1 files changed, 7 insertions, 0 deletions
diff --git a/src/AST.hs b/src/AST.hs
index 8dfea68..5dab62f 100644
--- a/src/AST.hs
+++ b/src/AST.hs
@@ -129,6 +129,13 @@ tTup = mkTup STNil STPair
 eTup :: SList (Ex env) list -> Ex env (Tup list)
 eTup = mkTup (ENil ext) (EPair ext)
 
+unTup :: (forall a b. c (TPair a b) -> (c a, c b))
+      -> SList f list -> c (Tup list) -> SList c list
+unTup _ SNil _ = SNil
+unTup unpack (_ `SCons` list) tup =
+  let (xs, x) = unpack tup
+  in x `SCons` unTup unpack list xs
+
 type family InvTup core env where
   InvTup core '[] = core
   InvTup core (t : ts) = InvTup (TPair core t) ts