diff --git a/fib.ss b/fib.ss
new file mode 100644
index 0000000..c148ef9
--- /dev/null
+++ b/fib.ss
@@ -0,0 +1 @@
+(define fix (lambda (f)((lambda (x) (f (lambda (a) ((x x) a))))(lambda (x) (f (lambda (a) ((x x) a)))))))(fix (lambda (x0) (lambda (x1) (if (> 2 x1) 1 (+ (x0 (- x1 1)) (x0 (- x1 2)))))))
diff --git a/flake.nix b/flake.nix
index ecc8eb4..9c8195c 100644
--- a/flake.nix
+++ b/flake.nix
@@ -9,9 +9,7 @@
     flake-utils.lib.eachDefaultSystem (sys:
       let pkgs = import nixpkgs { system = sys; };
           hpkgs = pkgs.haskell.packages.ghc965;
-          project = (hpkgs.callCabal2nix "gecco" ./. {}).overrideAttrs (old: old // {
-            nativeBuildInputs = old.nativeBuildInputs ++ [ pkgs.llvm_15 ];
-          });
+          project = hpkgs.callCabal2nix "gecco" ./. {};
       in {
         packages.default = project;
         devShells.default = pkgs.mkShell {
diff --git a/gecco.cabal b/gecco.cabal
index 276f215..f746309 100644
--- a/gecco.cabal
+++ b/gecco.cabal
@@ -12,25 +12,23 @@ executable gecco
     main-is:          Main.hs
 
     build-depends:    base
-                    , relude
                     , gecco
-    mixins:           base hiding (Prelude)
-                    , relude (Relude as Prelude)
-                    , relude
     hs-source-dirs:   app
     default-language: GHC2021
-    default-extensions:       OverloadedStrings
-    ghc-options:      -O2 -fexpose-all-unfoldings -fspecialize-aggressively -fllvm -threaded "-with-rtsopts=-A32M -N8"
+    default-extensions: LambdaCase
+    ghc-options:      -O2 -fexpose-all-unfoldings -fspecialize-aggressively -threaded "-with-rtsopts=-A32M -N8"
 
 
 library
     exposed-modules:  Core
+                    , Val
+                    , Syn
+                    , Eval
+                    , Type
+                    , TestProg
+                    , CompChez
     build-depends:    base
-                    , relude
-    mixins:           base hiding (Prelude)
-                    , relude (Relude as Prelude)
-                    , relude
     hs-source-dirs:   src
     default-language: GHC2021
-    default-extensions:       OverloadedStrings
-    ghc-options:      -O2 -fexpose-all-unfoldings -fspecialize-aggressively -fllvm -threaded
+    default-extensions: LambdaCase
+    ghc-options:      -O2 -fexpose-all-unfoldings -fspecialize-aggressively -threaded
diff --git a/src/CompChez.hs b/src/CompChez.hs
new file mode 100644
index 0000000..6bbd646
--- /dev/null
+++ b/src/CompChez.hs
@@ -0,0 +1,43 @@
+module CompChez (comp) where
+
+import Syn
+
+name :: Int -> String
+name n = "x" ++ show n
+
+comp :: Syn -> String
+comp = (prelude ++) . go 0
+  where
+    prelude :: String
+    prelude = 
+      "(define fix (lambda (f)" ++
+        "((lambda (x) (f (lambda (a) ((x x) a))))" ++
+         "(lambda (x) (f (lambda (a) ((x x) a)))))))"
+
+    go :: Int -> Syn -> String
+    go l = \case
+      Var i -> name (l - i - 1)
+      Lam body -> "(lambda (" ++ name l ++ ") " ++ go (l+1) body ++ ")"
+      App f x -> "(" ++ go l f ++ " " ++ go l x ++ ")"
+      Let _ x body -> "(let ((" ++ name l ++ " " ++ go l x ++ ")) " ++ go (l+1) body ++ ")"
+      If p a b -> "(if " ++ go l p ++ " " ++ go l a ++ " " ++ go l b ++ ")"
+      IL i -> show i
+      BL True -> "#t"
+      BL False -> "#f"
+      UL -> "'unit"
+      Or a b -> compDyadic l "or" a b
+      And a b -> compDyadic l "and" a b
+      Not a -> "(not " ++ go l a ++ ")"
+      Add a b -> compDyadic l "+" a b
+      Sub a b -> compDyadic l "-" a b
+      Mul a b -> compDyadic l "*" a b
+      Div a b -> compDyadic l "quotient" a b
+      Mod a b -> compDyadic l "modulo" a b
+      Great a b -> compDyadic l ">" a b
+      Equal a b -> compDyadic l "equal?" a b
+      Fix f -> "(fix " ++ go l f ++ ")"
+
+
+    compDyadic :: Int -> String -> Syn -> Syn -> String
+    compDyadic l s a b = "(" ++ s ++ " " ++ go l a ++ " " ++ go l b ++ ")"
+
diff --git a/src/Eval.hs b/src/Eval.hs
new file mode 100644
index 0000000..47db79f
--- /dev/null
+++ b/src/Eval.hs
@@ -0,0 +1,38 @@
+module Eval where
+
+import Syn
+import Val
+
+eval :: Ctx -> Syn -> Val
+eval ctx (Var i) = ctx !! i
+eval ctx (Lam body) = Clos (\val -> eval (val : ctx) body)
+eval ctx (App f x) = let (Clos body) = eval ctx f
+                         x' = eval ctx x
+                      in body x'
+eval ctx (Let _ t body) = eval (eval ctx t : ctx) body
+eval ctx (If p a b) = case eval ctx p of
+  B True  -> eval ctx a
+  B False  -> eval ctx b
+eval ctx (IL i) = I i
+eval ctx (BL b) = B b
+eval ctx UL = U
+eval ctx (Or a b) = case eval ctx a of
+  B True  -> B True
+  B False -> eval ctx b
+eval ctx (And a b) = case eval ctx a of
+  B False -> B False
+  B True  -> eval ctx b
+eval ctx (Not a) = case eval ctx a of
+  B True  -> B False
+  B False -> B True
+eval ctx (Add a b) = let (I n, I m) = (eval ctx a, eval ctx b) in I (n + m)
+eval ctx (Sub a b) = let (I n, I m) = (eval ctx a, eval ctx b) in I (n - m)
+eval ctx (Mul a b) = let (I n, I m) = (eval ctx a, eval ctx b) in I (n * m)
+eval ctx (Div a b) = let (I n, I m) = (eval ctx a, eval ctx b) in I (div n m)
+eval ctx (Mod a b) = let (I n, I m) = (eval ctx a, eval ctx b) in I (mod n m)
+eval ctx (Great a b) = let (I n, I m) = (eval ctx a, eval ctx b) in B (n > m)
+eval ctx (Equal a b) = case (eval ctx a, eval ctx b) of
+  (I n, I m) -> B (n == m)
+  (B a, B b) -> B (a == b)
+  (U, U) -> B True
+eval ctx (Fix a) = eval ctx (App a (Fix a))
diff --git a/src/Syn.hs b/src/Syn.hs
new file mode 100644
index 0000000..7055817
--- /dev/null
+++ b/src/Syn.hs
@@ -0,0 +1,30 @@
+module Syn where
+
+data Syn
+  = Var Int
+  | Lam Syn
+  | App Syn Syn
+  | Let {- name :-} Ty {-=-} Syn {-in-} Syn
+  | If Syn Syn Syn
+  | IL Int
+  | BL Bool
+  | UL
+  | Or Syn Syn
+  | And Syn Syn
+  | Not Syn
+  | Add Syn Syn
+  | Sub Syn Syn
+  | Mul Syn Syn
+  | Div Syn Syn
+  | Mod Syn Syn
+  | Great Syn Syn
+  | Equal Syn Syn
+  | Fix Syn
+  deriving Show
+
+data Ty
+  = Unit
+  | Int
+  | Bool
+  | Fun Ty Ty
+  deriving (Eq, Show)
diff --git a/src/TestProg.hs b/src/TestProg.hs
new file mode 100644
index 0000000..d80f212
--- /dev/null
+++ b/src/TestProg.hs
@@ -0,0 +1,15 @@
+module TestProg where
+
+import Syn
+import Val
+import Eval
+
+fib :: Syn
+fib = Fix (Lam (Lam -- f, x
+  (If (Great (IL 2) (Var 0)) 
+      (IL 1)
+      (Add (App (Var 1) (Sub (Var 0) (IL 1)))
+           (App (Var 1) (Sub (Var 0) (IL 2)))))))
+
+vFib :: Val -> Val
+(Clos vFib) = eval [] fib
diff --git a/src/Type.hs b/src/Type.hs
new file mode 100644
index 0000000..2e42b04
--- /dev/null
+++ b/src/Type.hs
@@ -0,0 +1,63 @@
+module Type where
+
+import Syn
+import Control.Applicative
+import Control.Monad (guard)
+
+type Ctx = [Ty]
+
+check :: Ctx -> Syn -> Ty -> Maybe ()
+check ctx tr ty = case tr of
+  Lam body -> case ty of
+    Fun t1 t2 -> check (t1 : ctx) body t2
+    _ -> Nothing
+  App f x -> (infer ctx x >>= check ctx f . (`Fun` ty))
+         <|> (infer ctx f >>= \case
+                  Fun t1 t2 -> guard (t2 == ty) >> check ctx x t1
+                  _         -> Nothing
+             )
+  Let t x body -> check ctx x t >> check (t : ctx) body ty
+  If p a b -> do
+    check ctx p Bool 
+    check ctx a ty
+    check ctx b ty
+  Fix f -> check ctx f (Fun ty ty)
+  _ -> guard . (==ty) =<< infer ctx tr
+
+infer :: Ctx -> Syn -> Maybe Ty
+infer ctx tr = case tr of
+  Var i -> guard (i < length ctx) >> pure (ctx !! i)
+  App f x -> infer ctx f >>= \case
+    Fun t1 t2 -> check ctx x t1 >> pure t2
+    _ -> Nothing
+  Let t x body -> check ctx x t >> infer (t : ctx) body
+  If p a b -> do
+    check ctx p Bool
+    aty <- infer ctx a
+    bty <- infer ctx b
+    guard (aty == bty)
+    pure aty
+  IL _ -> pure Int
+  BL _ -> pure Bool
+  UL -> pure Unit
+  Or a b -> checkOp ctx a b Bool Bool
+  And a b -> checkOp ctx a b Bool Bool
+  Not a -> check ctx a Bool >> pure Bool
+  Add a b -> checkOp ctx a b Int Int
+  Sub a b -> checkOp ctx a b Int Int
+  Mul a b -> checkOp ctx a b Int Int
+  Div a b -> checkOp ctx a b Int Int
+  Mod a b -> checkOp ctx a b Int Int
+  Great a b ->  checkOp ctx a b Int Bool
+  Equal a b ->  checkOp ctx a b Int Bool
+            <|> checkOp ctx a b Bool Bool
+            <|> checkOp ctx a b Unit Bool
+  Fix f -> infer ctx f >>= \case
+    Fun t1 t2 -> guard (t1 == t2) >> pure t1
+    _         -> Nothing
+  where
+    checkOp :: Ctx -> Syn -> Syn -> Ty -> Ty -> Maybe Ty
+    checkOp ctx a b tyin tyout = do
+      check ctx a tyin
+      check ctx b tyin
+      pure tyout
diff --git a/src/Val.hs b/src/Val.hs
new file mode 100644
index 0000000..a40bb1f
--- /dev/null
+++ b/src/Val.hs
@@ -0,0 +1,15 @@
+module Val where
+
+data Val
+  = I Int
+  | B Bool
+  | U
+  | Clos (Val -> Val)
+
+instance Show Val where
+  show (I i) = "I " ++ show i
+  show (B b) = "B " ++ show b
+  show U = "U"
+  show (Clos _) = "<CLOS>"
+
+type Ctx = [Val]