From 4e9957bda4d983d667ad8a86013d766b2e013623 Mon Sep 17 00:00:00 2001
From: Tom Smeding <tom@tomsmeding.com>
Date: Sat, 14 Feb 2026 18:03:28 +0100
Subject: WIP

---
 src/CHAD/AST/UnMonoid.hs | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/src/CHAD/AST/UnMonoid.hs b/src/CHAD/AST/UnMonoid.hs
index ceb10de..cd6467c 100644
--- a/src/CHAD/AST/UnMonoid.hs
+++ b/src/CHAD/AST/UnMonoid.hs
@@ -143,8 +143,8 @@ unMonoid = \case
   EOp _ op e -> EOp ext op (unMonoid e)
   ECustom _ t1 t2 t3 a b c e1 e2 -> ECustom ext (tUnMonoid t1) (tUnMonoid t2) (tUnMonoid t3) (unMonoid a) (unMonoid b) (unMonoid c) (unMonoid e1) (unMonoid e2)
   ERecompute _ e -> ERecompute ext (unMonoid e)
-  EWith _ t a b -> EWith ext t (unMonoid a) (unMonoid b)
-  EError _ t s -> EError ext t s
+  EWith _ t a b -> EWith ext (mtUnMonoid t) (unMonoid a) (unMonoid b)
+  EError _ t s -> EError ext (tUnMonoid t) s
 
 zero :: SMTy t -> Ex env (ZeroInfo t) -> Ex env (UnMonoid t)
 -- don't destroy the effects!
@@ -289,11 +289,13 @@ accumulateSparse topty topsp arg accum = case (topty, topsp) of
               (EIdx ext (evar (IS IZ)) (EVar ext tn IZ))
               (\w prj idx val -> accum (WPop (WPop w)) (SAPArrIdx prj) (EPair ext (EVar ext tn (w @> IZ)) idx) val)) $
       ENil ext
-  (SMTArr _ t, SpArrIdx s) ->
+  (SMTArr n t, SpArrIdx SNil) -> _
+  (SMTArr n t, SpArrIdx (s `SCons` l)) ->
     eunPair arg $ \w1 e1 e2 ->
-    elet (accumulateSparse t s e2
-            (\w prj idx val -> accum (w .> w1) (SAPArrIdx prj) (EPair ext (weakenExpr w e1) idx) val)) $
-      ENil ext
+      _
+    -- elet (accumulateSparse t s e2
+    --         (\w prj idx val -> accum (w .> w1) (SAPArrIdx prj) (EPair ext (weakenExpr w e1) idx) val)) $
+    --   ENil ext
 
 acPrjCompose
   :: SAIDense dense
-- 
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