Htirage/Draw.hs

   1 -- | Tirages.
   2 module Htirage.Draw where
   3
   4 import Htirage.Bits
   5 import Htirage.Combin
   6
   7 -- | @draw1 xs bs@ retourne un choix parmi 'xs' déterminé par l’entropie 'bs'.
   8 draw1 :: [a] -> [Bool] -> a
   9 draw1 xs bs = xs !! fromInteger (randomIntegerOfBits (toInteger (length xs - 1)) bs)
  10
  11 -- | @drawMany xs k bs@ retourne 'k' choix (sans répétition) parmi 'xs'
  12 -- déterminés par l’entropie 'bs'.
  13 drawMany :: [a] -> Integer -> [Bool] -> [a]
  14 drawMany xs k bs = (fromInteger <$> combinOfRank n k r) `permute` xs
  15         where n = toInteger (length xs)
  16               r = randomIntegerOfBits ((n`nCk`k) - 1) bs