tvl-depot/scratch/haskell-programming-from-first-principles/io.hs
William Carroll a2475d2337 Partially complete IO chapter exercises
Inconveniently, I do not have the cipher code that I wrote from a previous
chapter, and I'm not eager to reimplement it.

TODO
- Implement encrypt
- Implement decrypt
- Read all characters from STDIN
2020-07-17 23:41:03 +01:00

35 lines
846 B
Haskell

module IOScratch where
import qualified System.Environment as SE
import qualified System.IO as SIO
--------------------------------------------------------------------------------
docs :: String
docs = "Pass -e to encrypt and -d to decrypt."
encryptStdin :: IO ()
encryptStdin = do
char <- SIO.hGetChar SIO.stdin
-- encrypt char
SIO.hPutStr SIO.stdout [char]
decryptStdin :: IO ()
decryptStdin = do
char <- SIO.hGetChar SIO.stdin
-- decrypt char
SIO.hPutStr SIO.stdout [char]
main :: IO ()
main = do
args <- SE.getArgs
case args of
[] ->
putStrLn $ "You did not pass enough arguments. " ++ docs
["-e"] ->
encryptStdin
["-d"] ->
decryptStdin
[x] ->
putStrLn $ "You passed an unsupported option: " ++ x ++ ". " ++ docs
_ ->
putStrLn $ "You passed too many arguments. " ++ docs