haskell/step0_repl.hs

   1 import System.IO (hFlush, stdout)
   2
   3 import Readline (addHistory, readline, load_history)
   4
   5 type MalVal = String
   6
   7 -- read
   8
   9 mal_read :: String -> MalVal
  10 mal_read = id
  11
  12 -- eval
  13
  14 eval :: MalVal -> MalVal
  15 eval = id
  16
  17 -- print
  18
  19 mal_print :: MalVal -> String
  20 mal_print = id
  21
  22 -- repl
  23
  24 rep :: String -> String
  25 rep = mal_print . eval . mal_read
  26
  27 repl_loop :: IO ()
  28 repl_loop = do
  29     line <- readline "user> "
  30     case line of
  31         Nothing -> return ()
  32         Just "" -> repl_loop
  33         Just str -> do
  34             addHistory str
  35             putStrLn $ rep str
  36             hFlush stdout
  37             repl_loop
  38
  39 main :: IO ()
  40 main = do
  41     load_history
  42
  43     repl_loop