module Exercise_7 where

import Data.List
import Data.Ord
  
{-WETT-}
comp :: Eq b => [(Integer,(a,b))] -> [(Integer,(b,c))] -> [(Integer,(a,c))]
comp r s = [(n+m,(a,d))  | (n,(a,b)) <- r , (m,(c,d)) <- s,  b == c  ] 

trancl :: Eq a => [(Integer,(a,a))] -> [(Integer,(a,a))]
trancl ls =  trancl_aux ((length ls) `div` 2) ls  
            where trancl_aux n l = if n == 0 then remDup (sortBy (comparing fst) (ls ++ comp l l)) else trancl_aux (n-1)  (remDup (sortBy (comparing fst) (ls ++ comp l l)))

remDup :: Eq a =>  [(Integer,(a,a))] -> [(Integer,(a,a))]
remDup [] = []
remDup ((n,(a,b)):ls) = (n,(a,b)) : remDup [ (m,(c,d)) |(m,(c,d)) <- ls,  not (a == c && b == d)  ]
{-TTEW-}