Add a visual test of [ba].

demos/basic/Main.ml

@@ -407,6 +407,14 @@ let print_fa t =
 let () =
   evaluate print_fa
 
+let print_ba t =
+  printf "ba(%a) = %a\n%!"
+    nhprint t
+    Atom.Set.print (ba_term t)
+
+let () =
+  evaluate print_ba
+
 let print_subst1 u x t =
   let t' = subst1 u x t in
   printf "substituting %a for %a in %a = ...\n  %a\n%s\n%!"