query the depth of the lowest node?

[Phlip]

xmlists:

Here's a chestnut from graph theory:

What's the minimum XPath(s) - hence the most efficient way - to query the depth
of the lowest node?

All I can think of is calling count(ancestor::*) on every node...

 

[Martin Honnen]

What's the minimum XPath(s) - hence the most efficient way - to query
the depth of the lowest node?

All I can think of is calling count(ancestor::*) on every node...

With XQuery 1.0 or XPath 2.0 you can do
max(for $el in descendant::* return count($el/ancestor-or-self::*))
That assumes you are interested in element nodes but could obviously be
changed to select other node types.

 

[Martin Honnen]

With XQuery 1.0 or XPath 2.0 you can do
max(for $el in descendant::* return count($el/ancestor-or-self::*))

max(for $el in descendant::*[not(*)] return count($el/ancestor-or-self::*))

should be slightly more efficient.

 

[Phlip]

max(for $el in descendant::*[not(*)] return count($el/ancestor-or-self::*))

While I go smack around the author of Nokogiri to let me return a count instead
of a nodeset...

Does the extant libxml2 do XPath 2.0? And can anyone think of a version that
returns a nodeset?

Until then, I will just use 'descendant::*[not(*)]' to get a nodeset with each
leaf node, then use 'count(ancestor-or-self::*)'. That's better than ON time,
because it's just On where n is the number of leaves...

 

[Phlip]

Until then, I will just use 'descendant::*[not(*)]' to get a nodeset

with each leaf node, then use 'count(ancestor-or-self::*)'. That's
better than ON time, because it's just On where n is the number of
leaves...

def maximum_depth
@builder.doc.xpath('descendant::*[not(*)]').
map{|e| e.xpath('ancestor-or-self::*').length }.
sort.last
end

Yup worked like a charm the first time. Thanks, guys!