SWI-Prolog -- msort/2

Documentation
- Reference manual
  - Built-in Predicates
    - Built-in list operations
      - is_list/1
      - memberchk/2
      - length/2
      - sort/2
      - sort/4
      - msort/2
      - keysort/2
      - predsort/3
- Packages

Availability:built-in

msort(+List, -Sorted)

Equivalent to sort/2, but does not remove duplicates. Raises a type_error if List is a cyclic list or not a list.