saxon:pedigree
Given a map or array that was obtained by downward selection within a tree of maps and arrays
(such as might be obtained by parsing JSON), and that was marked for tracking of such selections
using the saxon:with-pedigree()
function, the saxon:pedigree()
function
returns a map containing information about the containing map or array in this tree, and
the key or index used to select it within its immediately containing map or array.
pedigree($in as function(*)) ➔ tuple(container: function(*), key: anyAtomicType?, index: xs:integer?)?
Arguments | |||
| $in | function(*) | The input map or array |
Result | tuple(container: function(*), key: anyAtomicType?, index: xs:integer?)? |
Namespace
http://saxon.sf.net/
Saxon availability
Requires Saxon-PE or Saxon-EE. Implemented since Saxon 9.9.
Notes on the Saxon implementation
Available since Saxon 9.9.
Details
If the supplied value is a map or array that has pedigree information by virtue of the fact
that it was obtained by downward selection from a map or array that retains pedigree information,
the pedigree()
function returns information about the containing map or array from
which it was selected.
The result of the function is a map. There is always an entry with the key "container"
,
whose value is the containing map or array (or an empty sequence, if we are at the root of the tree).
If the container is a map, there will also be an entry with key "key"
whose value is
the key of this map/array within the containing map. If the container is an array, there will also
be an entry with key "index"
whose value is the 1-based index of this map/array within
the containing array.
If the supplied argument has no pedigree information, the result is an empty sequence.
For example, given the input:
let $M := map{ "roman": map{ "min":1, "max":10, "codes":map{"i":1, "ii":2, "iii":3, "iv":4, "v":5, "vi":6, "vii":7, "viii":8, "ix":9, "x":10} }, "alpha": map{ "min":1, "max":26, "codes":map{"a":1, "b":2, "c":3, "d":4, "e":5, "f":6, "g":7, "h":8, "i":9, "j":10} } } let $augmentedMap := $M => saxon:with-pedigree() let $romanCodes := $augmentedMap?roman?codes return ....Then ($romanCodes => saxon:pedigree())?container?max
returns 10.
The function is particularly useful when using xsl:apply-templates
to process JSON structures
recursively. For example, it becomes possible to write a template rule such as:
Which matches a map (or array) whose key value in its parent map is "roman".
See also the saxon:deep-update extension instruction, which makes use of pedigree information internally.