The standard library list_mergesort package implements Mergesort on Lists.
It is hard to sort a List efficiently: the lack of constant-time random access means that most fast sort algorithms like Quicksort cannot be used. Mergesort is the major exception. It is the workhorse algorithm when sorting lists.
The list_mergesort package implements the List_Sort API.
The list_mergesort package source code is in src/lib/src/list-mergesort.pkg.
The above information is manually maintained and may contain errors.