import System.Random (newStdGen, randomRs)

dataBinCounts :: [Float] -> [Float] -> [Int]
dataBinCounts thresholds range =
  zipWith
    (-)
    (xs <> [sampleSize])
    (0 : xs)
  where
    sampleSize = length range
    xs =
      (-) sampleSize . length
        . flip filter range
        . (<)
        <$> thresholds

--------------------------- TEST -------------------------
main :: IO ()
main = do
  g <- newStdGen
  let fractions = recip <$> [5 .. 11] :: [Float]
      expected = fractions <> [1 - sum fractions]
      actual =
        (/ 1000000.0) . fromIntegral
          <$> dataBinCounts
            (scanl1 (+) expected)
            (take 1000000 (randomRs (0, 1) g))
      piv n x = take n (x <> repeat ' ');

  putStrLn "       expected     actual"
  mapM_ putStrLn $
    zipWith3
      ( \l s c ->
          piv 7 l
            <> (piv 13 (show s) <> piv 12 (show c))
      )
      [ "aleph",
        "beth",
        "gimel",
        "daleth",
        "he",
        "waw",
        "zayin",
        "heth"
      ]
      expected
      actual