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module Minilang.IO where
import qualified Data.ByteString as BS
import qualified Data.Text as Text
import Data.Text.Encoding
( decodeUtf8With,
encodeUtf8,
)
import Data.Text.Encoding.Error (lenientDecode)
import Minilang.Lambda.Eval (eval)
import System.IO (Handle)
import Minilang.Lambda.Parser (parse, desugar)
-- | Read a "program" from @hin@ handle, evaluate it and dump the result
-- on @hout@.
runEval :: Handle -> Handle -> IO ()
runEval hin hout = do
programText <- decodeUtf8With lenientDecode <$> BS.hGetContents hin
let parsed = parse programText
result = case parsed of
Left err -> show err
Right ast ->
let term = desugar ast
env = mempty
in show $ eval term env
BS.hPut
hout
(encodeUtf8 (Text.pack result <> "\n"))
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