Step by Step solution about How to resolve the algorithm Deal cards for FreeCell step by step in the Haskell programming language

This Haskell code simulates a card dealing process using a specific random number generator to determine the order in which cards are dealt. Here's a detailed explanation of what the code does:

1. Random Number Generation:

   • srnd :: Int32 -> [Int]: This function takes an integer s as input and generates a sequence of pseudo-random integers. It uses a linear congruential generator (LCG) with specific constants to produce the sequence.

2. Card Representation:

   • The code represents a deck of cards as a list of strings. Each string represents a suit (either "C", "D", "H", or "S") followed by a rank (either "A", "2", "3", ..., "10", "J", "Q", or "K").

3. Card Dealing:

   • deal :: Int32 -> [String]: This function simulates the process of dealing cards. It takes an integer s as input, which is used to initialize the random number generator.

4. Core Dealing Logic (ST Monad):

   • The core dealing logic is implemented using the ST monad, which allows for mutable state operations.
   • An array ar is created to represent the deck of cards. It maps each card's position (index) in the deck to its string representation.
   • A list of pairs (n, r) is generated, where n represents the current size of the deck and r represents a random number.
   • For each pair, the following steps are performed:
     • The random number r is used to determine the position j from which a card will be drawn.
     • The card at position j is read from the array ar.
     • The card at the current last position (n - 1) is read from the array ar.
     • The card at position j is replaced with the card from the last position.
     • The card from the last position is returned.
   • This process simulates the movement of cards from the bottom of the deck to the top.

5. Card Display:

   • showCards :: [String] -> IO (): This function takes a list of cards (represented as strings) and displays them on the console. It splits the list of cards into groups of 8 and prints each group on a separate line.

6. Main Function:

   • main :: IO (): This is the main entry point of the program.
   • It gets the command-line arguments, reads the first argument as an integer s, and calls the deal function to simulate the card dealing process for the given s.
   • The resulting list of dealt cards is then displayed using the showCards function.

import Data.Int
import Data.Bits
import Data.List
import Data.Array.ST
import Control.Monad
import Control.Monad.ST
import System.Environment

srnd :: Int32 -> [Int]
srnd = map (fromIntegral . flip shiftR 16) .
       tail . iterate (\x -> (x * 214013 + 2531011) .&. maxBound)

deal :: Int32 -> [String]
deal s = runST (do
    ar <- newListArray (0,51) $ sequence ["A23456789TJQK", "CDHS"]
          :: ST s (STArray s Int String)
    forM (zip [52,51..1] rnd) $ \(n, r) -> do
      let j = r `mod` n
      vj <- readArray ar j
      vn <- readArray ar (n - 1)
      writeArray ar j vn
      return vj)
  where rnd = srnd s

showCards :: [String] -> IO ()
showCards = mapM_ (putStrLn . unwords) .
            takeWhile (not . null) .
            unfoldr (Just . splitAt 8)

main :: IO ()
main = do
  args <- getArgs
  let s = read (head args) :: Int32
  putStrLn $ "Deal " ++ show s ++ ":"
  let cards = deal s
  showCards cards