Lab4

[BertLisser]

Exercise 3

crossCheckEls :: Ord a => Set a -> Set a -> Bool
crossCheckEls set1 set2 = subSet setIntersection set1 && subSet setIntersection set2
    where
        setIntersection = intersectionSet set1 set2

must be changed in

testIntersectionSet :: Ord a => Set a -> Set a -> Bool
testIntersectionSet set1 set2 = subSet setIntersection set1 && subSet setIntersection set2
    where
        setIntersection = intersectionSet set1 set2

Exercise 5

crossCheckEls is not needed.
Exercise 5

-- Generates a list of tuples and their inverse to make in symmetrical, then
-- sorts that lits and removes any duplicates.
symClos :: Ord a => Rel a -> Rel a
symClos [] = []
symClos (x:xs) = sort( nub( swap x : x : symClos xs))

is too expensive.
Better

symClos' :: Ord a => Rel a -> Rel a
symClos' [] = []
symClos' (ls@x:xs) =  (swap x) : ls
symClos :: Ord a => Rel a -> Rel a
symClos xs = sort( nub(symClos' xs))