CLDR Ticket #10201(accepted data)
Danish collation: thorn should be secondary not tertiary
|Reported by:||markus||Owned by:||markus|
The thorn is tertiary-after th (case-like difference) while most of the other variations are secondary-after their regular bases (as usual for ligatures and such). Unless the Danish sorting standard indicates something about the strength of the thorn difference, it should be secondary.
We have &th<<<þ &TH<<<Þ
Customary would be &th<<þ<<<Þ
It is customary for ligatures and such letter-form variations to trump case & font variations. For example, long-s ſ is secondary-after s; sharp-s ß is secondary-after ss; etc.: http://www.unicode.org/charts/collation/chart_Latin.html
Also, a common way to do case-insensitive matching is to set strength=secondary. With the current rules, that makes th match thorn. With the usual secondary difference, they don't match. Of course, if you also ignore accents (strength=primary), they match either way.
Danish has secondary differences for most of the other near-equivalences (y vs. ü, æ vs. ä, ø vs. ö vs. ő).
Note: Danish å vs. aa is currently also only a tertiary difference. We might consider it at the same time as th vs. þ.
Difference in sort orders:
(ｔｈ uses fullwidth ASCII as one example of other tertiary variants.)
Current thorn with [caseFirst upper]
Customary thorn with [caseFirst upper]