RosettaCodeData/Task/Self-numbers/Haskell/self-numbers.hs

26 lines
807 B
Haskell

import Control.Monad (forM_)
import Text.Printf
selfs :: [Integer]
selfs = sieve (sumFs [0..]) [0..]
where
sumFs = zipWith (+) [ a+b+c+d+e+f+g+h+i+j
| a <- [0..9] , b <- [0..9]
, c <- [0..9] , d <- [0..9]
, e <- [0..9] , f <- [0..9]
, g <- [0..9] , h <- [0..9]
, i <- [0..9] , j <- [0..9] ]
-- More idiomatic list generator is about three times slower
-- sumFs = zipWith (+) $ sum <$> replicateM 10 [0..9]
sieve (f:fs) (n:ns)
| n > f = sieve fs (n:ns)
| n `notElem` take 81 (f:fs) = n : sieve (f:fs) ns
| otherwise = sieve (f:fs) ns
main = do
print $ take 50 selfs
forM_ [1..8] $ \i ->
printf "1e%v\t%v\n" (i :: Int) (selfs !! (10^i-1))