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#! /usr/bin/env nix-shell
#! nix-shell -p "haskellPackages.ghcWithPackages (pkgs: [pkgs.random])" -i runghc
{-# OPTIONS_GHC -Wall #-}
{-# LANGUAGE TypeSynonymInstances #-}
{-# LANGUAGE FlexibleInstances #-}
{-
Problem: Create a string array containing a representation of the 52 cards in a
standard deck, and then a second array that shuffles the 52 cards.
Start with two string arrays of the cards and suits:
Cards: 2, 3, 4, 5, 6, 7, 8, 9, 10, J, K, Q, A
Suits: Clubs, Diamonds, Aces, Spades
-}
import System.Random
import Control.Monad
import Control.Applicative
data Name
= Two
| Three
| Four
| Five
| Six
| Seven
| Eight
| Nine
| Ten
| Jack
| King
| Queen
| Ace
deriving (Show, Enum, Bounded)
names :: [Name]
names = [ Two .. ]
data Suit
= Club
| Diamond
| Heart
| Spade
deriving (Show, Enum, Bounded)
suits :: [Suit]
suits = [ Club .. ]
type Card = (Name, Suit)
instance Random Suit where
randomR (a, b) g =
case randomR (fromEnum a, fromEnum b) g of
(x, g') -> (toEnum x, g')
random g = randomR (minBound, maxBound) g
instance Random Name where
randomR (a, b) g =
case randomR (fromEnum a, fromEnum b) g of
(x, g') -> (toEnum x, g')
random g = randomR (minBound, maxBound) g
-- Dot product is same as 'liftA2 (,)'
allCards :: [Card]
allCards = liftA2 (,) names suits
shuffle' :: [Card] -> _
shuffle' (i:is) xs = (last firsts) : shuffle' is (init firsts ++ rest)
where (firsts, rest) = splitAt (i `mod` length xs) xs
shuffle g xs = shuffle (randoms g) xs
main :: IO [()]
main = do
g <- getStdGen
let namesLength = length names
let randomNames = map fromEnum $ take namesLength $ randomRs (0, namesLength-1) g
let suitsLength = length suits
let randomSuits = map fromEnum $ take suitsLength $ randomRs (0, suitsLength-1) g
sequence $ map (putStrLn.show) $ liftA2 (,) randomNames randomSuits
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