themselves rather than any relatives of theirs.
This patch is useful for (among other things) constructing blogging
-systems where leaf nodes are organized hierarchically; using has_child,
+systems where leaf nodes are organized hierarchically; using `has_child`,
you can inline only leaf nodes and ignore "intermediate" nodes.
-match_relative can be used recursively to match properties of arbitrary
+`match_relative` can be used recursively to match properties of arbitrary
complexity: "show me all the pages who have children called foo that
have children called blah". I'm not sure what use it is, though.
+
+package IkiWiki::PageSpec;
+
-+sub match_relative($$;@) { #{{{
++sub match_relative($$;@) {
+ my $parent = shift;
+ my $spec = shift;
+ my %params = @_;
+ }
+ }
+ return IkiWiki::FailReason->new("$parent can't match $spec against anything");
-+} #}}}
++}
+
-+sub match_has_child($$;@) { #{{{
++sub match_has_child($$;@) {
+ my $page = shift;
+ my $childname = shift;
+ my $spec;
-+ if ($childname) { #{{{
++ if ($childname) {
+ $spec = "$page/$childname or $page/*/$childname";
-+ } #}}}
-+ else { #{{{
++ }
++ else {
+ $spec = "$page/*";
-+ } #}}}
++ }
+
+ return match_relative($page, $spec, @_);
-+} #}}}
++}
+
+1
-</pre>
\ No newline at end of file
+</pre>
+
+[[!tag patch]]
+
+> This looks really interesting. It reminds me of [[!wikipedia XPath]] and its conditionals.
+> Those might actually work well adapted to pagespecs. For instance, to write
+> "match any page with a child blah", you could just write *[blah] , or if you
+> don't want to use relative-by-default in the conditionals, *[./blah].
+> -- [[JoshTriplett]]
+
+> And it [[!taglink also_reminds_me|pagespec_in_DL_style]] of [[!wikipedia description logics]]: of course, given the relation `subpage` one could write a description-logic-style formula which would define the class of pages that are ("existentially") in a given relation (`subpage` or `inverse(subpage)*subpage`) to a certain other class of pages (e.g., named "blah") ("existentially" means there must exist a page, e.g., named "blah", which is in the given relation to the candidate).
+
+> Probably the model behind XPath is similar (although I don't know enough to say this definitely).--Ivan Z.