I found this article referencing the O(n) complexity for the 'head . sort' http://apfelmus.nfshost.com/articles/quicksearch.html http://apfelmus.nfshost.com/ar

I found this article referencing the O(n) complexity for the 'head . sort' http://apfelmus.nfshost.com/articles/quicksearch.html http://apfelmus.nfshost.com/articles/quicksearch.html As far as I can understand from the blog and and the cited mailing lists, it works but it requires a carefully coded sorting method, otherwise O(n log n) as expected.