module Exercise_7 where

import Data.List

{-WETT-}
comp :: Eq b => [(Integer,(a,b))] -> [(Integer,(b,c))] -> [(Integer,(a,c))]
comp xs ys = [(x + y, (a,d))|(x, (a,b)) <- xs, (y,(c,d)) <- ys, b == c]


trancl :: Eq a => [(Integer,(a,a))] -> [(Integer,(a,a))]
trancl xs = filt (sortOn fst (trans xs 4))
    where 
        filt [] = []
        filt ((m,(a,b)):xs) =  if (elem (a,b) (snd (unzip xs)))
            then [(m,(a,b))] ++ (filt [(n,(c,d))| (n,(c,d)) <- xs, (c,d) /= (a,b)])
            else [(m,(a,b))] ++ (filt xs)
        trans xs a = if a == 0 || null (comp xs xs) then xs else trans (filt (sortOn fst (xs ++ (comp xs xs)))) (a-1)
{-TTEW-}