lookupx ((t,a):xs) t' | t == t'   = Just a
                      | otherwise = lookupx xs t'
lookupx ((t,a):xs) t' | t == t'   = Just a
                      | otherwise = lookupx xs t'
lookupx ((t,a):xs) t' | t == t'   = Just a
                      | otherwise = lookupx xs t'