Add %default-prec.

src/parse-gram.y

@@ -115,6 +115,7 @@ int current_prec = 0;
 
 %token
   PERCENT_DEBUG           "%debug"
+  PERCENT_DEFAULT_PREC    "%default-prec"
   PERCENT_DEFINE          "%define"
   PERCENT_DEFINES         "%defines"
   PERCENT_ERROR_VERBOSE   "%error-verbose"
@@ -240,6 +241,13 @@ grammar_declaration:
 	symbol_printer_set (list->sym, $1, list->location);
       symbol_list_free ($2);
     }
+| "%default-prec" INT
+    {
+      if (0 <= $2 && $2 <= 1)
+	default_prec = $2;
+      else
+	complain_at (@1, _("invalid value for `%default-prec'"));
+    }
 ;
 
 symbol_declaration:

src/reader.c

@@ -41,6 +41,9 @@ merger_list *merge_functions;
 
 /* Has %union been seen?  */
 bool typed = false;
+
+/* Should rules have a default precedence?  */
+bool default_prec = true;
 
 /*-----------------------.
 | Set the start symbol.  |
@@ -409,7 +412,7 @@ packgram (void)
 	  ritem[itemno++] = symbol_number_as_item_number (p->sym->number);
 	  /* A rule gets by default the precedence and associativity
 	     of the last token in it.  */
-	  if (p->sym->class == token_sym)
+	  if (p->sym->class == token_sym && default_prec)
 	    rules[ruleno].prec = p->sym;
 	  if (p)
 	    p = p->next;

src/reader.h

@@ -73,5 +73,6 @@ void free_merger_functions (void);
 extern merger_list *merge_functions;
 
 extern bool typed;
+extern bool default_prec;
 
 #endif /* !READER_H_ */

src/scan-gram.l

@@ -182,6 +182,7 @@ splice	 (\\[ \f\t\v]*\n)*
 {
   "%binary"               return PERCENT_NONASSOC;
   "%debug"                return PERCENT_DEBUG;
+  "%default"[-_]"prec"    return PERCENT_DEFAULT_PREC;
   "%define"               return PERCENT_DEFINE;
   "%defines"              return PERCENT_DEFINES;
   "%destructor"		  token_type = PERCENT_DESTRUCTOR; BEGIN SC_PRE_CODE;