.0 data model to have elements or other nodes that are parentless. The system follows the parent axis until it finds a node that has no parent, and then it returns that node. If the start node has no parent, then the start node itself is returned as the result of the function.
Examples
| Expression | Result |
| root() | The root node of the tree containing the context node |
| root($x) | The root node of the tree containing the node $x |
| $seq/root() | A sequence containing the root nodes of all the trees containing nodes in $seq , in document order with duplicates removed |
Usage
The effect of the
root()
function, when called with no argument, is very similar to the effect of the expression/. However,/will return the root node of the tree containing the context node only if the root is a document node; in other cases, it reports a runtime error.