[boost] [sorting] What are the most complicated sorting problems?

Hi. Since people want the sorting library to have something that the standard library sorts do not offer, I would like to know the most complicated sorting situations that user have encountered (like sort by name, and then first three digits of phone number, and if the sum of the first three digits of the phone number is less than 10, sort by the second 4 digits of the phone number). I ask this because radixsort and radix quicksort are able to do those sorts, but I need input from users to add features. Also, even if you do not have any complicated sorts, ideas in general would help.