From 65ffe186acb5f32f0bba07b8ce0eecacbda83bbd Mon Sep 17 00:00:00 2001
From: Ben Sima <ben@bsima.me>
Date: Wed, 8 Aug 2018 19:08:20 -0700
Subject: De-nest rain.bh exercise

---
 rain.bh.hs | 89 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 89 insertions(+)
 create mode 100755 rain.bh.hs

(limited to 'rain.bh.hs')

diff --git a/rain.bh.hs b/rain.bh.hs
new file mode 100755
index 0000000..0133c2b
--- /dev/null
+++ b/rain.bh.hs
@@ -0,0 +1,89 @@
+#!/usr/bin/env stack
+{- stack
+     --nix
+     --resolver lts-11.15
+     --install-ghc
+     runghc
+     --package random
+-}
+
+{-# 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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