2016 Update

Task/Caesar-cipher/Ela/caesar-cipher.ela

@@ -0,0 +1,28 @@
+open number char monad io string
+
+chars = "ABCDEFGHIJKLMOPQRSTUVWXYZ"
+
+caesar _ _ [] = ""
+caesar op key (x::xs) = check shifted ++ caesar op key xs
+  where orig = indexOf (string.upper $ toString x) chars
+        shifted = orig `op` key
+        check val | orig == -1 = x
+                  | val > 24 = trans $ val - 25
+                  | val < 0 = trans $ 25 + val
+                  | else = trans shifted
+        trans idx = chars:idx
+
+cypher = caesar (+)
+decypher = caesar (-)
+
+key = 2
+
+do
+  putStrLn "A string to encode:"
+  str <- readStr
+  putStr "Encoded string: "
+  cstr <- return <| cypher key str
+  put cstr
+  putStrLn ""
+  putStr "Decoded string: "
+  put $ decypher key cstr