Lab 4

[BertLisser]

Ex. 6
This is wrong code. temp is not sorted and with duplicates.

-- Transitive closure of relation, sorted and without duplicates
trClos :: Ord a => Rel a -> Rel a
trClos xs
    | xs /= temp = trClos temp
    | otherwise = xs
    where temp = (xs `union` concat [ concat [ ([a] @@ [b]) | a <- xs, a /= b] | b <- xs])

Solution

trClos :: Ord a => Rel a -> Rel a
trClos xs
    | xs /= temp = trClos temp
    | otherwise = xs
    where temp = (sort.nub) (xs `union` concat [ concat [ ([a] @@ [b]) | a <- xs, a /= b] | b <- xs])