How to implement a custom sorting algorithm in Prolog :
sort(List, Sorted) :-
quicksort(List, [], Sorted).
quicksort([], Acc, Acc).
quicksort([H|T], Acc, Sorted) :-
pivoting(H, T, L1, L2),
quicksort(L1, Acc, Sorted1),
quicksort(L2, [H|Sorted1], Sorted).
pivoting(H, T, L1, L2) :-
choose_pivot(H, T, Pivot),
partition(T, Pivot, L1, L2).
choose_pivot(H, T, Pivot) :-
length(T, N),
select(N div 2, T, Pivot).
partition(List, Pivot, Smaller, Larger) :-
smaller_than(Pivot, List, Smaller),
append(Smaller, [Pivot], List1),
not(smaller_than(Pivot, List1)),
append(List1, Larger, List).
smaller_than(Pivot, [H|T], Smaller) :-
H < Pivot,
Smaller = [H|T].
smaller_than(Pivot, [], Smaller).​
This code implements a quicksort algorithm in Prolog. The
sort/3 predicate takes a list as input and returns a sorted list as output. The
quicksort/3 predicate recursively sorts the list by choosing a pivot element and partitioning the list into two smaller lists, one containing elements smaller than the pivot and the other containing elements larger than the pivot. The
pivoting/3 predicate chooses a pivot element by randomly selecting an element from the list. The
partition/3 predicate partitions the list into two smaller lists based on the pivot element. The
smaller_than/3 predicate checks if an element is smaller than a pivot element.
