Past exam of the year 1 of the computer science course of the University of Oxford / 2014 / Imperative programming / 8 / b / Solution

Keep precisely those elements with no strictly smaller element in the input. Express strictness using the partial order itself, avoiding reliance on Scala reference equality.In a partial order, $y<x$ means $y\le x$ and $x\nleqq y$. ThereforeThe empty set produces the empty set. An incomparable pair is retained in full; a minimal element need not be a least element. At most $O(|X{|}^2)$ order comparisons are needed, and only the supplied F-bounded generic interface is required.