diff --git a/src/Core/Examples.hs b/src/Core/Examples.hs
index b83a21e..83b2c1a 100644
--- a/src/Core/Examples.hs
+++ b/src/Core/Examples.hs
@@ -77,3 +77,15 @@ facExample = [coreProg|
     main = fac 3;
 |]
 
+corePrelude :: Module
+corePrelude = Module (Just ("Prelude", [])) $ Program
+    [ ScDef "id" ["x"] (Var "x")
+    , ScDef "k" ["x", "y"] (Var "x")
+    , ScDef "k1" ["x", "y"] (Var "y")
+    , ScDef "succ" ["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", "x"] (Var "f" :$ (Var "f" :$ Var "x"))
+    , ScDef "False" [] $ Con 0 0
+    , ScDef "True" [] $ Con 1 0
+    ]
+
diff --git a/src/Core/Lex.x b/src/Core/Lex.x
index 8d2fc8b..0aebd64 100644
--- a/src/Core/Lex.x
+++ b/src/Core/Lex.x
@@ -139,7 +139,7 @@ data Located a = Located Int Int Int a
     deriving Show
 
 constTok :: t -> AlexInput -> Int -> Alex (Located t)
-constTok t (AlexPn _ y x,_,_,_) l = pure $ Located x y l t
+constTok t (AlexPn _ y x,_,_,_) l = pure $ Located y x l t
 
 data CoreToken = TokenLet
                | TokenLetrec
@@ -237,7 +237,7 @@ data ParseError = ParErrLexical String
                 deriving Show
 
 lexWith :: (String -> CoreToken) -> Lexer
-lexWith f (AlexPn _ y x,_,_,s) l = pure $ Located x y l (f $ take l s)
+lexWith f (AlexPn _ y x,_,_,s) l = pure $ Located y x l (f $ take l s)
 
 lexToken :: Alex (Located CoreToken)
 lexToken = alexMonadScan
@@ -250,21 +250,21 @@ getSrcCol = Alex $ \ st ->
 lbrace :: Lexer
 lbrace (AlexPn _ y x,_,_,_) l = do
     pushContext NoLayout
-    pure $ Located x y l TokenLBrace
+    pure $ Located y x l TokenLBrace
 
 rbrace :: Lexer
 rbrace (AlexPn _ y x,_,_,_) l = do
     popContext
-    pure $ Located x y l TokenRBrace
+    pure $ Located y x l TokenRBrace
 
 insRBraceV :: AlexPosn -> Alex (Located CoreToken)
 insRBraceV (AlexPn _ y x) = do
     popContext
-    pure $ Located x y 0 TokenRBraceV
+    pure $ Located y x 0 TokenRBraceV
 
 insSemi  :: AlexPosn -> Alex (Located CoreToken)
 insSemi (AlexPn _ y x) = do
-    pure $ Located x y 0 TokenSemicolon
+    pure $ Located y x 0 TokenSemicolon
 
 modifyUst :: (AlexUserState -> AlexUserState) -> Alex ()
 modifyUst f = do
@@ -282,7 +282,7 @@ noBrace :: Lexer
 noBrace (AlexPn _ y x,_,_,_) l = do
     col <- getSrcCol
     pushContext (Layout col)
-    pure $ Located x y l TokenLBraceV
+    pure $ Located y x l TokenLBraceV
 
 getOffside :: Alex Ordering
 getOffside = do
@@ -303,13 +303,13 @@ doBol (p,c,_,s) _ = do
 letin :: Lexer
 letin (AlexPn _ y x,_,_,_) l = do
     popContext
-    pure $ Located x y l TokenIn
+    pure $ Located y x l TokenIn
 
 topLevelOff :: Lexer
 topLevelOff = noBrace
 
 alexEOF :: Alex (Located CoreToken)
 alexEOF = Alex $ \ st@(AlexState { alex_pos = AlexPn _ y x }) ->
-    Right (st, Located x y 0 TokenEOF)
+    Right (st, Located y x 0 TokenEOF)
 
 }
diff --git a/src/Core/Parse.y b/src/Core/Parse.y
index ee93323..259faf3 100644
--- a/src/Core/Parse.y
+++ b/src/Core/Parse.y
@@ -138,9 +138,9 @@ Con             : '(' consym ')'                    { $2 }
 
 {
 parseError :: [Located CoreToken] -> RLPC ParseError a
-parseError (Located x y l _ : _) = addFatal err
+parseError (Located y x l _ : _) = addFatal err
     where err = SrcError
-            { _errSpan       = (x, y, l)
+            { _errSpan       = (y,x,l)
             , _errSeverity   = Error
             , _errDiagnostic = ParErrParse
             }
diff --git a/src/Core/Syntax.hs b/src/Core/Syntax.hs
index cc4aa86..18e3b7b 100644
--- a/src/Core/Syntax.hs
+++ b/src/Core/Syntax.hs
@@ -10,7 +10,6 @@ module Core.Syntax
     , ScDef(..)
     , Module(..)
     , Program(..)
-    , corePrelude
     , bindersOf
     , rhssOf
     , isAtomic
@@ -139,18 +138,6 @@ isAtomic _       = False
 
 ----------------------------------------------------------------------------------
 
-corePrelude :: Module
-corePrelude = Module (Just ("Prelude", [])) $ Program
-    [ ScDef "id" ["x"] (Var "x")
-    , ScDef "k" ["x", "y"] (Var "x")
-    , ScDef "k1" ["x", "y"] (Var "y")
-    , ScDef "succ" ["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", "x"] (Var "f" :$ (Var "f" :$ Var "x"))
-    , ScDef "False" [] $ Con 0 0
-    , ScDef "True" [] $ Con 1 0
-    ]
-
 -- TODO: export list awareness
 insertModule :: Module -> Program -> Program
 insertModule (Module _ m) p = p <> m
diff --git a/src/TIM.hs b/src/TIM.hs
index 239eaaf..0d06a2c 100644
--- a/src/TIM.hs
+++ b/src/TIM.hs
@@ -50,6 +50,7 @@ data Prim = ConP Int Int -- ConP Tag Arity
           | IntDivP
           | IntNegP
           | IntEqP
+          | CasePairP
           deriving (Show, Eq)
 
 instance Pretty Prim where
@@ -104,6 +105,7 @@ primitives =
     , ("/#",        IntDivP)
     , ("==#",       IntEqP)
     , ("if#",       IfP)
+    , ("casePair#", CasePairP)
     ]
 
 instantiate :: Expr -> TiHeap -> [(Name, Addr)] -> (TiHeap, Addr)