commit c49947ff0a9ded3f97d19dda2738be18a9a94828
Author: Anthony Heading <anthony.heading@localhost>
Date:   Sun Apr 3 16:33:24 2022 -0400

    Change 'private' to 'protected' to enable inheritance from the parser
    class.  Define 'api.parser.subclass' variable to have the generated
    parse() function be defined in this class.

diff --git data/skeletons/c++.m4 data/skeletons/c++.m4
index 8b30524b..10ab80ef 100644
--- data/skeletons/c++.m4
+++ data/skeletons/c++.m4
@@ -28,6 +28,7 @@ m4_include(b4_skeletonsdir/[c.m4])
 
 b4_percent_define_check_kind([api.namespace], [code], [deprecated])
 b4_percent_define_check_kind([api.parser.class], [code], [deprecated])
+b4_percent_define_check_kind([api.parser.subclass], [code], [deprecated])
 
 
 ## ----- ##
@@ -113,6 +114,8 @@ b4_percent_define_default([[define_location_comparison]],
                           [m4_if(b4_percent_define_get([[filename_type]]),
                                  [std::string], [[true]], [[false]])])
 
+b4_percent_define_default([[api.parser.subclass]],
+			  [b4_percent_define_get([[api.namespace]])[::]][b4_percent_define_get([[api.parser.class]])])
 
 
 ## ----------- ##
diff --git data/skeletons/lalr1.cc data/skeletons/lalr1.cc
index 7cb69d3d..dcbfc2e2 100644
--- data/skeletons/lalr1.cc
+++ data/skeletons/lalr1.cc
@@ -163,6 +163,8 @@ m4_pushdef([b4_copyright_years],
 
 m4_define([b4_parser_class],
           [b4_percent_define_get([[api.parser.class]])])
+m4_define([b4_parser_subclass],
+          [b4_percent_define_get([[api.parser.subclass]])])
 
 b4_bison_locations_if([# Backward compatibility.
    m4_define([b4_location_constructors])
@@ -284,13 +286,14 @@ m4_define([b4_shared_declarations],
       const symbol_type& yyla_;
     };
 ]])[
-  private:
 #if YY_CPLUSPLUS < 201103L
+  private:
     /// Non copyable.
     ]b4_parser_class[ (const ]b4_parser_class[&);
     /// Non copyable.
     ]b4_parser_class[& operator= (const ]b4_parser_class[&);
 #endif
+  protected:
 ]b4_lac_if([[
     /// Check the lookahead yytoken.
     /// \returns  true iff the token will be eventually shifted.
@@ -384,7 +387,6 @@ m4_define([b4_shared_declarations],
     template <typename Base>
     void yy_destroy_ (const char* yymsg, basic_symbol<Base>& yysym) const;
 
-  private:
     /// Type access provider for state based symbols.
     struct by_state
     {
@@ -833,14 +835,16 @@ m4_if(b4_prefix, [yy], [],
     return yyvalue == yytable_ninf_;
   }
 
+]b4_namespace_close[
+
   int
-  ]b4_parser_class[::operator() ()
+  ]b4_parser_subclass[::operator() ()
   {
     return parse ();
   }
 
   int
-  ]b4_parser_class[::parse ()
+  ]b4_parser_subclass[::parse ()
   {
     int yyn;
     /// Length of the RHS of the rule being reduced.
@@ -1198,6 +1202,8 @@ b4_dollar_popdef])[]dnl
 #endif // YY_EXCEPTIONS
   }
 
+]b4_namespace_open[
+
   void
   ]b4_parser_class[::error (const syntax_error& yyexc)
   {
diff --git src/muscle-tab.c src/muscle-tab.c
index 3d3baf13..4bfd4200 100644
--- src/muscle-tab.c
+++ src/muscle-tab.c
@@ -455,6 +455,7 @@ muscle_percent_variable_update (char const *variable,
     { "namespace",                  "api.namespace",             muscle_code },
     { "package",                    "api.package",               muscle_code },
     { "parser_class_name",          "api.parser.class",          muscle_code },
+    { "parser_subclass_name",       "api.parser.subclass",       muscle_code },
     { "public",                     "api.parser.public",         muscle_keyword },
     { "strictfp",                   "api.parser.strictfp",       muscle_keyword },
     { "stype",                      "api.value.type",            -1 },