Humble numbers: Difference between revisions

=={{header|Haskell}}==

<lang haskell>import Data.Numbers.Primes (primeFactors)

import Control.Arrow ((&&&))

import Data.List (group)

import Data.Bool (bool)

----------------------HUMBLE NUMBERS-----------------------

humbles :: [Integer]

humbles = filter (all (< 8) . primeFactors) [1 ..]

---------------------------TEST----------------------------

main :: IO ()

main = do

putStrLn "First 50 Humble numbers:"

mapM_ (putStrLn . concat) $

chunksOf 10 $ (justifyRight 4 ' ' . show) <$> take 50 humbles

putStrLn "\nCount of humble numbers for each digit length 1-6:"

mapM_ print $ take 6 $ (head &&& length) <$> group (digitCount <$> humbles)

digitCount :: Integer -> Int

digitCount n =

let go x

| 10 > x = 1

| otherwise = succ (go (div x 10))

in go n

--------------------------DISPLAY--------------------------

chunksOf :: Int -> [a] -> [[a]]

chunksOf n xs =

foldr

(\(x, i) a -> bool (take n (drop i xs) : a) a (rem i n > 0))

[]

(zip xs [0 ..])

justifyRight :: Int -> a -> [a] -> [a]

justifyRight n c = (drop . length) <*> (replicate n c ++)</lang>

{{Out}}

<pre>First 50 Humble numbers:

1 2 3 4 5 6 7 8 9 10

12 14 15 16 18 20 21 24 25 27

28 30 32 35 36 40 42 45 48 49

50 54 56 60 63 64 70 72 75 80

81 84 90 96 98 100 105 108 112 120

Count of humble numbers for each digit length 1-6:

(1,9)

(2,36)

(3,95)

(4,197)

(5,356)

(6,579)</pre>