1 files changed, 24 insertions, 0 deletions
diff --git a/Haskell-book/11/Cipher.hs b/Haskell-book/11/Cipher.hs
new file mode 100644
index 0000000..92e0e7d
--- /dev/null
+++ b/Haskell-book/11/Cipher.hs
@@ -0,0 +1,24 @@
+module Cipher where
+
+import Data.Char
+import Data.List
+
+decode :: (Char, Int) -> Char
+decode (x, y) =  chr ((mod ((ord x) - 65 + y) 26) + 65)
+
+decodeWithKey :: [Int] -> String -> String
+decodeWithKey _      []       = []
+decodeWithKey ys     (' ':xs) = ' ' : (decodeWithKey ys xs)
+decodeWithKey (y:ys) (x:xs)   = (decode (x, y)) : (decodeWithKey ys xs)
+
+vigenere :: String -> String
+vigenere = decodeWithKey (cycle [0, 11, 11, 24])
+
+caeser :: String -> String
+caeser = decodeWithKey (cycle [11])
+
+main :: IO ()
+main = do
+    putStrLn (vigenere "MEET AT DAWN")
+    putStrLn (caeser "MEET AT DAWN")
+    return ()