map length (tiers :: [[ Set Bool ]])  =  [1,2,1]

length (list :: [ Set Bool ])  =  4

allUnique (list :: [ Set Bool ])  =  True

ratioRepetitions (list :: [ Set Bool ])  =  0 % 1

tiers :: [Set Bool]  =
  [ [fromList []]
  , [ fromList [False]
    , fromList [True]
    ]
  , [fromList [False,True]]
  ]