wip: port REPL from minilang

1 files changed, 31 insertions, 0 deletions

diff --git a/lambda-calcul/haskell/src/Minilang/REPL/Purer.hs b/lambda-calcul/haskell/src/Minilang/REPL/Purer.hs
new file mode 100644
index 0000000..9e4bd22
--- /dev/null
+++ b/lambda-calcul/haskell/src/Minilang/REPL/Purer.hs
@@ -0,0 +1,31 @@
+{-# LANGUAGE GeneralizedNewtypeDeriving #-}
+module Minilang.REPL.Purer where
+
+
+import           Control.Monad.Catch
+import           Control.Monad.Catch.Pure (CatchT (..))
+import           Control.Monad.State
+import           Minilang.REPL.Types
+
+
+data PurerEnv = PurerEnv
+    { inputs    :: [In]
+    , outputs   :: [Out]
+    , purerREPL :: REPLEnv
+    }
+
+newtype PurerREPL a = PurerREPL { runPurer :: CatchT (State PurerEnv) a }
+  deriving (Functor, Applicative, Monad, MonadState PurerEnv, MonadCatch, MonadThrow)
+
+instance MonadREPL PurerREPL where
+  input = do
+    ins <- inputs <$> get
+    case ins of
+      []     -> pure EOF
+      (t:ts) -> modify (\ e -> e { inputs = ts }) >> pure t
+
+  output t  = modify $ \ e -> e { outputs = t : outputs e }
+  prompt    = pure ()
+  getEnv    = get >>= pure . purerREPL
+  setEnv e' = modify $ \ e -> e { purerREPL = e' }
+  load f    = pure $ Left $ REPLError $ "cannot load file " <> f <> " in Pure interpreter"