diff -r b29a65783ffe -r a1daf71787b1 src/Tools/isac/calcelems.sml
--- a/src/Tools/isac/calcelems.sml	Thu Oct 27 10:48:24 2016 +0200
+++ b/src/Tools/isac/calcelems.sml	Sat Nov 12 17:21:43 2016 +0100
@@ -135,7 +135,8 @@
 | Rls_ of rls          (*.ie. rule sets may be nested.*)
 and scr =
     EmptyScr
-  | Prog of term (* for met *)
+  | Prog of term (* a leaf is either a tactic or an 'exp' in 'let v = expr' 
+                    where 'exp' does not contain a tactic. *)
   | Rfuns of     (* for Rrls, usage see rational.sml ----- reverse rewrite -----      *)
     {init_state : (* initialise for reverse rewriting by the Interpreter              *)
       term ->         (* for this the rrlsstate is initialised:                       *)