* src/gram.h, src/gram.c (rules_rhs_length): New.

(ritem_longest_rhs): Use it.
* src/gram.h (rule_t): `number' is a new member.
* src/reader.c (packgram): Set it.
* src/reduce.c (reduce_grammar_tables): Move the useless rules at
the end of `rules', and count them out of `nrules'.
(reduce_output, dump_grammar): Adjust.
* src/print.c (print_grammar): It is no longer needed to check for
the usefulness of a rule, as useless rules are beyond `nrules + 1'.
* tests/reduce.at (Reduced Automaton): New test.

tests/reduce.at

@@ -173,6 +173,89 @@ AT_CLEANUP
 
 
 
+## ------------------- ##
+## Reduced Automaton.  ##
+## ------------------- ##
+
+# Check that the automaton is that as the for the grammar reduced by
+# hand.
+
+AT_SETUP([Reduced Automaton])
+
+# The non reduced grammar.
+# ------------------------
+AT_DATA([[not-reduced.y]],
+[[/* A useless token. */
+%token useless_token
+/* A useful one. */
+%token useful
+%verbose
+%output="not-reduced.c"
+
+%%
+
+exp: useful            { /* A useful action. */ }
+   | non_productive    { /* A non productive action. */ }
+   ;
+
+not_reachable: useful  { /* A not reachable action. */ }
+             ;
+
+non_productive: non_productive useless_token
+                       { /* Another non productive action. */ }
+              ;
+]])
+
+AT_CHECK([[bison not-reduced.y]], 0, [],
+[[not-reduced.y contains 2 useless nonterminals and 3 useless rules
+]])
+
+AT_CHECK([[sed -n '/^Grammar/q;/^$/!p' not-reduced.output]], 0,
+[[Useless nonterminals:
+   not_reachable
+   non_productive
+Terminals which are not used:
+   useless_token
+Useless rules:
+#2     exp: non_productive;
+#3     not_reachable: useful;
+#4     non_productive: non_productive useless_token;
+]])
+
+# The reduced grammar.
+# --------------------
+AT_DATA([[reduced.y]],
+[[/* A useless token. */
+%token useless_token
+/* A useful one. */
+%token useful
+%verbose
+%output="reduced.c"
+
+%%
+
+exp: useful            { /* A useful action. */ }
+//   | non_productive    { /* A non productive action. */ } */
+   ;
+
+//not_reachable: useful  { /* A not reachable action. */ }
+//             ;
+
+//non_productive: non_productive useless_token
+//                       { /* Another non productive action. */ }
+//              ;
+]])
+
+AT_CHECK([[bison reduced.y]])
+
+# Comparing the parsers.
+cp reduced.c expout
+AT_CHECK([sed 's/not-reduced/reduced/g' not-reduced.c], 0, [expout])
+
+AT_CLEANUP
+
+
+
 ## ------------------- ##
 ## Underivable Rules.  ##
 ## ------------------- ##