can't do this! killing myself tonight ‼️ here's three lines of code i spent four hours on

src/Core.hs

@@ -1,14 +1,67 @@
+{-# LANGUAGE PatternSynonyms #-}
 module Core where
 ----------------------------------------------------------------------------------
+import Data.Coerce
+----------------------------------------------------------------------------------
 
-data Expr = Let Rec [Binding] Expr
-          | Case Expr [Alt]
+data Expr = Var Name
+          | Con Int Int 
+          | Let Rec [Binding] Expr
+          | Case Expr [Alter]
+          | Lam [Name] Expr
+          | App Expr Expr
+          | IntP Int
 
-data Binding
+infixl 2 :$
+pattern (:$) :: Expr -> Expr -> Expr
+pattern f :$ x = App f x
 
-data Rec
+data Binding = Binding Name Expr
 
-data Alt
+infixl 1 :=
+pattern (:=) :: Name -> Expr -> Binding
+pattern k := v = Binding k v
+
+data Rec = Rec
+         | NonRec
+
+data Alter = Alter Int [Name] Expr
 
 type Name = String
 
+data ScDef = ScDef Name [Name] Expr
+
+newtype Program = Program [ScDef]
+
+----------------------------------------------------------------------------------
+
+instance Semigroup Program where
+    (<>) = coerce $ (++) @ScDef
+
+instance Monoid Program where
+    mempty = Program []
+
+----------------------------------------------------------------------------------
+
+bindersOf :: [(Name, b)] -> [Name]
+bindersOf = fmap fst
+
+rhssOf :: [(Name, b)] -> [b]
+rhssOf = fmap snd
+
+isAtomic :: Expr -> Bool
+isAtomic (Var _) = True
+isAtomic _       = False
+
+----------------------------------------------------------------------------------
+
+corePrelude :: Program
+corePrelude = Program
+    [ ScDef "id" ["x"] (Var "x")
+    , ScDef "K" ["x", "y"] (Var "x")
+    , ScDef "K1" ["x", "y"] (Var "y")
+    , ScDef "S" ["f", "g", "x"] (Var "f" :$ Var "x" :$ (Var "g" :$ Var "x"))
+    , ScDef "compose" ["f", "g", "x"] (Var "f" :$ (Var "g" :$ Var "x"))
+    , ScDef "twice" ["f", "g", "x"] (Var "f" :$ (Var "g" :$ Var "x"))
+    ]
+