Data commit

Task/Vigen-re-cipher/Haskell/vigen-re-cipher.hs

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+import Data.Char
+import Text.Printf
+
+-- Perform encryption or decryption, depending on f.
+crypt f key = map toLetter . zipWith f (cycle key)
+  where toLetter = chr . (+) (ord 'A')
+
+-- Encrypt or decrypt one letter.
+enc k c = (ord k + ord c) `mod` 26
+dec k c = (ord c - ord k) `mod` 26
+
+-- Given a key, encrypt or decrypt an input string.
+encrypt = crypt enc
+decrypt = crypt dec
+
+-- Convert a string to have only upper case letters.
+convert = map toUpper . filter isLetter
+
+main :: IO ()
+main = do
+  let key  = "VIGENERECIPHER"
+      text = "Beware the Jabberwock, my son! The jaws that bite, "
+             ++ "the claws that catch!"
+      encr = encrypt key $ convert text
+      decr = decrypt key encr
+  printf "    Input: %s\n      Key: %s\nEncrypted: %s\nDecrypted: %s\n"
+    text key encr decr