-- https://cryptii.com/pipes/caesar-cipher import Data.Char cipher :: [Char] -> Int -> [Char] cipher [] _ = [] cipher (x:xs) n = (if x `elem` chars then (chars !! (rem (n + (ind x)) nchars)) else x) : (cipher xs n) where ind x = (ord x) - 97 chars = ['a'..'z'] nchars = length chars -- Prelude> cipher "hello" 13 -- "uryyb" main = putStrLn $ cipher "hello" 13