Comments in the engine. The issue with the very first call to the lexer

in the special case where the language is empty or {epsilon} is now fixed.

TODO

@@ -8,16 +8,6 @@
     (they need --external-tokens and --only-tokens)
   Then, one could remove Makefile.shared and ocamldep.wrapper.
 
-* engine.ml: initial call to [run env true] should be [run env false]
-    if the initial state has a default reduction on #
-    i.e. if only the empty word is accepted!
-  I think currently the code back-end is OK
-  and the table back-end is wrong (void.mly)
-    in theory, [entry] in [engine.ml]
-    should be parameterized by [please_discard]
-    which should be [false] iff the initial state
-    has a default reduction on #
-
 * Changes that could be applied to the code back-end:
     [action] could now be inlined into [run]
     [initiate] and [bookkeeping] could be merged?

src/codeBackend.ml

@@ -959,7 +959,7 @@ let runpushcellunless shiftreduce s e =
    invoke the lexer, so the [run] function for an initial state must
    do it. (Except in the very special case where the initial state
    has a default reduction on [#] -- this means the grammar recognizes
-   only the empty word.) *)
+   only the empty word. We have ruled out this case.) *)
 
 let gettoken s defred e =
   match Lr1.incoming_symbol s, defred with

src/engine.ml

@@ -343,10 +343,12 @@ module Make (T : TABLE) = struct
 
     (* Begin parsing. *)
 
+    (* The parameter [please_discard] here is [true], which means we know
+       that we must read at least one token. This claim relies on the fact
+       that we have ruled out the two special cases where a start symbol
+       recognizes the empty language or the singleton language {epsilon}. *)
+
     run env true
-      (* TEMPORARY in principle [please_discard] here should be [false]
-         if the state [s] has a default reduction on [#], that is, if
-         this starting state accepts only the empty word. *)
 
   (* [offer env triple] is invoked by the user in response to a result of the
      form [InputNeeded env]. [offer] is just a synonym for [discard]. *)