diff --git a/cubical.cabal b/cubical.cabal
index 701fc3d..05e2d0b 100644
--- a/cubical.cabal
+++ b/cubical.cabal
@@ -25,8 +25,11 @@ executable cubical
                      , containers ^>= 0.6
                      , bytestring ^>= 0.10
 
-                     , prettyprinter ^>= 1.7
+                     , prettyprinter               ^>= 1.7
                      , prettyprinter-ansi-terminal ^>= 1.1
+                     
+                     , haskeline            ^>= 0.8
+                     , optparse-applicative ^>= 0.15
 
   other-modules:       Presyntax.Lexer
                      , Presyntax.Parser
@@ -39,6 +42,7 @@ executable cubical
                      , Elab
                      , Elab.Eval
                      , Elab.Monad
+                     , Elab.WiredIn
 
   build-tool-depends:  alex:alex >= 3.2.4 && < 4.0
                     ,  happy:happy >= 1.19.12 && < 2.0
diff --git a/src/Elab.hs b/src/Elab.hs
index b4449c7..d35e720 100644
--- a/src/Elab.hs
+++ b/src/Elab.hs
@@ -1,5 +1,6 @@
 {-# LANGUAGE TupleSections, OverloadedStrings #-}
 {-# LANGUAGE DeriveAnyClass #-}
+{-# LANGUAGE ScopedTypeVariables #-}
 module Elab where
 
 import Control.Monad.Reader
@@ -8,29 +9,22 @@ import Control.Exception
 import qualified Data.Map.Strict as Map
 import Data.Typeable
 
+import Elab.WiredIn
 import Elab.Monad
 import Elab.Eval
 
 import qualified Presyntax.Presyntax as P
 
 import Syntax
+import Prettyprinter
 
 infer :: P.Expr -> ElabM (Term, NFType)
-infer (P.Span ex a b) = do
-  env <- ask
-  liftIO $
-      runElab (infer ex) env
-    `catches` [ Handler $ \e@WhileChecking{} -> throwIO e
-              , Handler $ \e -> throwIO (WhileChecking a b e)
-              ]
+infer (P.Span ex a b) = withSpan a b $ infer ex
 
 infer (P.Var t) = do
   name <- getNameFor t
-  case name of
-    Builtin _ wi -> elabWiredIn wi name
-    _ -> do
-      nft <- getNfType name
-      pure (Ref name, nft)
+  nft <- getNfType name
+  pure (Ref name, nft)
 
 infer (P.App p f x) = do
   (f, f_ty) <- infer f
@@ -39,20 +33,6 @@ infer (P.App p f x) = do
   x_nf <- eval x
   pure (App p (w f) x, r x_nf)
 
-infer (P.Pi p s d r) = do
-  d <- check d VType
-  d_nf <- eval d
-  assume (Bound s) d_nf $ do
-    r <- check r VType
-    pure (Pi p s d r, VType)
-
-infer (P.Sigma s d r) = do
-  d <- check d VType
-  d_nf <- eval d
-  assume (Bound s) d_nf $ do
-    r <- check r VType
-    pure (Sigma s d r, VType)
-
 infer (P.Proj1 x) = do
   (tm, ty) <- infer x
   (d, _, wp) <- isSigmaType ty
@@ -70,13 +50,7 @@ infer exp = do
   pure (tm, t)
 
 check :: P.Expr -> NFType -> ElabM Term
-check (P.Span ex a b) ty = do
-  env <- ask
-  liftIO $
-      runElab (check ex ty) env
-    `catches` [ Handler $ \e@WhileChecking{} -> throwIO e
-              , Handler $ \e -> throwIO (WhileChecking a b e)
-              ]
+check (P.Span ex a b) ty = withSpan a b $ check ex ty
 
 check (P.Lam p var body) (VPi p' dom (Closure _ rng)) | p == p' =
   assume (Bound var) dom $
@@ -98,13 +72,32 @@ check (P.Pair a b) ty = do
   b <- check b (r a_nf)
   pure (wp (Pair a b))
 
+check (P.Pi p s d r) ty = do
+  isSort ty
+  d <- check d ty
+  d_nf <- eval d
+  assume (Bound s) d_nf $ do
+    r <- check r ty
+    pure (Pi p s d r)
+
+check (P.Sigma s d r) ty = do
+  isSort ty
+  d <- check d ty
+  d_nf <- eval d
+  assume (Bound s) d_nf $ do
+    r <- check r ty
+    pure (Sigma s d r)
+
 check exp ty = do
   (tm, has) <- switch $ infer exp
-  unify has ty
-  pure tm
+  wp <- isConvertibleTo has ty
+  pure (wp tm)
 
-elabWiredIn :: WiredIn -> Name -> ElabM (Term, NFType)
-elabWiredIn WiType _ = pure (Type, VType)
+isSort :: NFType -> ElabM ()
+isSort VType                = pure ()
+isSort VTypeω               = pure ()
+isSort vt@(VNe HMeta{} _)   = unify vt VType
+isSort vt = liftIO . throwIO $ NotEqual vt VType
 
 isPiType :: P.Plicity -> NFType -> ElabM (Value, NFType -> NFType, Term -> Term)
 isPiType p (VPi p' d (Closure _ k)) | p == p' = pure (d, k, id)
@@ -130,10 +123,12 @@ identityTy :: NFType
 identityTy = VPi P.Im VType (Closure "A" $ \t -> VPi P.Ex t (Closure "_" (const t)))
 
 checkStatement :: P.Statement -> ElabM a -> ElabM a
+checkStatement (P.SpanSt s a b) k = withSpan a b $ checkStatement s k
+
 checkStatement (P.Decl name ty) k = do
-  ty <- check ty VType
+  ty <- check ty VTypeω
   ty_nf <- eval ty
-  assume (Defined name) ty_nf k
+  assumes (Defined <$> name) ty_nf k
 
 checkStatement (P.Defn name rhs) k = do
   ty <- asks (Map.lookup (Defined name) . getEnv)
@@ -150,12 +145,42 @@ checkStatement (P.Defn name rhs) k = do
       rhs_nf <- eval rhs
       define (Defined name) ty_nf rhs_nf k
 
-checkProgram :: [P.Statement] -> ElabM ElabEnv
-checkProgram [] = ask
-checkProgram (st:sts) = checkStatement st $ checkProgram sts
+checkStatement (P.Builtin winame var) k = do
+  wi <-
+    case Map.lookup winame wiredInNames of
+      Just wi -> pure wi
+      _ -> liftIO . throwIO $ NoSuchPrimitive winame
 
-newtype Redefinition = Redefinition { getRedefName :: Name }
-  deriving (Show, Typeable, Exception)
+  let
+    check = do
+      nm <- getNameFor var
+      ty <- getNfType nm
+      unify ty (wiType wi)
+        `withNote` hsep [ "Previous definition of", pretty nm, "here" ]
+        `seeAlso` nm
 
-data WhileChecking = WhileChecking { startPos :: P.Posn, endPos :: P.Posn, exc :: SomeException }
+  env <- ask
+  liftIO $
+    runElab check env `catch` \(_ :: NotInScope) -> pure ()
+
+  define (Defined var) (wiType wi) (wiValue wi) k
+
+checkStatement (P.ReplNf e) k = do
+  (e, _) <- infer e
+  e_nf <- eval e
+  h <- asks commHook
+  liftIO (h e_nf)
+  k
+
+checkStatement (P.ReplTy e) k = do
+  (_, ty) <- infer e
+  h <- asks commHook
+  liftIO (h ty)
+  k
+
+checkProgram :: [P.Statement] -> ElabM a -> ElabM a
+checkProgram [] k = k
+checkProgram (st:sts) k = checkStatement st $ checkProgram sts k
+
+newtype Redefinition = Redefinition { getRedefName :: Name }
   deriving (Show, Typeable, Exception)
\ No newline at end of file
diff --git a/src/Elab/Eval.hs b/src/Elab/Eval.hs
index 2ca0df1..7ef35b9 100644
--- a/src/Elab/Eval.hs
+++ b/src/Elab/Eval.hs
@@ -1,5 +1,6 @@
 {-# LANGUAGE LambdaCase #-}
 {-# LANGUAGE DeriveAnyClass #-}
+{-# LANGUAGE ScopedTypeVariables #-}
 module Elab.Eval where
 
 import Control.Monad.Reader
@@ -15,6 +16,7 @@ import Data.Foldable
 import Data.IORef
 import Data.Maybe
 
+import {-# SOURCE #-} Elab.WiredIn
 import Elab.Monad
 
 import Presyntax.Presyntax (Plicity(..))
@@ -22,6 +24,7 @@ import Presyntax.Presyntax (Plicity(..))
 import Syntax
 
 import System.IO.Unsafe
+import Syntax.Pretty
 
 eval :: Term -> ElabM Value
 eval t = asks (flip evalWithEnv t)
@@ -61,7 +64,18 @@ zonkIO (VLam p (Closure s k)) = pure $ VLam p (Closure s (zonk . k))
 zonkIO (VPi p d (Closure s k)) = VPi p <$> zonkIO d <*> pure (Closure s (zonk . k))
 zonkIO (VSigma d (Closure s k)) = VSigma <$> zonkIO d <*> pure (Closure s (zonk . k))
 zonkIO (VPair a b) = VPair <$> zonkIO a <*> zonkIO b
+
+-- Sorts
 zonkIO VType = pure VType
+zonkIO VTypeω = pure VTypeω
+
+zonkIO VI = pure VI
+zonkIO VI0 = pure VI0
+zonkIO VI1 = pure VI1
+
+zonkIO (VIAnd x y) = iand <$> zonkIO x <*> zonkIO y
+zonkIO (VIOr x y) = ior <$> zonkIO x <*> zonkIO y
+zonkIO (VINot x) = inot <$> zonkIO x
 
 zonk :: Value -> Value
 zonk = unsafePerformIO . zonkIO
@@ -93,6 +107,14 @@ evalWithEnv e (Proj1 a) = vProj1 (evalWithEnv e a)
 evalWithEnv e (Proj2 a) = vProj2 (evalWithEnv e a)
 
 evalWithEnv _ Type = VType
+evalWithEnv _ Typeω = VTypeω
+evalWithEnv _ I = VI
+evalWithEnv _ I0 = VI0
+evalWithEnv _ I1 = VI1
+
+evalWithEnv e (IAnd x y) = iand (evalWithEnv e x) (evalWithEnv e y)
+evalWithEnv e (IOr x y) = ior (evalWithEnv e x) (evalWithEnv e y)
+evalWithEnv e (INot x) = inot (evalWithEnv e x)
 
 vApp :: Plicity -> Value -> Value -> Value
 vApp p (VLam p' k) arg = assert (p == p') $ clCont k arg
@@ -112,58 +134,67 @@ vProj2 x = error $ "can't proj2 " ++ show x
 data NotEqual = NotEqual Value Value
   deriving (Show, Typeable, Exception)
 
-unify :: Value -> Value -> ElabM ()
-unify topa topb = join $ go <$> forceIO topa <*> forceIO topb where
+unify' :: Value -> Value -> ElabM ()
+unify' topa topb = join $ go <$> forceIO topa <*> forceIO topb where
   go (VNe (HMeta mv) sp) rhs = solveMeta mv sp rhs
   go rhs (VNe (HMeta mv) sp) = solveMeta mv sp rhs
 
   go (VNe x a) (VNe x' a')
     | x == x', length a == length a' =
-      traverse_ (uncurry unifySpine) (zip a a')
+      traverse_ (uncurry unify'Spine) (zip a a')
     | otherwise = fail
 
   go (VLam p (Closure _ k)) vl = do
     t <- VVar . Bound <$> newName
-    unify (k t) (vApp p vl t)
+    unify' (k t) (vApp p vl t)
 
   go vl (VLam p (Closure _ k)) = do
     t <- VVar . Bound <$> newName
-    unify (vApp p vl t) (k t)
+    unify' (vApp p vl t) (k t)
 
-  go (VPair a b) vl = unify a (vProj1 vl) *> unify b (vProj2 vl)
-  go vl (VPair a b) = unify (vProj1 vl) a *> unify (vProj2 vl) b
+  go (VPair a b) vl = unify' a (vProj1 vl) *> unify' b (vProj2 vl)
+  go vl (VPair a b) = unify' (vProj1 vl) a *> unify' (vProj2 vl) b
 
   go (VPi p d (Closure _ k)) (VPi p' d' (Closure _ k')) | p == p' = do
     t <- VVar . Bound <$> newName
-    unify d d'
-    unify (k t) (k' t)
+    unify' d d'
+    unify' (k t) (k' t)
 
   go (VSigma d (Closure _ k)) (VSigma d' (Closure _ k')) = do
     t <- VVar . Bound <$> newName
-    unify d d'
-    unify (k t) (k' t)
+    unify' d d'
+    unify' (k t) (k' t)
 
-  go VType VType = pure ()
+  go VType VType   = pure ()
+  go VTypeω VTypeω = pure ()
+
+  go VI VI   = pure ()
+  go VI0 VI0 = pure ()
+  go VI1 VI1 = pure ()
 
   go _ _ = fail
 
   fail = liftIO . throwIO $ NotEqual topa topb
 
-  unifySpine (PApp a v) (PApp a' v')
-    | a == a' = unify v v'
+  unify'Spine (PApp a v) (PApp a' v')
+    | a == a' = unify' v v'
+
+  unify'Spine PProj1 PProj1 = pure ()
+  unify'Spine PProj2 PProj2 = pure ()
 
-  unifySpine PProj1 PProj1 = pure ()
-  unifySpine PProj2 PProj2 = pure ()
+  unify'Spine _ _ = fail
 
-  unifySpine _ _ = fail
+unify :: Value -> Value -> ElabM ()
+unify a b = unify' a b `catchElab` \(_ :: SomeException) -> liftIO $ throwIO (NotEqual a b)
 
 isConvertibleTo :: Value -> Value -> ElabM (Term -> Term)
 VPi Im d (Closure _v k) `isConvertibleTo` ty = do
   meta <- newMeta d
   cont <- k meta `isConvertibleTo` ty
   pure (\f -> cont (App Ex f (quote meta)))
+VType `isConvertibleTo` VTypeω = pure id
 isConvertibleTo a b = do
-  unify a b
+  unify' a b
   pure id
 
 newMeta :: Value -> ElabM Value
@@ -193,7 +224,7 @@ _nameCounter = unsafePerformIO $ newIORef 0
 solveMeta :: MV -> [Projection] -> Value -> ElabM ()
 solveMeta m@(MV _ cell) sp rhs = do
   env <- ask
-  liftIO $ print (m, sp, rhs)
+  liftIO $ putStrLn (showValue (VNe (HMeta m) sp) ++ " ≡? " ++ showValue rhs)
   names <- checkSpine Set.empty sp
   checkScope (Set.fromList (Bound <$> names)) rhs
   let tm = quote rhs
@@ -231,6 +262,15 @@ checkScope scope (VSigma d (Closure n k)) = do
 checkScope s (VPair a b) = traverse_ (checkScope s) [a, b]
 
 checkScope _ VType = pure ()
+checkScope _ VTypeω = pure ()
+
+checkScope _ VI = pure ()
+checkScope _ VI0 = pure ()
+checkScope _ VI1 = pure ()
+
+checkScope s (VIAnd x y) = traverse_ (checkScope s) [x, y]
+checkScope s (VIOr x y)  = traverse_ (checkScope s) [x, y]
+checkScope s (VINot x)   = checkScope s x
 
 checkSpine :: Set Name -> [Projection] -> ElabM [T.Text]
 checkSpine scope (PApp Ex (VVar n@(Bound t)):xs)
diff --git a/src/Elab/Monad.hs b/src/Elab/Monad.hs
index f8848e0..cf48727 100644
--- a/src/Elab/Monad.hs
+++ b/src/Elab/Monad.hs
@@ -7,35 +7,52 @@ module Elab.Monad where
 import Control.Monad.Reader
 import Control.Exception
 
+import Data.Text.Prettyprint.Doc.Render.Terminal (AnsiStyle)
 import qualified Data.Map.Strict as Map
+import Data.Text.Prettyprint.Doc
 import Data.Map.Strict (Map)
 import Data.Text (Text)
 import Data.Typeable
 
 import Syntax
-import qualified Data.Text as T
+import qualified Presyntax.Presyntax as P
 
-data ElabEnv = ElabEnv { getEnv :: Map Name (NFType, Value), nameMap :: Map Text Name, pingPong :: Int }
+data ElabEnv =
+  ElabEnv { getEnv      :: Map Name (NFType, Value)
+
+          , nameMap     :: Map Text Name
+          , pingPong    :: Int
+          , commHook    :: Value -> IO ()
+
+          , currentSpan :: Maybe (P.Posn, P.Posn)
+          , whereBound  :: Map Name (P.Posn, P.Posn)
+          }
 
 newtype ElabM a = ElabM { runElab :: ElabEnv -> IO a }
   deriving (Functor, Applicative, Monad, MonadReader ElabEnv, MonadIO)
     via ReaderT ElabEnv IO
 
-newtype NotInScope = NotInScope { nameNotInScope :: Name }
-  deriving          (Show, Typeable)
-  deriving anyclass (Exception)
-
 emptyEnv :: ElabEnv
-emptyEnv = ElabEnv mempty (Map.singleton (T.pack "Type") (Builtin (T.pack "Type") WiType)) 0
+emptyEnv = ElabEnv mempty mempty 0 (const (pure ())) Nothing mempty
 
 assume :: Name -> Value -> ElabM a -> ElabM a
 assume nm ty = local go where
-  go x = x { getEnv = Map.insert nm (ty, VVar nm) (getEnv x), nameMap = Map.insert (getNameText nm) nm (nameMap x) }
+  go x = x { getEnv = Map.insert nm (ty, VVar nm) (getEnv x)
+           , nameMap = Map.insert (getNameText nm) nm (nameMap x)
+           , whereBound = maybe (whereBound x) (flip (Map.insert nm) (whereBound x)) (currentSpan x)
+           }
+
+assumes :: [Name] -> Value -> ElabM a -> ElabM a
+assumes nm ty = local go where
+  go x = x { getEnv = Map.union (Map.fromList (map (\v -> (v, (ty, VVar v))) nm)) (getEnv x)
+           , nameMap = Map.union (Map.fromList (map ((,) <$> getNameText <*> id) nm)) (nameMap x)
+           , whereBound = maybe (whereBound x) (\l -> Map.union (Map.fromList (zip nm (repeat l))) (whereBound x)) (currentSpan x)
+           }
+
 
 getNameText :: Name -> Text
 getNameText (Bound x) = x
 getNameText (Defined x) = x
-getNameText (Builtin x _) = x
 
 define :: Name -> Value -> Value -> ElabM a -> ElabM a
 define nm ty vl = local go where
@@ -68,4 +85,48 @@ switch k =
     depth <- asks pingPong
     when (depth >= 128) $ liftIO $ throwIO StackOverflow
     local go k
-  where go e = e { pingPong = pingPong e + 1 }
\ No newline at end of file
+  where go e = e { pingPong = pingPong e + 1 }
+
+newtype NotInScope = NotInScope { nameNotInScope :: Name }
+  deriving          (Show, Typeable)
+  deriving anyclass (Exception)
+
+data AttachedNote = AttachedNote { getNote :: Doc AnsiStyle, getExc :: SomeException }
+  deriving          (Show, Typeable)
+  deriving anyclass (Exception)
+
+withNote :: ElabM a -> Doc AnsiStyle -> ElabM a
+withNote k note = do
+  env <- ask
+  liftIO $
+      runElab k env
+    `catch` \e -> throwIO (AttachedNote note e)
+
+data WhileChecking = WhileChecking { startPos :: P.Posn, endPos :: P.Posn, exc :: SomeException }
+  deriving (Show, Typeable, Exception)
+
+withSpan :: P.Posn -> P.Posn -> ElabM a -> ElabM a
+withSpan a b k = do
+  env <- ask
+  liftIO $
+      runElab k env{ currentSpan = Just (a, b) }
+    `catches` [ Handler $ \e@WhileChecking{} -> throwIO e
+              , Handler $ \e -> throwIO (WhileChecking a b e)
+              ]
+
+data SeeAlso = SeeAlso { saStartPos :: P.Posn, saEndPos :: P.Posn, saExc :: SomeException }
+  deriving (Show, Typeable, Exception)
+
+seeAlso :: ElabM a -> Name -> ElabM a
+seeAlso k nm = do
+  env <- ask
+  case Map.lookup nm (whereBound env) of
+    Just l ->
+      liftIO $ runElab k env
+        `catch` \e -> throwIO (SeeAlso (fst l) (snd l) e)
+    Nothing -> k
+
+catchElab :: Exception e => ElabM a -> (e -> ElabM a) -> ElabM a
+catchElab k h = do
+  env <- ask
+  liftIO $ runElab k env `catch` \e -> runElab (h e) env
\ No newline at end of file
diff --git a/src/Elab/WiredIn.hs b/src/Elab/WiredIn.hs
new file mode 100644
index 0000000..19b1c0a
--- /dev/null
+++ b/src/Elab/WiredIn.hs
@@ -0,0 +1,93 @@
+{-# LANGUAGE BlockArguments #-}
+{-# LANGUAGE LambdaCase #-}
+{-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE DerivingStrategies #-}
+{-# LANGUAGE DeriveAnyClass #-}
+module Elab.WiredIn where
+
+import Syntax
+import Data.Map.Strict (Map)
+import Data.Text (Text)
+import qualified Data.Map.Strict as Map
+import Control.Exception
+import Data.Typeable
+import qualified Presyntax.Presyntax as P
+import Elab.Eval
+
+wiType :: WiredIn -> NFType
+wiType WiType     = VType
+wiType WiPretype  = VTypeω
+
+wiType WiInterval = VTypeω
+wiType WiI0       = VI
+wiType WiI1       = VI
+
+wiType WiIAnd      = VI ~> VI ~> VI
+wiType WiIOr       = VI ~> VI ~> VI
+wiType WiINot      = VI ~> VI
+
+wiValue :: WiredIn -> Value
+wiValue WiType     = VType
+wiValue WiPretype  = VTypeω
+
+wiValue WiInterval = VI
+wiValue WiI0       = VI0
+wiValue WiI1       = VI1
+
+wiValue WiIAnd      = fun \x -> fun \y -> iand x y
+wiValue WiIOr       = fun \x -> fun \y -> ior x y
+wiValue WiINot      = fun inot
+
+(~>) :: Value -> Value -> Value
+a ~> b = VPi P.Ex a (Closure "_" (const b))
+infixr 7 ~>
+
+fun :: (Value -> Value) -> Value
+fun k = VLam P.Ex $ Closure "x" (k . force)
+
+dprod :: Value -> (Value -> Value) -> Value
+dprod a b = VPi P.Ex a (Closure "x" b)
+
+wiredInNames :: Map Text WiredIn
+wiredInNames = Map.fromList
+  [ ("pretype", WiPretype)
+  , ("type", WiType)
+  , ("interval", WiInterval)
+  , ("i0", WiI0)
+  , ("i1", WiI1)
+  , ("iand", WiIAnd)
+  , ("ior",  WiIOr)
+  , ("inot", WiINot)
+  ]
+
+newtype NoSuchPrimitive = NoSuchPrimitive { getUnknownPrim :: Text }
+  deriving (Show, Typeable)
+  deriving anyclass (Exception)
+
+-- Interval operations
+
+iand, ior :: Value -> Value -> Value
+iand = \case
+  VI1 -> id
+  VI0 -> const VI0
+  x -> \case
+    VI0 -> VI0
+    VI1 -> x
+    y -> VIAnd x y
+
+ior = \case
+  VI0 -> id
+  VI1 -> const VI1
+  x -> \case
+    VI1 -> VI1
+    VI0 -> x
+    y -> VIOr x y
+
+inot :: Value -> Value
+inot = \case
+  VI0 -> VI1
+  VI1 -> VI0
+  VIOr x y -> VIAnd (inot x) (inot y)
+  VIAnd x y -> VIOr (inot x) (inot y)
+  VINot x -> x
+  x -> VINot x
\ No newline at end of file
diff --git a/src/Elab/WiredIn.hs-boot b/src/Elab/WiredIn.hs-boot
new file mode 100644
index 0000000..caaf086
--- /dev/null
+++ b/src/Elab/WiredIn.hs-boot
@@ -0,0 +1,9 @@
+module Elab.WiredIn where
+
+import Syntax
+
+wiType  :: WiredIn -> NFType
+wiValue :: WiredIn -> NFType
+
+iand, ior :: Value -> Value -> Value
+inot :: Value -> Value
\ No newline at end of file
diff --git a/src/Main.hs b/src/Main.hs
index dd2b5ec..643f15b 100644
--- a/src/Main.hs
+++ b/src/Main.hs
@@ -13,24 +13,92 @@ import qualified Data.Text as T
 import Data.Text ( Text )
 import Data.Foldable
 
-import Elab.Monad
+import Elab.Monad hiding (switch)
 import Elab.Eval
 import Elab
 
 import Presyntax.Presyntax (Posn(Posn))
 import Presyntax.Parser
-import Presyntax.Tokens
 import Presyntax.Lexer
 
 import System.Exit
 import Syntax.Pretty
+import Elab.WiredIn
+import Options.Applicative
+import Control.Monad
+import Syntax
+import Prettyprinter
+import Control.Monad.IO.Class
+import Control.Monad.Reader
+import System.Console.Haskeline
 
 main :: IO ()
 main = do
-  t <- Bsl.readFile "test.tt"
-  let Right tks = runAlex t parseProg
-  env <- runElab (checkProgram tks) emptyEnv `catch` \e -> displayAndDie (T.decodeUtf8 (Bsl.toStrict t)) (e :: SomeException)
-  for_ (Map.toList (getEnv env)) $ \(n, x) -> putStrLn $ show n ++ " : " ++ showValue (zonk (fst x))
+  opts <- execParser parser
+  case opts of
+    Load files -> do
+      env <- checkFiles files
+      enterReplIn env
+    Check files verbose -> do
+      env <- checkFiles files
+      when verbose $ dumpEnv (getEnv env)
+    Repl -> enterReplIn emptyEnv
+
+enterReplIn :: ElabEnv -> IO ()
+enterReplIn env = runInputT defaultSettings (loop env') where
+  env' = env { commHook = T.putStrLn . render . prettyTm . quote }
+
+  loop :: ElabEnv -> InputT IO ()
+  loop env = do
+    inp <- fmap T.pack <$> getInputLine "% "
+    case inp of
+      Nothing -> pure ()
+      Just inp ->
+        case runAlex (Bsl.fromStrict (T.encodeUtf8 inp)) parseRepl of
+          Left e -> do
+            liftIO $ print e
+            loop env
+          Right st -> do
+            env <- liftIO $
+              runElab (checkStatement st ask) env
+                `catch` \e -> do
+                  displayExceptions' inp (e :: SomeException)
+                  pure env
+            loop env
+
+checkFiles :: [String] -> IO ElabEnv
+checkFiles files = runElab (go files ask) emptyEnv where
+  go [] k = k
+  go (x:xs) k = do
+    code <- liftIO $ Bsl.readFile x
+    case runAlex code parseProg of
+      Left e -> liftIO $ print e *> error (show e)
+      Right prog -> do
+        env <- ask
+        liftIO $ runElab (checkProgram prog (go xs k)) env
+                  `catch` \e -> displayAndDie (T.decodeUtf8 (Bsl.toStrict code)) (e :: SomeException)
+
+dumpEnv :: Map.Map Name (NFType, Value) -> IO ()
+dumpEnv env = for_ (Map.toList env) $ \(name, (nft, _)) ->
+  T.putStrLn $ render (pretty name <+> colon <+> prettyTm (quote (zonk nft)))
+
+parser :: ParserInfo Opts
+parser = info (subparser (load <> check) <|> pure Repl <**> helper) (header "cubical - a cubical programming language")
+  where
+    load  = command "load" $ info (fmap Load (some (argument str (metavar "file..."))) <**> helper) (progDesc "Check and load a list of files in the REPL")
+    check = command "check" $
+      info ((Check <$> some (argument str (metavar "file..."))
+                  <*> switch ( long "verbose"
+                            <> short 'v'
+                            <> help "Print the types of all declared/defined values"))
+       <**> helper)
+           (progDesc "Check a list of files")
+
+data Opts
+  = Load  { files :: [String] }
+  | Check { files :: [String], verbose :: Bool }
+  | Repl
+  deriving (Eq, Show, Ord)
 
 displayAndDie :: Exception e => Text -> e -> IO a
 displayAndDie lines e = do
@@ -42,12 +110,22 @@ displayExceptions lines =
   [ Handler \(WhileChecking a b e) -> do
       T.putStrLn $ squiggleUnder a b lines
       displayExceptions' lines e
+  , Handler \(SeeAlso a b e) -> do
+      displayExceptions' lines e
+      T.putStrLn $ squiggleUnder a b lines
   , Handler \(NotEqual ta tb) -> do
       putStrLn . unlines $
         [ "\x1b[1;31merror\x1b[0m: Mismatch between actual and expected types:"
         , "  * \x1b[1mActual\x1b[0m:   " ++ showValue (zonk ta)
         , "  * \x1b[1mExpected\x1b[0m: " ++ showValue (zonk tb)
         ]
+  , Handler \(NoSuchPrimitive x) -> do
+      putStrLn $ "Unknown primitive: " ++ T.unpack x
+  , Handler \(NotInScope x) -> do
+      putStrLn $ "Variable not in scope: " ++ show x
+  , Handler \(AttachedNote n e) -> do
+      displayExceptions' lines e
+      T.putStrLn $ "\x1b[1;32mnote\x1b[0m: " <> render n
   ]
 
 displayExceptions' :: Exception e => Text -> e -> IO ()
diff --git a/src/Presyntax/Lexer.x b/src/Presyntax/Lexer.x
index a5475c0..a5e116b 100644
--- a/src/Presyntax/Lexer.x
+++ b/src/Presyntax/Lexer.x
@@ -16,9 +16,9 @@ $white_nol = $white # \n
 tokens :-
   $white_nol+                   ;
   
--- zero state: normal lexing
-<0> $alpha [$alpha $digit \_ \']* { yield TokVar }
+<0,prtext> $alpha [$alpha $digit \_ \']* { yield TokVar }
 
+-- zero state: normal lexing
 <0> \=                            { always TokEqual }
 <0> \:                            { always TokColon }
 <0> \,                            { always TokComma }
@@ -37,7 +37,14 @@ tokens :-
 <0> \}                            { always TokCBrace }
 <0> \;                            { always TokSemi }
 
-<0>       \n                      { just $ pushStartCode newline }
+<0> \n                            { just $ pushStartCode newline }
+
+<0> "{-#"                         { \i l -> pushStartCode prkw *> always TokOPragma i l }
+<prkw> "PRIMITIVE"                { \i l -> popStartCode *> pushStartCode prtext *> always TokPrim i l }
+<prtext> "#-}"                    { \i l -> popStartCode *> always TokCPragma i l }
+
+<0> ":let"                        { always TokReplLet }
+<0> ":t"("y"|"yp"|"ype"|())       { yield TokReplT }
 
 -- newline: emit a semicolon when de-denting
 <newline> {
@@ -45,7 +52,6 @@ tokens :-
   () { offsideRule }
 }
 
-
 {
 alexEOF :: Alex Token
 alexEOF = do
@@ -53,6 +59,8 @@ alexEOF = do
   pure $ Token TokEof l c
 
 yield k (AlexPn _ l c, _, s, _) i = pure (Token (k $! (T.decodeUtf8 (Lbs.toStrict (Lbs.take i s)))) l c)
+
+always :: TokenClass -> AlexInput -> Int64 -> Alex Token
 always k x i = yield (const k) x i
 
 data AlexUserState = AlexUserState { layoutColumns :: [Int], startCodes :: [Int] }
@@ -83,7 +91,7 @@ popStartCode = do
       alexSetStartCode x
 
 offsideRule :: AlexInput -> Int64 -> Alex Token
-offsideRule i@(AlexPn p line col, _, s, _) l = do
+offsideRule (AlexPn _ line col, _, _, _) _ = do
   ~(col':_) <- layoutColumns <$> getUserState
   case col `compare` col' of
     EQ -> do
diff --git a/src/Presyntax/Parser.y b/src/Presyntax/Parser.y
index 75d4ed3..ff6e9ad 100644
--- a/src/Presyntax/Parser.y
+++ b/src/Presyntax/Parser.y
@@ -15,6 +15,7 @@ import Prelude hiding (span)
 %name parseExp  Exp
 %name parseStmt Statement
 %name parseProg Program
+%name parseRepl ReplStatement
 
 %tokentype { Token }
 
@@ -25,24 +26,32 @@ import Prelude hiding (span)
 %error { parseError }
 
 %token
-  var     { $$@(Token (TokVar _) _ _) }
-  '('     { Token TokOParen _ _ }
-  ')'     { Token TokCParen _ _ }
+  var         { Token (TokVar _) _ _ }
+  '('         { Token TokOParen _ _ }
+  ')'         { Token TokCParen _ _ }
 
-  '{'     { Token TokOBrace _ _ }
-  '}'     { Token TokCBrace _ _ }
+  '{'         { Token TokOBrace _ _ }
+  '}'         { Token TokCBrace _ _ }
 
-  '\\'    { Token TokLambda _ _ }
+  '{-#'       { Token TokOPragma _ _ }
+  '#-}'       { Token TokCPragma _ _ }
+
+  '\\'        { Token TokLambda _ _ }
   
-  '->'    { Token TokArrow _ _ }
-  ':'     { Token TokColon _ _ }
-  ';'     { Token TokSemi  _ _ }
-  '='     { Token TokEqual _ _ }
-  ','     { Token TokComma _ _ }
-  '*'     { Token TokStar _ _ }
+  '->'        { Token TokArrow _ _ }
+  ':'         { Token TokColon _ _ }
+  ';'         { Token TokSemi  _ _ }
+  '='         { Token TokEqual _ _ }
+  ','         { Token TokComma _ _ }
+  '*'         { Token TokStar _ _ }
+
+  '.1'        { Token TokPi1 _ _ }
+  '.2'        { Token TokPi2 _ _ }
 
-  '.1'     { Token TokPi1 _ _ }
-  '.2'     { Token TokPi2 _ _ }
+  'PRIMITIVE' { Token TokPrim _ _ }
+
+  ':let'      { Token TokReplLet _ _ }
+  ':t'        { Token (TokReplT _) _ _ }
 
 %%
 
@@ -52,18 +61,18 @@ Exp
   | Exp '{' Exp '}'                   { span $1 $4 $ App Im $1 $3 }
 
   | '\\' LambdaList '->' Exp          { span $1 $4 $ makeLams $2 $4 }
-  | '(' VarList ':' Exp ')' ProdTail  { span $1 $6 $ makePis Ex $2 $4 $6 }
-  | '{' VarList ':' Exp '}' ProdTail  { span $1 $6 $ makePis Im $2 $4 $6 }
+  | '(' VarList ':' Exp ')' ProdTail  { span $1 $6 $ makePis Ex (thd $2) $4 $6 }
+  | '{' VarList ':' Exp '}' ProdTail  { span $1 $6 $ makePis Im (thd $2) $4 $6 }
   | ExpProj '->' Exp                  { span $1 $3 $ Pi Ex (T.singleton '_') $1 $3 }
 
-  | '(' VarList ':' Exp ')' '*'  Exp  { span $1 $7 $ makeSigmas $2 $4 $7 }
+  | '(' VarList ':' Exp ')' '*'  Exp  { span $1 $7 $ makeSigmas (thd $2) $4 $7 }
   | ExpProj '*' Exp                   { span $1 $3 $ Sigma (T.singleton '_') $1 $3 }
 
   | ExpProj                           { $1 }
 
 ProdTail :: { Expr }
-  : '(' VarList ':' Exp ')' ProdTail  { span $1 $6 $ makePis Ex $2 $4 $6 }
-  | '{' VarList ':' Exp '}' ProdTail  { span $1 $6 $ makePis Im $2 $4 $6 }
+  : '(' VarList ':' Exp ')' ProdTail  { span $1 $6 $ makePis Ex (thd $2) $4 $6 }
+  | '{' VarList ':' Exp '}' ProdTail  { span $1 $6 $ makePis Im (thd $2) $4 $6 }
   | '->' Exp                          { span $2 $2 $ $2 }
 
 LambdaList :: { [(Plicity, Text)] }
@@ -77,9 +86,9 @@ LhsList :: { [(Plicity, Text)] }
   :            { [] }
   | LambdaList { $1 }
 
-VarList :: { [Text] }
-  : var         { [getVar $1] }
-  | var VarList { getVar $1:$2 }
+VarList :: { (Posn, Posn, [Text]) }
+  : var         { (startPosn $1, endPosn $1, [getVar $1]) }
+  | var VarList { case $2 of (_, end, xs) -> (startPosn $1, end, getVar $1:xs) }
 
 ExpProj :: { Expr }
   : ExpProj '.1' { span $1 $2 $ Proj1 $1 }
@@ -95,13 +104,25 @@ Tuple :: { Expr }
   | Exp ',' Tuple { span $1 $3 $ Pair $1 $3 }
 
 Statement :: { Statement }
-  : var ':' Exp         { Decl (getVar $1) $3 }
-  | var LhsList '=' Exp { Defn (getVar $1) (makeLams $2 $4) }
+  : VarList ':' Exp     { spanSt $1 $3 $ Decl (thd $1) $3 }
+  | var LhsList '=' Exp { spanSt $1 $4 $ Defn (getVar $1) (makeLams $2 $4) }
+  | '{-#' Pragma '#-}'  { spanSt $1 $3 $ $2 }
+
+ReplStatement :: { Statement }
+  : Exp                        { spanSt $1 $1 $ ReplNf $1 }
+  | ':t' Exp                   { spanSt $1 $2 $ ReplTy $2 }
+  | ':let' VarList ':' Exp     { spanSt $1 $4 $ Decl (thd $2) $4 }
+  | ':let' var LhsList '=' Exp { spanSt $1 $5 $ Defn (getVar $2) (makeLams $3 $5) }
+  | '{-#' Pragma '#-}'         { spanSt $1 $3 $ $2 }
 
 Program :: { [Statement] }
   : Statement             { [$1] }
   | Statement ';' Program { $1:$3 }
 
+Pragma :: { Statement }
+  : 'PRIMITIVE' var var { Builtin (getVar $2) (getVar $3) }
+  | 'PRIMITIVE' var     { Builtin (getVar $2) (getVar $2) }
+
 {
 lexer cont = alexMonadScan >>= cont
 
@@ -126,7 +147,16 @@ instance HasPosn Expr where
   endPosn (Span _ _ e) = e
   endPosn _            = error "no end posn in parsed expression?"
 
+instance HasPosn (Posn, Posn, a) where
+  startPosn (s, _, _) = s
+  endPosn   (_, e, _) = e
+
+thd :: (a, b, c) -> c
+thd (x, y, z) = z
+
+
 span s e ex = Span ex (startPosn s) (endPosn e)
+spanSt s e ex = SpanSt ex (startPosn s) (endPosn e)
 
 getVar (Token (TokVar s) _ _) = s
 getVar _ = error "getVar non-var"
diff --git a/src/Presyntax/Presyntax.hs b/src/Presyntax/Presyntax.hs
index a8a8632..2c33e9b 100644
--- a/src/Presyntax/Presyntax.hs
+++ b/src/Presyntax/Presyntax.hs
@@ -1,5 +1,6 @@
 module Presyntax.Presyntax where
 
+
 import Data.Text (Text)
 
 data Plicity
@@ -22,8 +23,14 @@ data Expr
   deriving (Eq, Show, Ord)
 
 data Statement
-  = Decl Text Expr
-  | Defn Text Expr
+  = Decl    [Text] Expr
+  | Defn    Text Expr
+  | Builtin Text Text
+
+  | ReplNf Expr -- REPL eval
+  | ReplTy Expr -- REPL :t
+
+  | SpanSt Statement Posn Posn
   deriving (Eq, Show, Ord)
 
 data Posn
diff --git a/src/Presyntax/Tokens.hs b/src/Presyntax/Tokens.hs
index 4c9fede..970dccb 100644
--- a/src/Presyntax/Tokens.hs
+++ b/src/Presyntax/Tokens.hs
@@ -15,6 +15,15 @@ data TokenClass
   | TokCParen
   | TokCBrace
 
+  -- {-# #-}
+  | TokOPragma
+  | TokCPragma
+
+  | TokPrim
+
+  | TokReplLet
+  | TokReplT Text
+
   | TokStar
   | TokColon
   | TokEqual
@@ -34,6 +43,9 @@ tokSize TokOParen = 1
 tokSize TokOBrace = 1
 tokSize TokCBrace = 1
 tokSize TokCParen = 1
+tokSize TokCPragma = 3
+tokSize TokOPragma = 3
+tokSize TokPrim = length "PRIMITIVE"
 tokSize TokStar = 1
 tokSize TokColon = 1
 tokSize TokEqual = 1
@@ -42,6 +54,8 @@ tokSize TokSemi = 1
 tokSize TokArrow = 2
 tokSize TokPi1 = 2
 tokSize TokPi2 = 2
+tokSize TokReplLet = 4
+tokSize (TokReplT s) = T.length s
 
 data Token
   = Token { tokenClass   :: TokenClass
diff --git a/src/Syntax.hs b/src/Syntax.hs
index 25a703d..21644aa 100644
--- a/src/Syntax.hs
+++ b/src/Syntax.hs
@@ -7,6 +7,19 @@ import Data.Text (Text)
 import Presyntax.Presyntax (Plicity(..))
 import qualified Data.Text as T
 import Data.IORef (IORef)
+import Data.Set (Set)
+import qualified Data.Set as Set
+
+data WiredIn
+  = WiType
+  | WiPretype
+  | WiInterval
+  | WiI0
+  | WiI1
+  | WiIAnd
+  | WiIOr
+  | WiINot
+  deriving (Eq, Show, Ord)
 
 data Term
   = Ref  Name
@@ -15,11 +28,18 @@ data Term
   | Pi   Plicity Text Term Term
   | Meta MV
   | Type
+  | Typeω
 
   | Sigma Text Term Term
   | Pair Term Term
   | Proj1 Term
   | Proj2 Term
+
+  | I
+  | I0 | I1
+  | IAnd Term Term
+  | IOr  Term Term
+  | INot Term
   deriving (Eq, Show, Ord)
 
 data MV =
@@ -37,11 +57,6 @@ instance Show MV where
 data Name
   = Bound   Text
   | Defined Text
-  | Builtin Text WiredIn
-  deriving (Eq, Show, Ord)
-
-data WiredIn
-  = WiType
   deriving (Eq, Show, Ord)
 
 type NFType = Value
@@ -52,26 +67,58 @@ data Value
   | VPi    Plicity Value   Closure
   | VSigma Value   Closure
   | VPair  Value   Value
-  | VType
+
+  | VType | VTypeω
+
+  | VI
+  | VI0 | VI1
+  | VIAnd Value Value
+  | VIOr  Value Value
+  | VINot Value
   deriving (Eq, Show, Ord)
 
 pattern VVar :: Name -> Value
 pattern VVar x = VNe (HVar x) []
 
-quote :: Value -> Term
-quote (VNe h sp) = foldl goSpine (goHead h) (reverse sp) where
+quoteWith :: Set Text -> Value -> Term
+quoteWith names (VNe h sp) = foldl goSpine (goHead h) (reverse sp) where
   goHead (HVar v) = Ref v
   goHead (HMeta m) = Meta m
 
-  goSpine t (PApp p v) = App p t (quote v)
+  goSpine t (PApp p v) = App p t (quoteWith names v)
   goSpine t PProj1 = Proj1 t
   goSpine t PProj2 = Proj2 t
 
-quote (VLam p (Closure n k))   = Lam p n (quote (k (VVar (Bound n))))
-quote (VPi p d (Closure n k))  = Pi p n (quote d) (quote (k (VVar (Bound n))))
-quote (VSigma d (Closure n k)) = Sigma n (quote d) (quote (k (VVar (Bound n))))
-quote (VPair a b) = Pair (quote a) (quote b)
-quote VType = Type
+quoteWith names (VLam p (Closure n k)) =
+  let n' = refresh names n
+   in Lam p n' (quoteWith (Set.insert n' names) (k (VVar (Bound n'))))
+
+quoteWith names (VPi p d (Closure n k)) =
+  let n' = refresh names n
+   in Pi p n' (quoteWith names d) (quoteWith (Set.insert n' names) (k (VVar (Bound n'))))
+
+quoteWith names (VSigma d (Closure n k)) =
+  let n' = refresh names n
+   in Sigma n' (quoteWith names d) (quoteWith (Set.insert n' names) (k (VVar (Bound n'))))
+
+quoteWith names (VPair a b) = Pair (quoteWith names a) (quoteWith names b)
+quoteWith _ VType = Type
+quoteWith _ VTypeω = Typeω
+quoteWith _ VI     = I
+quoteWith _ VI0    = I0
+quoteWith _ VI1    = I1
+quoteWith names (VIAnd x y) = IAnd (quoteWith names x) (quoteWith names y)
+quoteWith names (VIOr x y) = IOr (quoteWith names x) (quoteWith names y)
+quoteWith names (VINot x) = INot (quoteWith names x)
+
+refresh :: Set Text -> Text -> Text
+refresh s n
+  | T.singleton '_' == n = n
+  | n `Set.notMember` s = n
+  | otherwise = refresh s (n <> T.singleton '\'')
+
+quote :: Value -> Term
+quote = quoteWith mempty
 
 data Closure
   = Closure
diff --git a/src/Syntax/Pretty.hs b/src/Syntax/Pretty.hs
new file mode 100644
index 0000000..85471d8
--- /dev/null
+++ b/src/Syntax/Pretty.hs
@@ -0,0 +1,82 @@
+{-# OPTIONS_GHC -Wno-orphans #-}
+{-# LANGUAGE ViewPatterns #-}
+module Syntax.Pretty where
+
+import Control.Arrow (Arrow(first))
+
+import qualified Data.Text.Lazy as L
+import qualified Data.Text as T
+import Data.Text (Text)
+
+import Presyntax.Presyntax (Plicity(..))
+
+import Prettyprinter.Render.Terminal
+import Prettyprinter
+
+import Syntax
+
+instance Pretty Name where
+  pretty (Bound x)     = pretty x
+  pretty (Defined x)   = pretty x
+
+prettyTm :: Term -> Doc AnsiStyle
+prettyTm (Ref v) = pretty v
+
+prettyTm (App Im f x) = parenFun f <+> braces (prettyTm x)
+prettyTm (App Ex f x) = parenFun f <+> parenArg x
+
+prettyTm (Pair x y) = parens $ prettyTm x <> operator comma <+> prettyTm y
+prettyTm (Proj1 x) = prettyTm x <> operator (pretty ".1")
+prettyTm (Proj2 x) = prettyTm x <> operator (pretty ".2")
+
+prettyTm l@(Lam _ _ _) = pretty '\\' <> hsep (map prettyArgList al) <+> pretty "->" <+> prettyTm bod where
+  unwindLam (Lam p x y) = first ((p, x):) (unwindLam y)
+  unwindLam t = ([], t)
+
+  (al, bod) = unwindLam l
+
+  prettyArgList (Ex, v) = pretty v
+  prettyArgList (Im, v) = braces (pretty v)
+
+prettyTm (Meta x) = keyword $ pretty '?' <> pretty (mvName x)
+prettyTm Type{}  = keyword $ pretty "Type"
+prettyTm Typeω{} = keyword $ pretty "Typeω"
+prettyTm I{}     = keyword $ pretty "I"
+prettyTm I0{}    = keyword $ pretty "i0"
+prettyTm I1{}    = keyword $ pretty "i1"
+
+prettyTm (Pi Ex (T.unpack -> "_") d r) = prettyDom d <+> pretty "->" <+> prettyTm r
+prettyTm (Pi Im v d r)                 = braces (pretty v <+> colon <+> prettyTm d) <+> pretty "->" <+> prettyTm r
+prettyTm (Pi Ex v d r)                 = parens (pretty v <+> colon <+> prettyTm d) <+> pretty "->" <+> prettyTm r
+
+prettyTm (Sigma (T.unpack -> "_") d r) = prettyDom d <+> pretty "*" <+> prettyTm r
+prettyTm (Sigma v d r)                 = parens (pretty v <+> colon <+> prettyTm d) <+> pretty "*" <+> prettyTm r
+
+prettyTm (IAnd x y) = prettyTm x <+> operator (pretty "&&") <+> prettyTm y
+prettyTm (IOr x y) = prettyTm x <+> operator (pretty "||") <+> prettyTm y
+prettyTm (INot x) = operator (pretty '~') <> prettyTm x
+
+keyword :: Doc AnsiStyle -> Doc AnsiStyle
+keyword = annotate (color Magenta)
+
+operator :: Doc AnsiStyle -> Doc AnsiStyle
+operator = annotate (color Yellow)
+
+parenArg :: Term -> Doc AnsiStyle
+parenArg x@App{} = parens (prettyTm x)
+parenArg x = prettyDom x
+
+prettyDom :: Term -> Doc AnsiStyle
+prettyDom x@Pi{}    = parens (prettyTm x)
+prettyDom x@Sigma{} = parens (prettyTm x)
+prettyDom x         = parenFun x
+
+parenFun :: Term -> Doc AnsiStyle
+parenFun x@Lam{} = parens $ prettyTm x
+parenFun x = prettyTm x
+
+render :: Doc AnsiStyle -> Text
+render = L.toStrict . renderLazy . layoutPretty defaultLayoutOptions
+
+showValue :: Value -> String
+showValue = L.unpack . renderLazy . layoutPretty defaultLayoutOptions . prettyTm . quote
diff --git a/test.tt b/test.tt
new file mode 100644
index 0000000..8b545ae
--- /dev/null
+++ b/test.tt
@@ -0,0 +1,17 @@
+{-# PRIMITIVE pretype Pretype #-}
+I : Pretype
+{-# PRIMITIVE interval I #-}
+
+i0 : I
+i1 : I
+{-# PRIMITIVE i0 #-}
+{-# PRIMITIVE i1 #-}
+
+iand : I -> I -> I
+{-# PRIMITIVE iand #-}
+
+ior : I -> I -> I
+{-# PRIMITIVE ior #-}
+
+inot : I -> I
+{-# PRIMITIVE inot #-}
\ No newline at end of file