diff --git a/regression/common.ml b/regression/common.ml
index b44940b1d..fa06cbe4e 100644
--- a/regression/common.ml
+++ b/regression/common.ml
@@ -1,6 +1,16 @@
 open GT
-open Syntax.Expr
+open Syntax
+       
+let conj = (&&)
+             
 open Embedding
 
-let state ps = List.fold_right (fun (x, v) s -> update x v s) ps empty
-let eval s e = Printf.printf "%d\n" (eval s e)
+let state ps = List.fold_right (fun (x, v) (s, p) -> Expr.update x v s, (x =:= !? v) :: p) ps (Expr.empty, [])
+let eval  (s, p) e =
+  let orig      = Expr.eval s e in
+  let stmt      = List.fold_right (fun p s -> p |> s) p (Stmt.Write e) in
+  let [s_orig]  = eval [] stmt in
+  let [sm_orig] = SM.run [] (SM.compile stmt) in
+  if conj (orig = s_orig) (orig = sm_orig)
+  then Printf.printf "%d\n" orig
+  else Printf.printf "*** divergence: %d <?> %d <?> %d\n" orig s_orig sm_orig