# Haskell Quiz/The Solitaire Cipher/Solution Paul

### From HaskellWiki

< Haskell Quiz | The Solitaire Cipher(Difference between revisions)

(sharpen cat) |
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to_number :: Char -> Int |
to_number :: Char -> Int |
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− | to_number c = (fromEnum c) - (fromEnum 'A') + 1 |
+ | to_number c = fromEnum c - fromEnum 'A' + 1 |

from_number :: Int -> Char |
from_number :: Int -> Char |
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− | from_number n = (toEnum (n - 1 + fromEnum 'A')) |
+ | from_number n = toEnum (n - 1 + fromEnum 'A') |

to_numbers :: String -> [Int] |
to_numbers :: String -> [Int] |
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− | to_numbers s = map to_number s |
+ | to_numbers = map to_number |

cleanse :: String -> String |
cleanse :: String -> String |
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− | cleanse c = (map toUpper) ((filter isAlpha) c) |
+ | cleanse = map toUpper . filter isAlpha |

pad :: Int -> Char -> String -> String |
pad :: Int -> Char -> String -> String |
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− | pad n c s | length s < n = s ++ (replicate (n-length s) c) |
+ | pad n c s | length s < n = s ++ replicate (n-length s) c |

− | pad n c s = s |
+ | pad n c s | otherwise = s |

maybe_split :: String -> Maybe(String,String) |
maybe_split :: String -> Maybe(String,String) |
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maybe_split [] = Nothing |
maybe_split [] = Nothing |
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maybe_split s | w == "" = Just (pad 5 'X' s,w) |
maybe_split s | w == "" = Just (pad 5 'X' s,w) |
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− | | True = Just (take 5 s, w) |
+ | | otherwise = Just (take 5 s, w) |

where w = drop 5 s |
where w = drop 5 s |
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quintets :: String -> [String] |
quintets :: String -> [String] |
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− | quintets s = (unfoldr maybe_split) s |
+ | quintets = unfoldr maybe_split |

data Suit = Clubs | Diamonds | Hearts | Spades | A | B |
data Suit = Clubs | Diamonds | Hearts | Spades | A | B |
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Line 39: | Line 39: | ||

show_suit :: Suit -> String |
show_suit :: Suit -> String |
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− | show_suit s = (take 1) (show s) |
+ | show_suit = head . show |

data Face = Ace | Two | Three | Four | Five | Six | Seven |
data Face = Ace | Two | Three | Four | Five | Six | Seven |
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Line 46: | Line 46: | ||

show_face :: Face -> String |
show_face :: Face -> String |
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− | show_face f = [head (drop (fromEnum f) "A23456789TJQK$")] |
+ | show_face f = ["A23456789TJQK$" !! fromEnum f] |

− | data Card = Cd Suit Face |
+ | data Card = Cd {suit :: Suit, face :: Face} |

deriving Eq |
deriving Eq |
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− | |||

− | suit :: Card -> Suit |
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− | suit (Cd s _) = s |
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− | |||

− | face :: Card -> Face |
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− | face (Cd _ f) = f |
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instance Enum Card where |
instance Enum Card where |
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− | toEnum 53 = (Cd B Joker) |
+ | toEnum 53 = Cd B Joker |

− | toEnum 52 = (Cd A Joker) |
+ | toEnum 52 = Cd A Joker |

− | toEnum n = let d = n `divMod` 13 |
+ | toEnum n = let (q,r) = n `divMod` 13 |

− | in Cd (toEnum (fst d)) (toEnum (snd d)) |
+ | in Cd (toEnum q) (toEnum r) |

fromEnum (Cd B Joker) = 53 |
fromEnum (Cd B Joker) = 53 |
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fromEnum (Cd A Joker) = 52 |
fromEnum (Cd A Joker) = 52 |
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Line 67: | Line 61: | ||

instance Show Card where |
instance Show Card where |
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− | show c = (show_face (face c)) ++ (show_suit (suit c)) |
+ | show c = show_face (face c) ++ show_suit (suit c) |

value :: Card -> Int |
value :: Card -> Int |
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value (Cd B Joker) = 53 |
value (Cd B Joker) = 53 |
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value c = fromEnum c + 1 |
value c = fromEnum c + 1 |
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− | |||

− | drop_tail :: [a] -> [a] |
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− | drop_tail l = reverse (drop 1 (reverse l)) |
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split_on_elem :: Eq a => a -> [a] -> ([a],[a]) |
split_on_elem :: Eq a => a -> [a] -> ([a],[a]) |
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− | split_on_elem x l | x == head l = ([],drop 1 l) |
+ | split_on_elem x l | x == head l = ([],tail l) |

− | split_on_elem x l | x == head (reverse l) = (drop_tail l, []) |
+ | split_on_elem x l | x == last l = (init l, []) |

− | split_on_elem x l | elemIndex x l == Nothing = error "Can't split a list on an element that isn't present." |
+ | split_on_elem x l | otherwise = case elemIndex x l of |

− | split_on_elem x l = let y = fromJust(elemIndex x l) |
+ | Nothing -> error "Can't split a list on an element that isn't present." |

− | in (take y l, drop (y+1) l) |
+ | Just y -> (take y l, drop (y+1) l) |

swap_down :: Card -> [Card] -> [Card] |
swap_down :: Card -> [Card] -> [Card] |
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− | swap_down x deck | (fst halves) == [] = (head (snd halves)):(x:(drop 1 (snd halves))) |
+ | swap_down x deck | null xs = head ys:x:tail ys |

− | | (snd halves) == [] = (head (fst halves)):x:(drop 1 (fst halves)) |
+ | | null ys = head xs:x:tail xs |

− | | True = (fst halves) ++ ((head (snd halves)):x:(drop 1 (snd halves))) |
+ | | otherwise = xs ++ (head ys:x:tail ys) |

− | where halves = split_on_elem x deck |
+ | where (xs,ys) = split_on_elem x deck |

move_a :: [Card] -> [Card] |
move_a :: [Card] -> [Card] |
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Line 100: | Line 91: | ||

triple_cut :: Card -> Card -> [Card] -> [Card] |
triple_cut :: Card -> Card -> [Card] -> [Card] |
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− | triple_cut x y deck | slot_x < slot_y = (snd (split_y)) ++ (x:(from_m_to_n slot_x slot_y deck)) ++ (y:(fst split_x)) |
+ | triple_cut x y deck | slot_x < slot_y = y2 ++ (x:(from_m_to_n slot_x slot_y deck)) ++ (y:x1) |

− | | slot_x > slot_y = (snd (split_x)) ++ (y:(from_m_to_n slot_y slot_x deck)) ++ (x:(fst split_y)) |
+ | | slot_x > slot_y = x2 ++ (y:(from_m_to_n slot_y slot_x deck)) ++ (x:y1) |

− | where slot_x = fromJust(elemIndex x deck) |
+ | where Just slot_x = elemIndex x deck |

− | slot_y = fromJust(elemIndex y deck) |
+ | Just slot_y = elemIndex y deck |

− | split_x = split_on_elem x deck |
+ | (x1,x2) = split_on_elem x deck |

− | split_y = split_on_elem y deck |
+ | (y1,y2) = split_on_elem y deck |

triple_cut_a_b :: [Card] -> [Card] |
triple_cut_a_b :: [Card] -> [Card] |
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Line 111: | Line 102: | ||

count_cut :: [Card] -> [Card] |
count_cut :: [Card] -> [Card] |
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− | count_cut deck = (drop_tail (drop val deck)) ++ (take val deck) ++ [bottom_card] |
+ | count_cut deck = drop (val-1) deck ++ take val deck ++ [bottom_card] |

− | where bottom_card = head (reverse deck) |
+ | where bottom_card = last deck |

val = value (bottom_card) |
val = value (bottom_card) |
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evaluate :: [Card] -> Int |
evaluate :: [Card] -> Int |
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− | evaluate deck = value (head (drop (value(head(deck))) deck)) |
+ | evaluate deck = value (deck !! value (head deck)) |

compute :: [Card] -> (Int,[Card]) |
compute :: [Card] -> (Int,[Card]) |
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− | compute deck | val == 53 = compute (x) |
+ | compute deck | val == 53 = compute x |

− | | True = ((val `mod` 26), x) |
+ | | otherwise = (val `mod` 26, x) |

− | where x = count_cut ( triple_cut_a_b ( move_b ( move_a ( deck )))) |
+ | where x = count_cut $ triple_cut_a_b $ move_b $ move_a $ deck |

val = evaluate x |
val = evaluate x |
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Line 129: | Line 120: | ||

encode_ :: String -> [Card] -> String |
encode_ :: String -> [Card] -> String |
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encode_ [] _ = [] |
encode_ [] _ = [] |
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− | encode_ (s:ss) deck = let c = compute(deck) |
+ | encode_ (s:ss) deck = let (a,b) = compute deck |

− | in (from_number(wrap_zero ((fst c + (to_number s)) `mod` 26))):(encode_ ss (snd c)) |
+ | in from_number(wrap_zero ((a + to_number s) `mod` 26)):encode_ ss b |

decode :: String -> String |
decode :: String -> String |
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Line 137: | Line 128: | ||

decode_ :: String -> [Card] -> String |
decode_ :: String -> [Card] -> String |
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decode_ [] _ = [] |
decode_ [] _ = [] |
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− | decode_ (s:ss) deck = let c = compute(deck) |
+ | decode_ (s:ss) deck = let (a,b) = compute deck |

− | in (from_number(wrap_zero ((26 + (to_number s) - fst c) `mod` 26))):(decode_ ss (snd c)) |
+ | in from_number(wrap_zero ((26 + to_number s - a) `mod` 26)):decode_ ss b |

wrap_zero :: Int -> Int |
wrap_zero :: Int -> Int |

## Latest revision as of 19:33, 21 February 2010

-- Solution to Ruby Quiz problem #1 -- Paul Brown (paulrbrown@gmail.com) -- http://mult.ifario.us/ import Char import List import Maybe to_number :: Char -> Int to_number c = fromEnum c - fromEnum 'A' + 1 from_number :: Int -> Char from_number n = toEnum (n - 1 + fromEnum 'A') to_numbers :: String -> [Int] to_numbers = map to_number cleanse :: String -> String cleanse = map toUpper . filter isAlpha pad :: Int -> Char -> String -> String pad n c s | length s < n = s ++ replicate (n-length s) c pad n c s | otherwise = s maybe_split :: String -> Maybe(String,String) maybe_split [] = Nothing maybe_split s | w == "" = Just (pad 5 'X' s,w) | otherwise = Just (take 5 s, w) where w = drop 5 s quintets :: String -> [String] quintets = unfoldr maybe_split data Suit = Clubs | Diamonds | Hearts | Spades | A | B deriving (Enum, Show, Bounded, Eq) show_suit :: Suit -> String show_suit = head . show data Face = Ace | Two | Three | Four | Five | Six | Seven | Eight | Nine | Ten | Jack | Queen | King | Joker deriving (Enum, Show, Bounded, Eq) show_face :: Face -> String show_face f = ["A23456789TJQK$" !! fromEnum f] data Card = Cd {suit :: Suit, face :: Face} deriving Eq instance Enum Card where toEnum 53 = Cd B Joker toEnum 52 = Cd A Joker toEnum n = let (q,r) = n `divMod` 13 in Cd (toEnum q) (toEnum r) fromEnum (Cd B Joker) = 53 fromEnum (Cd A Joker) = 52 fromEnum c = 13* fromEnum(suit c) + fromEnum(face c) instance Show Card where show c = show_face (face c) ++ show_suit (suit c) value :: Card -> Int value (Cd B Joker) = 53 value c = fromEnum c + 1 split_on_elem :: Eq a => a -> [a] -> ([a],[a]) split_on_elem x l | x == head l = ([],tail l) split_on_elem x l | x == last l = (init l, []) split_on_elem x l | otherwise = case elemIndex x l of Nothing -> error "Can't split a list on an element that isn't present." Just y -> (take y l, drop (y+1) l) swap_down :: Card -> [Card] -> [Card] swap_down x deck | null xs = head ys:x:tail ys | null ys = head xs:x:tail xs | otherwise = xs ++ (head ys:x:tail ys) where (xs,ys) = split_on_elem x deck move_a :: [Card] -> [Card] move_a deck = swap_down (Cd A Joker) deck move_b :: [Card] -> [Card] move_b deck = swap_down (Cd B Joker) (swap_down (Cd B Joker) deck) from_m_to_n :: Int -> Int -> [a] -> [a] from_m_to_n m n l | m < n = take (n-m-1) (drop (m+1) l) | n < m = take (m-n-1) (drop (n+1) l) triple_cut :: Card -> Card -> [Card] -> [Card] triple_cut x y deck | slot_x < slot_y = y2 ++ (x:(from_m_to_n slot_x slot_y deck)) ++ (y:x1) | slot_x > slot_y = x2 ++ (y:(from_m_to_n slot_y slot_x deck)) ++ (x:y1) where Just slot_x = elemIndex x deck Just slot_y = elemIndex y deck (x1,x2) = split_on_elem x deck (y1,y2) = split_on_elem y deck triple_cut_a_b :: [Card] -> [Card] triple_cut_a_b deck = triple_cut (Cd A Joker) (Cd B Joker) deck count_cut :: [Card] -> [Card] count_cut deck = drop (val-1) deck ++ take val deck ++ [bottom_card] where bottom_card = last deck val = value (bottom_card) evaluate :: [Card] -> Int evaluate deck = value (deck !! value (head deck)) compute :: [Card] -> (Int,[Card]) compute deck | val == 53 = compute x | otherwise = (val `mod` 26, x) where x = count_cut $ triple_cut_a_b $ move_b $ move_a $ deck val = evaluate x encode :: String -> String encode s = encode_ (concat (quintets (cleanse s))) [(Cd Clubs Ace) .. (Cd B Joker)] encode_ :: String -> [Card] -> String encode_ [] _ = [] encode_ (s:ss) deck = let (a,b) = compute deck in from_number(wrap_zero ((a + to_number s) `mod` 26)):encode_ ss b decode :: String -> String decode s = decode_ s [(Cd Clubs Ace) .. (Cd B Joker)] decode_ :: String -> [Card] -> String decode_ [] _ = [] decode_ (s:ss) deck = let (a,b) = compute deck in from_number(wrap_zero ((26 + to_number s - a) `mod` 26)):decode_ ss b wrap_zero :: Int -> Int wrap_zero 0 = 26 wrap_zero x = x