From 62796be35e6e768147aab70ba0beeb94c058c714 Mon Sep 17 00:00:00 2001
From: Tom Smeding <tom@tomsmeding.com>
Date: Sun, 8 Feb 2026 15:43:02 +0100
Subject: WIP (continue in UnMonoid)

---
 src/CHAD/AST.hs | 6 ++++++
 1 file changed, 6 insertions(+)

(limited to 'src/CHAD/AST.hs')

diff --git a/src/CHAD/AST.hs b/src/CHAD/AST.hs
index 3f6dfc4..bb14218 100644
--- a/src/CHAD/AST.hs
+++ b/src/CHAD/AST.hs
@@ -129,6 +129,9 @@ data Expr x env t where
   EPlus :: x t -> SMTy t -> Expr x env t -> Expr x env t -> Expr x env t
   EOneHot :: x t -> SMTy t -> SAcPrj p t a -> Expr x env (AcIdxS p t) -> Expr x env a -> Expr x env t
 
+  EIdxPair :: x (TIdxPair n t) -> SNat n -> Expr x env (Tup (Replicate n TIx)) -> Expr x env t -> Expr x env (TIdxPair n t)
+  EUnIdxPair :: x (TPair (Tup (Replicate n TIx)) t) -> Expr x env (TIdxPair n t) -> Expr x env (TPair (Tup (Replicate n TIx)) t)
+
   -- interface of abstract monoidal types
   ELNil :: x (TLEither a b) -> STy a -> STy b -> Expr x env (TLEither a b)
   ELInl :: x (TLEither a b) -> STy b -> Expr x env a -> Expr x env (TLEither a b)
@@ -601,6 +604,9 @@ makeZeroInfo = \ty reference -> ELet ext reference $ go ty (EVar ext (fromSMTy t
     go SMTMaybe{} _ = ENil ext
     go (SMTArr _ t) e = emap (go t (EVar ext (fromSMTy t) IZ)) e
     go SMTScal{} _ = ENil ext
+    go (SMTIdxPair _ t) e =
+      eunPair (EUnIdxPair ext e) $ \_ e1 e2 ->
+        EPair ext e1 (go t e2)
 
 splitSparsePair
   :: -- given a sparsity
-- 
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