]> git.saurik.com Git - bison.git/blobdiff - data/lalr1.cc
Instead of using make_symbol<TOK_FOO>, generate make_FOO for each token type.
[bison.git] / data / lalr1.cc
index e76077d60eacc11e853722b02ee5e0de20baeda7..c3678887386728d64805d2ac7217748f958a86b2 100644 (file)
-m4_divert(-1)
-
 # C++ skeleton for Bison
 
-# Copyright (C) 2002, 2003, 2004, 2005, 2006 Free Software Foundation, Inc.
+# Copyright (C) 2002, 2003, 2004, 2005, 2006, 2007, 2008
+# Free Software Foundation, Inc.
 
-# This program is free software; you can redistribute it and/or modify
+# This program is free software: you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
-# the Free Software Foundation; either version 2 of the License, or
+# the Free Software Foundation, either version 3 of the License, or
 # (at your option) any later version.
-
+#
 # This program is distributed in the hope that it will be useful,
 # but WITHOUT ANY WARRANTY; without even the implied warranty of
 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 # GNU General Public License for more details.
-
+#
 # You should have received a copy of the GNU General Public License
-# along with this program; if not, write to the Free Software
-# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
-# 02110-1301  USA
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 m4_include(b4_pkgdatadir/[c++.m4])
 
+# b4_subtract(LHS, RHS)
+# ---------------------
+# Evaluate LHS - RHS if they are integer literals, otherwise expand
+# to (LHS) - (RHS).
+m4_define([b4_subtract],
+[m4_bmatch([$1$2], [^[0123456789]*$],
+           [m4_eval([$1 - $2])],
+           [($1) - ($2)])])
+
+
+# b4_args(ARG1, ...)
+# _b4_args(ARG1, ...)
+# -------------------
+# Join with comma, skipping empty arguments.
+# b4_args calls itself recursively until it sees the first non-empty
+# argument, then calls _b4_args which prepends each non-empty argument
+# with a comma.
+m4_define([b4_args],
+[m4_if([$#$1],
+       [1], [],
+       [m4_ifval([$1],
+                 [$1[]_$0(m4_shift($@))],
+                 [$0(m4_shift($@))])])])
+
+# _b4_args(ARGS1, ...)
+# --------------------
+m4_define([_b4_args],
+[m4_if([$#$1],
+       [1], [],
+       [m4_ifval([$1], [, $1])[]$0(m4_shift($@))])])
+
+
+# b4_table_define(TABLE-NAME, CONTENT)
+# ------------------------------------
+# Define "parser::yy<TABLE-NAME>_" which contents is CONTENT.
+m4_define([b4_table_define],
+[const b4_int_type_for([$2])
+  b4_parser_class_name::yy$1_[[]] =
+  {
+  $2
+  }dnl
+])
+
+# b4_symbol_value_template(VAL, [TYPE])
+# -------------------------------------
+# Same as b4_symbol_value, but used in a template method.
+m4_copy([b4_symbol_value], [b4_symbol_value_template])
+
+# How the semantic value is extracted when using variants.
+b4_variant_if([
+  # b4_symbol_value(VAL, [TYPE])
+  # ----------------------------
+  m4_define([b4_symbol_value],
+  [m4_ifval([$2],
+            [$1.as<$2>()],
+            [$1])])
+
+  # b4_symbol_value_template(VAL, [TYPE])
+  # -------------------------------------
+  # Same as b4_symbol_value, but used in a template method.
+  m4_define([b4_symbol_value_template],
+  [m4_ifval([$2],
+            [$1.template as<$2>()],
+            [$1])])
+]) # b4_variant_if
+
+
+# b4_lex_symbol_if([IF-YYLEX-RETURNS-A-COMPLETE-SYMBOL], [IF-NOT])
+# ----------------------------------------------------------------
+m4_define([b4_lex_symbol_if],
+[b4_percent_define_ifdef([[lex_symbol]], [$1], [$2])])
+
+
+# b4_assert_if([IF-ASSERTIONS-ARE-USED], [IF-NOT])
+# ------------------------------------------------
+m4_define([b4_assert_if],
+[b4_percent_define_ifdef([[assert]], [$1], [$2])])
+
+
+# b4_lhs_value([TYPE])
+# --------------------
+# Expansion of $<TYPE>$.
+m4_define([b4_lhs_value],
+[b4_symbol_value([yylhs.value], [$1])])
+
+
+# b4_lhs_location()
+# -----------------
+# Expansion of @$.
+m4_define([b4_lhs_location],
+[yylhs.location])
+
+
+# b4_rhs_data(RULE-LENGTH, NUM)
+# -----------------------------
+# Return the data corresponding to the symbol #NUM, where the current
+# rule has RULE-LENGTH symbols on RHS.
+m4_define([b4_rhs_data],
+          [yystack_@{b4_subtract($@)@}])
+
+
+# b4_rhs_state(RULE-LENGTH, NUM)
+# -----------------------------
+# The state corresponding to the symbol #NUM, where the current
+# rule has RULE-LENGTH symbols on RHS.
+m4_define([b4_rhs_state],
+          [b4_rhs_data([$1], [$2]).state])
+
+
+# b4_rhs_value(RULE-LENGTH, NUM, [TYPE])
+# --------------------------------------
+# Expansion of $<TYPE>NUM, where the current rule has RULE-LENGTH
+# symbols on RHS.
+m4_define([b4_rhs_value],
+          [b4_symbol_value([b4_rhs_data([$1], [$2]).value], [$3])])
+
+
+# b4_rhs_location(RULE-LENGTH, NUM)
+# ---------------------------------
+# Expansion of @NUM, where the current rule has RULE-LENGTH symbols
+# on RHS.
+m4_define([b4_rhs_location],
+          [b4_rhs_data([$1], [$2]).location])
+
+
+# b4_symbol_(NUM, FIELD)
+# ----------------------
+# Recover a FIELD about symbol #NUM.  Thanks to m4_indir, fails if
+# undefined.
+m4_define([b4_symbol_],
+[m4_indir([b4_symbol($1, $2)])])
+
+
+# b4_symbol(NUM, FIELD)
+# ---------------------
+# Recover a FIELD about symbol #NUM.  Thanks to m4_indir, fails if
+# undefined.  If FIELD = id, prepend the prefix.
+m4_define([b4_symbol],
+[m4_case([$2],
+         [id],    [m4_do([b4_percent_define_get([token.prefix])],
+                         [b4_symbol_([$1], [id])])],
+         [b4_symbol_($@)])])
+
+
+# b4_symbol_if(NUM, FIELD, IF-TRUE, IF-FALSE)
+# -------------------------------------------
+# If FIELD about symbol #NUM is 1 expand IF-TRUE, if is 0, expand IF-FALSE.
+# Otherwise an error.
+m4_define([b4_symbol_if],
+[m4_case(b4_symbol([$1], [$2]),
+         [1], [$3],
+         [0], [$4],
+         [m4_fatal([$0: field $2 of $1 is not a Boolean:] b4_symbol([$1], [$2]))])])
+
+
+# b4_symbol_actions(FILENAME, LINENO,
+#                   SYMBOL-TAG, SYMBOL-NUM,
+#                   SYMBOL-ACTION, SYMBOL-TYPENAME)
+# -------------------------------------------------
+# Same as in C, but using references instead of pointers.
+m4_define([b4_symbol_actions],
+[m4_pushdef([b4_dollar_dollar],
+            [b4_symbol_value_template([yysym.value], [$6])])dnl
+m4_pushdef([b4_at_dollar], [yysym.location])dnl
+      case $4: // $3
+b4_syncline([$2], [$1])
+        $5;
+b4_syncline([@oline@], [@ofile@])
+        break;
+m4_popdef([b4_at_dollar])dnl
+m4_popdef([b4_dollar_dollar])dnl
+])
+
+
+# b4_symbol_case_(SYMBOL-NUM)
+# ---------------------------
+# Issue a "case NUM" for SYMBOL-NUM.
+m4_define([b4_symbol_case_],
+[      case b4_symbol([$1], [number]): // b4_symbol([$1], [tag])
+])
+
+
+# b4_type_action_(NUMS)
+# ---------------------
+# Run actions for the symbol NUMS that all have the same type-name.
+# Skip NUMS that have no type-name.
+m4_define([b4_type_action_],
+[b4_symbol_if([$1], [has_type],
+[m4_map([b4_symbol_case_], [$@])[]dnl
+        b4_dollar_dollar([b4_symbol([$1], [number])],
+                         [b4_symbol([$1], [tag])],
+                         [b4_symbol([$1], [type])]);
+       break;
+
+])])
+
+
+# b4_symbol_constructor_declaration_(SYMBOL-NUMBER)
+# -------------------------------------------------
+# Declare the overloaded version of make_symbol for the (common) type of
+# these SYMBOL-NUMBERS.  Use at class-level.
+m4_define([b4_symbol_constructor_declaration_],
+[b4_symbol_if([$1], [is_token], [b4_symbol_if([$1], [has_id],
+[    static inline
+    symbol_type
+    make_[]b4_symbol_([$1], [id]) (dnl
+b4_args(b4_symbol_if([$1], [has_type],
+                     [const b4_symbol([$1], [type])& v]),
+        b4_locations_if([const location_type& l])));
+
+])])])
+
+
+# b4_symbol_constructor_declarations
+# ----------------------------------
+# Declare symbol constructors for all the value types.
+# Use at class-level.
+m4_define([b4_symbol_constructor_declarations],
+[b4_variant_if([
+    // Symbol constructors declarations.
+m4_map([b4_symbol_constructor_declaration_], m4_defn([b4_symbol_numbers]))])])
+
+
+
+# b4_symbol_constructor_definition_(SYMBOL-NUMBER)
+# ------------------------------------------------
+# Define symbol constructor for this SYMBOL-NUMBER.
+m4_define([b4_symbol_constructor_definition_],
+[b4_symbol_if([$1], [is_token], [b4_symbol_if([$1], [has_id],
+[  b4_parser_class_name::symbol_type
+  b4_parser_class_name::make_[]b4_symbol_([$1], [id]) (dnl
+b4_args(b4_symbol_if([$1], [has_type],
+                     [const b4_symbol([$1], [type])& v]),
+        b4_locations_if([const location_type& l])))
+  {
+    return symbol_type (b4_args([yytranslate_ (token::b4_symbol([$1], [id]))],
+                                b4_symbol_if([$1], [has_type], [v]),
+                                b4_locations_if([l])));
+  }
+
+])])])
+
+
+# b4_symbol_constructor_definitions
+# ----------------------------------
+# Define the overloaded versions of make_symbol for all the value types.
+m4_define([b4_symbol_constructor_definitions],
+[[  // symbol_base_type.
+  template <typename Exact>
+  ]b4_parser_class_name[::symbol_base_type<Exact>::symbol_base_type ()
+    : value()]b4_locations_if([
+    , location()])[
+  {
+  }]b4_locations_if([[
+
+  template <typename Exact>
+  ]b4_parser_class_name[::symbol_base_type<Exact>::symbol_base_type (const location_type& l)
+    : value()
+    , location(l)
+  {
+  }]])[
+
+  template <typename Exact>
+  ]b4_parser_class_name[::symbol_base_type<Exact>::symbol_base_type (]b4_args(
+          [const semantic_type& v],
+          b4_locations_if([const location_type& l]))[)
+    : value(v)]b4_locations_if([
+    , location(l)])[
+  {
+  }
+
+  template <typename Exact>
+  const Exact&
+  ]b4_parser_class_name[::symbol_base_type<Exact>::self () const
+  {
+    return static_cast<const Exact&>(*this);
+  }
+
+  template <typename Exact>
+  Exact&
+  ]b4_parser_class_name[::symbol_base_type<Exact>::self ()
+  {
+    return static_cast<Exact&>(*this);
+  }
+
+  template <typename Exact>
+  int
+  ]b4_parser_class_name[::symbol_base_type<Exact>::type_get () const
+  {
+    return self ().type_get_ ();
+  }
+
+  // symbol_type.
+  ]b4_parser_class_name[::symbol_type::symbol_type ()
+    : super_type ()
+    , type ()
+  {
+  }
+
+  ]b4_parser_class_name[::symbol_type::symbol_type (]b4_args(
+                [int t],
+                b4_locations_if([const location_type& l]))[)
+    : super_type (]b4_locations_if([l])[)
+    , type (t)
+  {
+  }
+
+  ]b4_parser_class_name[::symbol_type::symbol_type (]b4_args(
+                 [int t],
+                 [const semantic_type& v],
+                 b4_locations_if([const location_type& l]))[)
+    : super_type (v]b4_locations_if([, l])[)
+    , type (t)
+  {
+  }
+
+  int
+  ]b4_parser_class_name[::symbol_type::type_get_ () const
+  {
+    return type;
+  }
+]b4_lex_symbol_if([[
+  ]b4_parser_class_name[::token_type
+  ]b4_parser_class_name[::symbol_type::token () const
+  {
+    // YYTOKNUM[NUM] -- (External) token number corresponding to the
+    // (internal) symbol number NUM (which must be that of a token).  */
+    static
+    const ]b4_int_type_for([b4_toknum])[
+    yytoken_number_[] =
+    {
+  ]b4_toknum[
+    };
+    return static_cast<token_type> (yytoken_number_[type]);
+  }
+]])[
+
+]b4_variant_if(
+[  // Implementation of make_symbol for each symbol type.
+m4_map([b4_symbol_constructor_definition_], m4_defn([b4_symbol_numbers]))])])
+
+
+# b4_symbol_variant(YYTYPE, YYVAL, ACTION, [ARGS])
+# ------------------------------------------------
+# Run some ACTION ("build", or "destroy") on YYVAL of symbol type
+# YYTYPE.
+m4_define([b4_symbol_variant],
+[m4_pushdef([b4_dollar_dollar],
+            [$2.$3<$][3>(m4_shift3($@))])dnl
+  switch ($1)
+    {
+m4_map([b4_type_action_], m4_defn([b4_type_names]))[]dnl
+      default:
+        break;
+    }
+m4_popdef([b4_dollar_dollar])dnl
+])
+
+
+# _b4_char_sizeof_counter
+# -----------------------
+# A counter used by _b4_char_sizeof_dummy to create fresh symbols.
+m4_define([_b4_char_sizeof_counter],
+[0])
+
+# _b4_char_sizeof_dummy
+# ---------------------
+# At each call return a new C++ identifier.
+m4_define([_b4_char_sizeof_dummy],
+[m4_define([_b4_char_sizeof_counter], m4_incr(_b4_char_sizeof_counter))dnl
+dummy[]_b4_char_sizeof_counter])
+
+
+# b4_char_sizeof_(SYMBOL-NUM)
+# ---------------------------
+# A comment describing this symbol.
+m4_define([b4_char_sizeof_],
+[      // b4_symbol([$1], [tag])
+])
+
+# b4_char_sizeof(SYMBOL-NUMS)
+# --------------------------
+# To be mapped on the list of type names to produce:
+#
+#    char dummy1[sizeof(type_name_1)];
+#    char dummy2[sizeof(type_name_2)];
+#
+# for defined type names.
+m4_define([b4_char_sizeof],
+[b4_symbol_if([$1], [has_type],
+[
+m4_map([b4_char_sizeof_], [$@])dnl
+      char _b4_char_sizeof_dummy@{sizeof([b4_symbol([$1], [type])])@};
+])])
+
+
+# b4_yytranslate_definition
+# -------------------------
+# Define yytranslate_.  Sometimes we want it in the header file,
+# sometimes the cc file suffices.
+m4_define([b4_yytranslate_definition],
+[[  // Symbol number corresponding to token number t.
+  ]b4_parser_class_name[::token_number_type
+  ]b4_parser_class_name[::yytranslate_ (]b4_lex_symbol_if([token_type],
+                                                          [int])[ t)
+  {
+    static
+    const token_number_type
+    translate_table[] =
+    {
+]b4_translate[
+    };
+    const unsigned int user_token_number_max_ = ]b4_user_token_number_max[;
+    const token_number_type undef_token_ = ]b4_undef_token_number[;
+
+    if (static_cast<int>(t) <= yyeof_)
+      return yyeof_;
+    else if (static_cast<unsigned int> (t) <= user_token_number_max_)
+      return translate_table[t];
+    else
+      return undef_token_;
+  }
+]])
+
+
+m4_pushdef([b4_copyright_years],
+           [2002, 2003, 2004, 2005, 2006, 2007, 2008])
+
+m4_define([b4_parser_class_name],
+          [b4_percent_define_get([[parser_class_name]])])
+
 # The header is mandatory.
 b4_defines_if([],
-              [m4_fatal(b4_skeleton[: using %defines is mandatory])])
+              [b4_fatal([b4_skeleton[: using %%defines is mandatory]])])
 
-# Backward compatibility.
+b4_locations_if(
+[# Backward compatibility.
 m4_define([b4_location_constructors])
-m4_include(b4_pkgdatadir/[location.cc])
+m4_include(b4_pkgdatadir/[location.cc])])
 
 # We do want M4 expansion after # for CPP macros.
 m4_changecom()
-m4_divert(0)dnl
-b4_defines_if(
-[@output @output_header_name@
-b4_copyright([Skeleton interface for Bison LALR(1) parsers in C++],
-  [2002, 2003, 2004, 2005, 2006])
+m4_divert_push(0)dnl
+@output(b4_spec_defines_file@)@
+b4_copyright([Skeleton interface for Bison LALR(1) parsers in C++])
 dnl FIXME: This is wrong, we want computed header guards.
 [
 /* C++ LALR(1) parser skeleton written by Akim Demaille.  */
@@ -43,21 +470,117 @@ dnl FIXME: This is wrong, we want computed header guards.
 #ifndef PARSER_HEADER_H
 # define PARSER_HEADER_H
 
-]m4_ifdef([b4_start_header],
-[[/* Copy the %start-header blocks.  */
-]b4_user_start_header])[
+]b4_percent_code_get([[requires]])[
 
+]b4_assert_if([#include <cassert>])[
 #include <string>
 #include <iostream>
 #include "stack.hh"
 
-namespace ]b4_namespace[
-{
-  class position;
-  class location;
-}
+]b4_namespace_open[
+]b4_locations_if([  class position;
+  class location;])[
+]b4_variant_if(
+[[
+  /// A char[S] buffer to store and retrieve objects.
+  ///
+  /// Sort of a variant, but does not keep track of the nature
+  /// of the stored data, since that knowledge is available
+  /// via the current state.
+  template <size_t S>
+  struct variant
+  {]b4_assert_if([
+    /// Whether something is contained.
+    bool built;
+])[
+    /// Empty construction.
+    inline
+    variant ()]b4_assert_if([
+      : built(false)])[
+    {}
+
+    /// Instantiate a \a T in here.
+    template <typename T>
+    inline T&
+    build()
+    {]b4_assert_if([
+      assert(!built);
+      built = true;])[
+      return *new (buffer) T;
+    }
+
+    /// Instantiate a \a T in here from \a t.
+    template <typename T>
+    inline T&
+    build(const T& t)
+    {]b4_assert_if([
+      assert(!built);
+      built = true;])[
+      return *new (buffer) T(t);
+    }
+
+    /// Construct and fill.
+    template <typename T>
+    inline
+    variant (const T& t)]b4_assert_if([
+      : built(true)])[
+    {
+      new (buffer) T(t);
+    }
+
+    /// Accessor to a built \a T.
+    template <typename T>
+    inline T&
+    as()
+    {]b4_assert_if([
+      assert(built);])[
+      return reinterpret_cast<T&>(buffer);
+    }
+
+    /// Const accessor to a built \a T (for %printer).
+    template <typename T>
+    inline const T&
+    as() const
+    {]b4_assert_if([
+      assert(built);])[
+      return reinterpret_cast<const T&>(buffer);
+    }
+
+    /// Swap the content with \a other.
+    template <typename T>
+    inline void
+    swap(variant<S>& other)
+    {
+      std::swap(as<T>(), other.as<T>());
+    }
+
+    /// Assign the content of \a other to this.
+    /// Destroys \a other.
+    template <typename T>
+    inline void
+    build(variant<S>& other)
+    {
+      build<T>();
+      swap<T>(other);
+      other.destroy<T>();
+    }
 
-#include "location.hh"
+    /// Destroy the stored \a T.
+    template <typename T>
+    inline void
+    destroy()
+    {
+      as<T>().~T();]b4_assert_if([
+      built = false;])[
+    }
+
+    /// A buffer large enough to store any of the semantic values.
+    char buffer[S];
+  };
+]])[
+]b4_namespace_close[
+
+]b4_locations_if([#include "location.hh"])[
 
 /* Enabling traces.  */
 #ifndef YYDEBUG
@@ -77,46 +600,53 @@ namespace ]b4_namespace[
 # define YYTOKEN_TABLE ]b4_token_table[
 #endif
 
-/* YYLLOC_DEFAULT -- Set CURRENT to span from RHS[1] to RHS[N].
+]b4_locations_if([dnl
+[/* YYLLOC_DEFAULT -- Set CURRENT to span from RHS[1] to RHS[N].
    If N is 0, then set CURRENT to the empty location which ends
    the previous symbol: RHS[0] (always defined).  */
 
 #ifndef YYLLOC_DEFAULT
-# define YYLLOC_DEFAULT(Current, Rhs, N)               \
-do {                                                   \
-  if (N)                                               \
-    {                                                  \
-      (Current).begin = (Rhs)[1].begin;                        \
-      (Current).end   = (Rhs)[N].end;                  \
-    }                                                  \
-  else                                                 \
-    {                                                  \
-      (Current).begin = (Current).end = (Rhs)[0].end;  \
-    }                                                  \
+# define YYLLOC_DEFAULT(Current, Rhs, N)                        \
+do {                                                            \
+  if (N)                                                        \
+    {                                                           \
+      (Current).begin = (Rhs)[1].location.begin;                \
+      (Current).end   = (Rhs)[N].location.end;                 \
+    }                                                           \
+  else                                                          \
+    {                                                           \
+      (Current).begin = (Current).end = (Rhs)[0].location.end; \
+    }                                                           \
 } while (false)
-#endif
+#endif]])[
 
-namespace ]b4_namespace[
-{
+]b4_namespace_open[
 
   /// A Bison parser.
   class ]b4_parser_class_name[
   {
   public:
-    /// Symbol semantic values.
 #ifndef YYSTYPE
-]m4_ifdef([b4_stype],
+]b4_variant_if(
+[    /// An auxiliary type to compute the largest semantic type.
+    union union_type
+    {]m4_map([b4_char_sizeof], m4_defn([b4_type_names]))[};
+
+    /// Symbol semantic values.
+    typedef variant<sizeof(union_type)> semantic_type;],
+[    /// Symbol semantic values.
+m4_ifdef([b4_stype],
 [    union semantic_type
-b4_user_stype
-       ;],
+    {b4_user_stype
+    };],
 [m4_if(b4_tag_seen_flag, 0,
 [[    typedef int semantic_type;]],
-[[    typedef YYSTYPE semantic_type;]])])[
+[[    typedef YYSTYPE semantic_type;]])])])[
 #else
     typedef YYSTYPE semantic_type;
-#endif
+#endif]b4_locations_if([
     /// Symbol locations.
-    typedef ]b4_location_type[ location_type;
+    typedef b4_percent_define_get([[location_type]]) location_type;])[
     /// Tokens.
     struct token
     {
@@ -133,6 +663,7 @@ b4_user_stype
     /// \returns  0 iff parsing succeeded.
     virtual int parse ();
 
+#if YYDEBUG
     /// The current debugging stream.
     std::ostream& debug_stream () const;
     /// Set the current debugging stream.
@@ -144,52 +675,21 @@ b4_user_stype
     debug_level_type debug_level () const;
     /// Set the current debugging level.
     void set_debug_level (debug_level_type l);
+#endif
 
   private:
-    /// Report a syntax error.
-    /// \param loc    where the syntax error is found.
+    /// Report a syntax error.]b4_locations_if([
+    /// \param loc    where the syntax error is found.])[
     /// \param msg    a description of the syntax error.
-    virtual void error (const location_type& loc, const std::string& msg);
+    virtual void error (]b4_locations_if([const location_type& loc, ])[const std::string& msg);
 
     /// Generate an error message.
     /// \param state   the state where the error occurred.
     /// \param tok     the lookahead token.
-    virtual std::string yysyntax_error_ (int yystate]dnl
-b4_error_verbose_if([, int tok])[);
-
-#if YYDEBUG
-    /// \brief Report a symbol value on the debug stream.
-    /// \param yytype       The token type.
-    /// \param yyvaluep     Its semantic value.
-    /// \param yylocationp  Its location.
-    virtual void yy_symbol_value_print_ (int yytype,
-                                        const semantic_type* yyvaluep,
-                                        const location_type* yylocationp);
-    /// \brief Report a symbol on the debug stream.
-    /// \param yytype       The token type.
-    /// \param yyvaluep     Its semantic value.
-    /// \param yylocationp  Its location.
-    virtual void yy_symbol_print_ (int yytype,
-                                  const semantic_type* yyvaluep,
-                                  const location_type* yylocationp);
-#endif
-
+    virtual std::string yysyntax_error_ (int yystate, int tok);
 
     /// State numbers.
     typedef int state_type;
-    /// State stack type.
-    typedef stack<state_type>    state_stack_type;
-    /// Semantic value stack type.
-    typedef stack<semantic_type> semantic_stack_type;
-    /// location stack type.
-    typedef stack<location_type> location_stack_type;
-
-    /// The state stack.
-    state_stack_type yystate_stack_;
-    /// The semantic value stack.
-    semantic_stack_type yysemantic_stack_;
-    /// The location stack.
-    location_stack_type yylocation_stack_;
 
     /// Internal symbol numbers.
     typedef ]b4_int_type_for([b4_translate])[ token_number_type;
@@ -227,24 +727,14 @@ b4_error_verbose_if([, int tok])[);
 #if YYDEBUG || YYERROR_VERBOSE || YYTOKEN_TABLE
     /// For a symbol, its name in clear.
     static const char* const yytname_[];
-#endif
+#endif]b4_error_verbose_if([
 
-#if YYERROR_VERBOSE
     /// Convert the symbol name \a n to a form suitable for a diagnostic.
-    virtual std::string yytnamerr_ (const char *n);
-#endif
+    static std::string yytnamerr_ (const char *n);])[
 
 #if YYDEBUG
-    /// A type to store symbol numbers and -1.
-    typedef ]b4_int_type_for([b4_rhs])[ rhs_number_type;
-    /// A `-1'-separated list of the rules' RHS.
-    static const rhs_number_type yyrhs_[];
-    /// For each rule, the index of the first RHS symbol in \a yyrhs_.
-    static const ]b4_int_type_for([b4_prhs])[ yyprhs_[];
     /// For each rule, its source line number.
     static const ]b4_int_type_for([b4_rline])[ yyrline_[];
-    /// For each scanner token number, its symbol number.
-    static const ]b4_int_type_for([b4_toknum])[ yytoken_number_[];
     /// Report on the debug stream that the rule \a r is going to be reduced.
     virtual void yy_reduce_print_ (int r);
     /// Print the state stack on the debug stream.
@@ -256,69 +746,177 @@ b4_error_verbose_if([, int tok])[);
 #endif
 
     /// Convert a scanner token number \a t to a symbol number.
-    token_number_type yytranslate_ (int t);
+    static inline token_number_type yytranslate_ (]b4_lex_symbol_if([token_type], [int])[ t);
+
+    /// A complete symbol, with its type.
+    template <typename Exact>
+    struct symbol_base_type
+    {
+      /// Default constructor.
+      inline symbol_base_type ();
+
+      /// Constructor.]b4_locations_if([
+      inline symbol_base_type (const location_type& l)])[;
+      inline symbol_base_type (]b4_args(
+        [const semantic_type& v],
+        b4_locations_if([const location_type& l]))[);
+
+      /// Return this with its exact type.
+      const Exact& self () const;
+      Exact& self ();
+
+      /// Return the type of this symbol.
+      int type_get () const;
+
+      /// The semantic value.
+      semantic_type value;]b4_locations_if([
+
+      /// The location.
+      location_type location;])[
+    };
+
+#if YYDEBUG
+    /// \brief Display a symbol type, value and location.
+    /// \param yyo    The output stream.
+    /// \param yysym  The symbol.
+    template <typename Exact>
+    void yy_print_ (std::ostream& yyo,
+                    const symbol_base_type<Exact>& yysym) const;
+#endif
 
     /// \brief Reclaim the memory associated to a symbol.
-    /// \param yymsg        Why this token is reclaimed.
-    /// \param yytype       The symbol type.
-    /// \param yyvaluep     Its semantic value.
-    /// \param yylocationp  Its location.
-    inline void yydestruct_ (const char* yymsg,
-                            int yytype,
-                            semantic_type* yyvaluep,
-                            location_type* yylocationp);
+    /// \param yymsg     Why this token is reclaimed.
+    ///                  If null, print nothing.
+    /// \param s         The symbol.
+    template <typename Exact>
+    inline void yy_destroy_ (const char* yymsg,
+                             symbol_base_type<Exact>& yysym) const;
+
+  public:
+    /// Element of the stack: a state and its attributes.
+    struct symbol_type : symbol_base_type<symbol_type>
+    {
+      /// The parent class.
+      typedef symbol_base_type<symbol_type> super_type;
+
+      /// Default constructor.
+      inline symbol_type ();
+
+      /// Constructor.
+      inline symbol_type (]b4_args([int t],
+                                   [const semantic_type& v],
+                                   b4_locations_if([const location_type& l]))[);
+
+      inline symbol_type (]b4_args([int t],
+                                   b4_locations_if([const location_type& l]))[);
+
+      /// The symbol type.
+      int type;
+
+      /// Return the type corresponding to this state.
+      inline int type_get_ () const;
+
+      /// Its token.
+      inline token_type token () const;
+    };
+
+]b4_symbol_constructor_declarations[
+
+  private:
+    /// Element of the stack: a state and its attributes.
+    struct stack_symbol_type : symbol_base_type<stack_symbol_type>
+    {
+      /// The parent class.
+      typedef symbol_base_type<stack_symbol_type> super_type;
+
+      /// Default constructor.
+      inline stack_symbol_type ();
+
+      /// Constructor.
+      inline stack_symbol_type (]b4_args([state_type s],
+                                         [const semantic_type& v],
+                                         b4_locations_if([const location_type& l]))[);
+
+      /// The state.
+      state_type state;
+
+      /// Return the type corresponding to this state.
+      inline int type_get_ () const;
+    };
+
+    /// Stack type.
+    typedef stack<stack_symbol_type> stack_type;
+
+    /// The stack.
+    stack_type yystack_;
+
+    /// Push a new state on the stack.
+    /// \param m    a debug message to display
+    ///             if null, no trace is output.
+    /// \param s    the symbol
+    /// \warning the contents of \a s.value is stolen.
+    inline void yypush_ (const char* m, stack_symbol_type& s);
+
+    /// Push a new look ahead token on the state on the stack.
+    /// \param m    a debug message to display
+    ///             if null, no trace is output.
+    /// \param s    the state
+    /// \param sym  the symbol (for its value and location).
+    /// \warning the contents of \a s.value is stolen.
+    inline void yypush_ (const char* m, state_type s, symbol_type& sym);
 
     /// Pop \a n symbols the three stacks.
     inline void yypop_ (unsigned int n = 1);
 
     /* Constants.  */
-    static const int yyeof_;
-    /* LAST_ -- Last index in TABLE_.  */
-    static const int yylast_;
-    static const int yynnts_;
-    static const int yyempty_;
-    static const int yyfinal_;
-    static const int yyterror_;
-    static const int yyerrcode_;
-    static const int yyntokens_;
-    static const unsigned int yyuser_token_number_max_;
-    static const token_number_type yyundef_token_;
+    enum
+    {
+      yyeof_ = 0,
+      yylast_ = ]b4_last[,           //< Last index in yytable_.
+      yynnts_ = ]b4_nterms_number[,  //< Number of nonterminal symbols.
+      yyempty_ = -2,
+      yyfinal_ = ]b4_final_state_number[, //< Termination state number.
+      yyterror_ = 1,
+      yyerrcode_ = 256,
+      yyntokens_ = ]b4_tokens_number[,   //< Number of tokens.
+    };
+
 ]b4_parse_param_vars[
   };
-}
 
-]m4_ifset([b4_global_tokens_and_yystype],
+]b4_lex_symbol_if([b4_yytranslate_definition])[
+]b4_lex_symbol_if([b4_symbol_constructor_definitions])[
+]b4_namespace_close[
+
+]b4_percent_define_flag_if([[global_tokens_and_yystype]],
 [b4_token_defines(b4_tokens)
 
 #ifndef YYSTYPE
  /* Redirection for backward compatibility.  */
-# define YYSTYPE b4_namespace::b4_parser_class_name::semantic_type
+# define YYSTYPE b4_namespace_ref::b4_parser_class_name::semantic_type
 #endif
 ])
-m4_ifdef([b4_end_header],
-[[/* Copy the %end-header blocks.  */
-]b4_end_header])[]dnl
+b4_percent_code_get([[provides]])[]dnl
 
 [#endif /* ! defined PARSER_HEADER_H */]
-])dnl
-@output @output_parser_name@
-b4_copyright([Skeleton implementation for Bison LALR(1) parsers in C++],
-  [2002, 2003, 2004, 2005, 2006])
+@output(b4_parser_file_name@)@
+b4_copyright([Skeleton implementation for Bison LALR(1) parsers in C++])
+b4_percent_code_get([[top]])[]dnl
 m4_if(b4_prefix, [yy], [],
 [
 // Take the name prefix into account.
 #define yylex   b4_prefix[]lex])[
 
 /* First part of user declarations.  */
-]b4_pre_prologue
+]b4_user_pre_prologue[
 
-b4_defines_if([
-#include @output_header_name@])[
+#include "@basename(]b4_spec_defines_file[@)"
 
 /* User implementation prologue.  */
-]b4_user_post_prologue[
+]b4_user_post_prologue
+b4_percent_code_get[]dnl
 
-#ifndef YY_
+[#ifndef YY_
 # if YYENABLE_NLS
 #  if ENABLE_NLS
 #   include <libintl.h> /* FIXME: INFRINGES ON USER NAME SPACE */
@@ -339,44 +937,46 @@ b4_defines_if([
 /* A pseudo ostream that takes yydebug_ into account.  */
 # define YYCDEBUG if (yydebug_) (*yycdebug_)
 
-# define YY_SYMBOL_PRINT(Title, Type, Value, Location) \
-do {                                                   \
-  if (yydebug_)                                                \
-    {                                                  \
-      *yycdebug_ << Title << ' ';                      \
-      yy_symbol_print_ ((Type), (Value), (Location));  \
-      *yycdebug_ << std::endl;                         \
-    }                                                  \
-} while (false)
+# define YY_SYMBOL_PRINT(Title, Symbol)         \
+  do {                                          \
+    if (yydebug_)                               \
+    {                                           \
+      *yycdebug_ << Title << ' ';               \
+      yy_print_ (*yycdebug_, Symbol);           \
+      *yycdebug_ << std::endl;                  \
+    }                                           \
+  } while (false)
 
 # define YY_REDUCE_PRINT(Rule)         \
-do {                                   \
-  if (yydebug_)                                \
-    yy_reduce_print_ (Rule);           \
-} while (false)
+  do {                                 \
+    if (yydebug_)                       \
+      yy_reduce_print_ (Rule);         \
+  } while (false)
 
 # define YY_STACK_PRINT()              \
-do {                                   \
-  if (yydebug_)                                \
-    yystack_print_ ();                 \
-} while (false)
+  do {                                 \
+    if (yydebug_)                       \
+      yystack_print_ ();                \
+  } while (false)
 
 #else /* !YYDEBUG */
 
 # define YYCDEBUG if (false) std::cerr
-# define YY_SYMBOL_PRINT(Title, Type, Value, Location)
-# define YY_REDUCE_PRINT(Rule)
-# define YY_STACK_PRINT()
+# define YY_SYMBOL_PRINT(Title, Symbol)  static_cast<void>(0)
+# define YY_REDUCE_PRINT(Rule)           static_cast<void>(0)
+# define YY_STACK_PRINT()                static_cast<void>(0)
 
 #endif /* !YYDEBUG */
 
-#define YYACCEPT       goto yyacceptlab
-#define YYABORT                goto yyabortlab
-#define YYERROR                goto yyerrorlab
+#define yyerrok         (yyerrstatus_ = 0)
+#define yyclearin       (yyempty = true)
 
-namespace ]b4_namespace[
-{
-#if YYERROR_VERBOSE
+#define YYACCEPT        goto yyacceptlab
+#define YYABORT         goto yyabortlab
+#define YYERROR         goto yyerrorlab
+#define YYRECOVERING()  (!!yyerrstatus_)
+
+]b4_namespace_open[]b4_error_verbose_if([[
 
   /* Return YYSTR after stripping away unnecessary quotes and
      backslashes, so that it's suitable for yyerror.  The heuristic is
@@ -414,8 +1014,7 @@ namespace ]b4_namespace[
 
     return yystr;
   }
-
-#endif
+]])[
 
   /// Build a parser object.
   ]b4_parser_class_name::b4_parser_class_name[ (]b4_parse_param_decl[)]m4_ifset([b4_parse_param], [
@@ -431,62 +1030,116 @@ namespace ]b4_namespace[
   {
   }
 
-#if YYDEBUG
-  /*--------------------------------.
-  | Print this symbol on YYOUTPUT.  |
-  `--------------------------------*/
 
-  inline void
-  ]b4_parser_class_name[::yy_symbol_value_print_ (int yytype,
-                          const semantic_type* yyvaluep, const location_type* yylocationp)
+  /*---------------.
+  | Symbol types.  |
+  `---------------*/
+
+]b4_lex_symbol_if([], [b4_symbol_constructor_definitions])[
+
+  // stack_symbol_type.
+  ]b4_parser_class_name[::stack_symbol_type::stack_symbol_type ()
+    : super_type ()
+    , state ()
   {
-    YYUSE (yylocationp);
-    YYUSE (yyvaluep);
-    switch (yytype)
-      {
-  ]m4_map([b4_symbol_actions], m4_defn([b4_symbol_printers]))dnl
-[       default:
-         break;
-      }
   }
 
+  ]b4_parser_class_name[::stack_symbol_type::stack_symbol_type (]b4_args(
+                 [state_type s],
+                 [const semantic_type& v],
+                 b4_locations_if([const location_type& l]))[)
+    : super_type (v]b4_locations_if([, l])[)
+    , state (s)
+  {
+  }
 
-  void
-  ]b4_parser_class_name[::yy_symbol_print_ (int yytype,
-                          const semantic_type* yyvaluep, const location_type* yylocationp)
+  int
+  ]b4_parser_class_name[::stack_symbol_type::type_get_ () const
   {
-    *yycdebug_ << (yytype < yyntokens_ ? "token" : "nterm")
-              << ' ' << yytname_[yytype] << " ("
-              << *yylocationp << ": ";
-    yy_symbol_value_print_ (yytype, yyvaluep, yylocationp);
-    *yycdebug_ << ')';
+    return yystos_[state];
   }
-#endif
 
+
+  template <typename Exact>
   void
-  ]b4_parser_class_name[::yydestruct_ (const char* yymsg,
-                          int yytype, semantic_type* yyvaluep, location_type* yylocationp)
+  ]b4_parser_class_name[::yy_destroy_ (const char* yymsg,
+                                       symbol_base_type<Exact>& yysym) const
   {
-    YYUSE (yylocationp);
+    int yytype = yysym.type_get ();
     YYUSE (yymsg);
-    YYUSE (yyvaluep);
-
-    YY_SYMBOL_PRINT (yymsg, yytype, yyvaluep, yylocationp);
+    if (yymsg)
+      YY_SYMBOL_PRINT (yymsg, yysym);
 
+    // User destructor.
     switch (yytype)
       {
-  ]m4_map([b4_symbol_actions], m4_defn([b4_symbol_destructors]))[
+]m4_map([b4_symbol_actions], m4_defn([b4_symbol_destructors]))[
        default:
          break;
+      }]b4_variant_if([
+
+    // Type destructor.
+  b4_symbol_variant([[yytype]], [[yysym.value]], [[template destroy]])])[
+  }
+
+#if YYDEBUG
+  template <typename Exact>
+  void
+  ]b4_parser_class_name[::yy_print_ (std::ostream& yyo,
+                                     const symbol_base_type<Exact>& yysym) const
+  {
+    int yytype = yysym.type_get ();
+    yyo << (yytype < yyntokens_ ? "token" : "nterm")
+        << ' ' << yytname_[yytype] << " ("]b4_locations_if([
+        << yysym.location << ": "])[;
+    switch (yytype)
+      {
+]m4_map([b4_symbol_actions], m4_defn([b4_symbol_printers]))[
+       default:
+         break;
       }
+    yyo << ')';
+  }
+#endif
+
+  void
+  ]b4_parser_class_name[::yypush_ (const char* m, state_type s,
+                                   symbol_type& sym)
+  {
+    if (m)
+      YY_SYMBOL_PRINT (m, sym);
+]b4_variant_if(
+[[    yystack_.push (stack_symbol_type (]b4_args(
+                    [s],
+                    [semantic_type()],
+                    b4_locations_if([sym.location]))[));
+    ]b4_symbol_variant([[yystos_[s]]], [[yystack_[0].value]],
+                       [build], [sym.value])],
+[[    yystack_.push (stack_symbol_type (]b4_args(
+                      [s],
+                      [sym.value],
+                      b4_locations_if([sym.location]))[));]])[
+  }
+
+  void
+  ]b4_parser_class_name[::yypush_ (const char* m, stack_symbol_type& s)
+  {
+    if (m)
+      YY_SYMBOL_PRINT (m, s);
+]b4_variant_if(
+[[    yystack_.push (stack_symbol_type (]b4_args(
+                       [s.state],
+                       [semantic_type()],
+                       b4_locations_if([s.location]))[));
+    ]b4_symbol_variant([[yystos_[s.state]]], [[yystack_[0].value]],
+                       [build], [s.value])],
+[    yystack_.push (s);])[
   }
 
   void
   ]b4_parser_class_name[::yypop_ (unsigned int n)
   {
-    yystate_stack_.pop (n);
-    yysemantic_stack_.pop (n);
-    yylocation_stack_.pop (n);
+    yystack_.pop (n);
   }
 
 #if YYDEBUG
@@ -519,9 +1172,8 @@ namespace ]b4_namespace[
   int
   ]b4_parser_class_name[::parse ()
   {
-    /// Lookahead and lookahead in internal form.
-    int yychar = yyempty_;
-    int yytoken = 0;
+    /// Whether yyla contains a lookahead.
+    bool yyempty = true;
 
     /* State.  */
     int yyn;
@@ -532,43 +1184,39 @@ namespace ]b4_namespace[
     int yynerrs_ = 0;
     int yyerrstatus_ = 0;
 
-    /// Semantic value of the lookahead.
-    semantic_type yylval;
-    /// Location of the lookahead.
-    location_type yylloc;
+    /// The lookahead symbol.
+    symbol_type yyla;]b4_locations_if([[
+
     /// The locations where the error started and ended.
-    location yyerror_range[2];
+    stack_symbol_type yyerror_range[2];]])[
 
-    /// $$.
-    semantic_type yyval;
-    /// @@$.
-    location_type yyloc;
+    /// $$ and @@$.
+    stack_symbol_type yylhs;
 
+    /// The return value of parse().
     int yyresult;
 
     YYCDEBUG << "Starting parse" << std::endl;
 
 ]m4_ifdef([b4_initial_action], [
-m4_pushdef([b4_at_dollar],     [yylloc])dnl
-m4_pushdef([b4_dollar_dollar], [yylval])dnl
+m4_pushdef([b4_at_dollar],     [yyla.location])dnl
+m4_pushdef([b4_dollar_dollar], [yyla.value])dnl
     /* User initialization code.  */
     b4_user_initial_action
 m4_popdef([b4_dollar_dollar])dnl
 m4_popdef([b4_at_dollar])])dnl
 
-  [  /* Initialize the stacks.  The initial state will be pushed in
+  [  /* Initialize the stack.  The initial state will be set in
        yynewstate, since the latter expects the semantical and the
        location values to have been already stored, initialize these
        stacks with a primary value.  */
-    yystate_stack_ = state_stack_type (0);
-    yysemantic_stack_ = semantic_stack_type (0);
-    yylocation_stack_ = location_stack_type (0);
-    yysemantic_stack_.push (yylval);
-    yylocation_stack_.push (yylloc);
+    yystack_ = stack_type (0);
+    yypush_ (0, 0, yyla);
 
-    /* New state.  */
+    // A new state was pushed on the stack.
+    // Invariant: yystate == yystack_[0].state, i.e.,
+    // yystate was just pushed onto the state stack.
   yynewstate:
-    yystate_stack_.push (yystate);
     YYCDEBUG << "Entering state " << yystate << std::endl;
 
     /* Accept?  */
@@ -586,32 +1234,24 @@ m4_popdef([b4_at_dollar])])dnl
       goto yydefault;
 
     /* Read a lookahead token.  */
-    if (yychar == yyempty_)
-      {
-       YYCDEBUG << "Reading a token: ";
-       yychar = ]b4_c_function_call([yylex], [int],
-                                    [[YYSTYPE*], [&yylval]][]dnl
-b4_locations_if([, [[location*], [&yylloc]]])dnl
-m4_ifdef([b4_lex_param], [, ]b4_lex_param))[;
-      }
-
-
-    /* Convert token to internal form.  */
-    if (yychar <= yyeof_)
-      {
-       yychar = yytoken = yyeof_;
-       YYCDEBUG << "Now at end of input." << std::endl;
-      }
-    else
+    if (yyempty)
       {
-       yytoken = yytranslate_ (yychar);
-       YY_SYMBOL_PRINT ("Next token is", yytoken, &yylval, &yylloc);
+        YYCDEBUG << "Reading a token: ";
+]b4_lex_symbol_if(
+[        yyla = b4_c_function_call([yylex], [symbol_type],
+                                   m4_ifdef([b4_lex_param], b4_lex_param));],
+[        yyla.type = yytranslate_ (b4_c_function_call([yylex], [int],
+                                    [[YYSTYPE*], [&yyla.value]][]dnl
+b4_locations_if([, [[location*], [&yyla.location]]])dnl
+m4_ifdef([b4_lex_param], [, ]b4_lex_param)));])[
+        yyempty = false;
       }
+    YY_SYMBOL_PRINT ("Next token is", yyla);
 
-    /* If the proper action on seeing token YYTOKEN is to reduce or to
-       detect an error, take that action.  */
-    yyn += yytoken;
-    if (yyn < 0 || yylast_ < yyn || yycheck_[yyn] != yytoken)
+    /* If the proper action on seeing token YYLA.TYPE is to reduce or
+       to detect an error, take that action.  */
+    yyn += yyla.type;
+    if (yyn < 0 || yylast_ < yyn || yycheck_[yyn] != yyla.type)
       goto yydefault;
 
     /* Reduce or error.  */
@@ -619,26 +1259,22 @@ m4_ifdef([b4_lex_param], [, ]b4_lex_param))[;
     if (yyn <= 0)
       {
        if (yyn == 0 || yyn == yytable_ninf_)
-       goto yyerrlab;
+         goto yyerrlab;
        yyn = -yyn;
        goto yyreduce;
       }
 
-    /* Shift the lookahead token.  */
-    YY_SYMBOL_PRINT ("Shifting", yytoken, &yylval, &yylloc);
-
     /* Discard the token being shifted.  */
-    yychar = yyempty_;
-
-    yysemantic_stack_.push (yylval);
-    yylocation_stack_.push (yylloc);
+    yyempty = true;
 
     /* Count tokens shifted since error; after three, turn off error
        status.  */
     if (yyerrstatus_)
       --yyerrstatus_;
 
+    /* Shift the lookahead token.  */
     yystate = yyn;
+    yypush_ ("Shifting", yystate, yyla);
     goto yynewstate;
 
   /*-----------------------------------------------------------.
@@ -654,45 +1290,66 @@ m4_ifdef([b4_lex_param], [, ]b4_lex_param))[;
   | yyreduce -- Do a reduction.  |
   `-----------------------------*/
   yyreduce:
-    yylen = yyr2_[yyn];
+    yylen = yyr2_[yyn];]b4_variant_if([
+    /* Variants are always initialized to an empty instance of the
+       correct type. The default $$=$1 rule is NOT applied when using
+       variants */
+    ]b4_symbol_variant([[yyr1_@{yyn@}]], [yylhs.value], [build])[],[
     /* If YYLEN is nonzero, implement the default value of the action:
        `$$ = $1'.  Otherwise, use the top of the stack.
 
-       Otherwise, the following line sets YYVAL to garbage.
+       Otherwise, the following line sets YYLHS.VALUE to garbage.
        This behavior is undocumented and Bison
        users should not rely upon it.  */
     if (yylen)
-      yyval = yysemantic_stack_[yylen - 1];
+      yylhs.value = yystack_@{yylen - 1@}.value;
     else
-      yyval = yysemantic_stack_[0];
-
+      yylhs.value = yystack_@{0@}.value;])[
+]b4_locations_if([dnl
+[
+    // Compute the default @@$.
     {
-      slice<location_type, location_stack_type> slice (yylocation_stack_, yylen);
-      YYLLOC_DEFAULT (yyloc, slice, yylen);
-    }
+      slice<stack_symbol_type, stack_type> slice (yystack_, yylen);
+      YYLLOC_DEFAULT (yylhs.location, slice, yylen);
+    }]])[
+
+    // Perform the reduction.
     YY_REDUCE_PRINT (yyn);
     switch (yyn)
       {
-       ]b4_user_actions[
-       default: break;
+]b4_user_actions[
+       default:
+          break;
       }
-    YY_SYMBOL_PRINT ("-> $$ =", yyr1_[yyn], &yyval, &yyloc);
+    // Compute post-reduction state.
+    yyn = yyr1_[yyn];
+    yystate = yypgoto_[yyn - yyntokens_] + yystack_[yylen].state;
+    if (0 <= yystate && yystate <= yylast_
+       && yycheck_[yystate] == yystack_[yylen].state)
+      yystate = yytable_[yystate];
+    else
+      yystate = yydefgoto_[yyn - yyntokens_];
+    yylhs.state = yystate;
+    YY_SYMBOL_PRINT ("-> $$ =", yylhs);
+]b4_variant_if([[
+    // Destroy the lhs symbols.
+    for (int i = 0; i < yylen; ++i)
+      // Destroy a variant which value may have be swapped with
+      // yylhs.value.  The value of yylhs.value (hence maybe one of
+      // these lhs symbols) depends on what does the default
+      // contruction for this type.  In the case of pointers for
+      // instance, nothing is done, so the value is junk.  Therefore
+      // do not try to report the content in the debug trace, it's
+      // junk.  Hence yymsg = 0.  Besides, that keeps exactly the same
+      // traces as with the other Bison skeletons.
+      yy_destroy_ (0, yystack_[i]);]])[
 
     yypop_ (yylen);
     yylen = 0;
     YY_STACK_PRINT ();
 
-    yysemantic_stack_.push (yyval);
-    yylocation_stack_.push (yyloc);
-
     /* Shift the result of the reduction.  */
-    yyn = yyr1_[yyn];
-    yystate = yypgoto_[yyn - yyntokens_] + yystate_stack_[0];
-    if (0 <= yystate && yystate <= yylast_
-       && yycheck_[yystate] == yystate_stack_[0])
-      yystate = yytable_[yystate];
-    else
-      yystate = yydefgoto_[yyn - yyntokens_];
+    yypush_ (0, yylhs);
     goto yynewstate;
 
   /*------------------------------------.
@@ -703,26 +1360,24 @@ m4_ifdef([b4_lex_param], [, ]b4_lex_param))[;
     if (!yyerrstatus_)
       {
        ++yynerrs_;
-       error (yylloc, yysyntax_error_ (yystate]dnl
-b4_error_verbose_if([, yytoken])[));
+       error (]b4_args(b4_locations_if([yyla.location]),
+                        [yysyntax_error_ (yystate, yyla.type)])[);
       }
 
-    yyerror_range[0] = yylloc;
+]b4_locations_if([[
+    yyerror_range[0].location = yyla.location;]])[
     if (yyerrstatus_ == 3)
       {
        /* If just tried and failed to reuse lookahead token after an
-        error, discard it.  */
-
-       if (yychar <= yyeof_)
-         {
-         /* Return failure if at end of input.  */
-         if (yychar == yyeof_)
-           YYABORT;
-         }
-       else
-         {
-           yydestruct_ ("Error: discarding", yytoken, &yylval, &yylloc);
-           yychar = yyempty_;
+           error, discard it.  */
+
+        /* Return failure if at end of input.  */
+        if (yyla.type == yyeof_)
+          YYABORT;
+        else
+          {
+            yy_destroy_ ("Error: discarding", yyla);
+            yyempty = true;
          }
       }
 
@@ -742,12 +1397,13 @@ b4_error_verbose_if([, yytoken])[));
     if (false)
       goto yyerrorlab;
 
-    yyerror_range[0] = yylocation_stack_[yylen - 1];
+]b4_locations_if([[
+    yyerror_range[0].location = yystack_[yylen - 1].location;]])[
     /* Do not reclaim the symbols of the rule which action triggered
        this YYERROR.  */
     yypop_ (yylen);
     yylen = 0;
-    yystate = yystate_stack_[0];
+    yystate = yystack_[0].state;
     goto yyerrlab1;
 
   /*-------------------------------------------------------------.
@@ -755,46 +1411,40 @@ b4_error_verbose_if([, yytoken])[));
   `-------------------------------------------------------------*/
   yyerrlab1:
     yyerrstatus_ = 3;  /* Each real token shifted decrements this.  */
+    {
+      stack_symbol_type error_token;
+      for (;;)
+        {
+          yyn = yypact_[yystate];
+          if (yyn != yypact_ninf_)
+            {
+              yyn += yyterror_;
+              if (0 <= yyn && yyn <= yylast_ && yycheck_[yyn] == yyterror_)
+                {
+                  yyn = yytable_[yyn];
+                  if (0 < yyn)
+                    break;
+                }
+            }
 
-    for (;;)
-      {
-       yyn = yypact_[yystate];
-       if (yyn != yypact_ninf_)
-       {
-         yyn += yyterror_;
-         if (0 <= yyn && yyn <= yylast_ && yycheck_[yyn] == yyterror_)
-           {
-             yyn = yytable_[yyn];
-             if (0 < yyn)
-               break;
-           }
-       }
-
-       /* Pop the current state because it cannot handle the error token.  */
-       if (yystate_stack_.height () == 1)
-       YYABORT;
-
-       yyerror_range[0] = yylocation_stack_[0];
-       yydestruct_ ("Error: popping",
-                    yystos_[yystate],
-                    &yysemantic_stack_[0], &yylocation_stack_[0]);
-       yypop_ ();
-       yystate = yystate_stack_[0];
-       YY_STACK_PRINT ();
-      }
-
-    yyerror_range[1] = yylloc;
-    // Using YYLLOC is tempting, but would change the location of
-    // the lookahead.  YYLOC is available though.
-    YYLLOC_DEFAULT (yyloc, (yyerror_range - 1), 2);
-    yysemantic_stack_.push (yylval);
-    yylocation_stack_.push (yyloc);
-
-    /* Shift the error token.  */
-    YY_SYMBOL_PRINT ("Shifting", yystos_[yyn],
-                  &yysemantic_stack_[0], &yylocation_stack_[0]);
-
-    yystate = yyn;
+          // Pop the current state because it cannot handle the error token.
+          if (yystack_.size () == 1)
+            YYABORT;
+]b4_locations_if([[
+          yyerror_range[0].location = yystack_[0].location;]])[
+          yy_destroy_ ("Error: popping", yystack_[0]);
+          yypop_ ();
+          yystate = yystack_[0].state;
+          YY_STACK_PRINT ();
+        }
+]b4_locations_if([[
+      yyerror_range[1].location = yyla.location;
+      YYLLOC_DEFAULT (error_token.location, (yyerror_range - 1), 2);]])[
+
+      /* Shift the error token.  */
+      error_token.state = yystate = yyn;
+      yypush_ ("Shifting", error_token);
+    }
     goto yynewstate;
 
     /* Accept.  */
@@ -808,18 +1458,15 @@ b4_error_verbose_if([, yytoken])[));
     goto yyreturn;
 
   yyreturn:
-    if (yychar != yyempty_)
-      yydestruct_ ("Cleanup: discarding lookahead", yytoken, &yylval, &yylloc);
+    if (!yyempty)
+      yy_destroy_ ("Cleanup: discarding lookahead", yyla);
 
     /* Do not reclaim the symbols of the rule which action triggered
        this YYABORT or YYACCEPT.  */
     yypop_ (yylen);
-    while (yystate_stack_.height () != 1)
+    while (yystack_.size () != 1)
       {
-       yydestruct_ ("Cleanup: popping",
-                  yystos_[yystate_stack_[0]],
-                  &yysemantic_stack_[0],
-                  &yylocation_stack_[0]);
+       yy_destroy_ ("Cleanup: popping", yystack_[0]);
        yypop_ ();
       }
 
@@ -828,12 +1475,11 @@ b4_error_verbose_if([, yytoken])[));
 
   // Generate an error message.
   std::string
-  ]b4_parser_class_name[::yysyntax_error_ (int yystate]dnl
-b4_error_verbose_if([, int tok])[)
+  ]b4_parser_class_name[::yysyntax_error_ (]dnl
+b4_error_verbose_if([int yystate, int yytoken],
+                    [int, int])[)
   {
-    std::string res;
-    YYUSE (yystate);
-#if YYERROR_VERBOSE
+    std::string yyres;]b4_error_verbose_if([[
     int yyn = yypact_[yystate];
     if (yypact_ninf_ < yyn && yyn <= yylast_)
       {
@@ -844,119 +1490,92 @@ b4_error_verbose_if([, int tok])[)
        /* Stay within bounds of both yycheck and yytname.  */
        int yychecklim = yylast_ - yyn + 1;
        int yyxend = yychecklim < yyntokens_ ? yychecklim : yyntokens_;
-       int count = 0;
-       for (int x = yyxbegin; x < yyxend; ++x)
-         if (yycheck_[x + yyn] == x && x != yyterror_)
-           ++count;
-
-       // FIXME: This method of building the message is not compatible
-       // with internationalization.  It should work like yacc.c does it.
-       // That is, first build a string that looks like this:
-       // "syntax error, unexpected %s or %s or %s"
-       // Then, invoke YY_ on this string.
-       // Finally, use the string as a format to output
-       // yytname_[tok], etc.
-       // Until this gets fixed, this message appears in English only.
-       res = "syntax error, unexpected ";
-       res += yytnamerr_ (yytname_[tok]);
-       if (count < 5)
-         {
-           count = 0;
-           for (int x = yyxbegin; x < yyxend; ++x)
-             if (yycheck_[x + yyn] == x && x != yyterror_)
-               {
-                 res += (!count++) ? ", expecting " : " or ";
-                 res += yytnamerr_ (yytname_[x]);
-               }
-         }
+
+        // Number of "expected" tokens.
+       size_t yycount = 0;
+        // Its maximum.
+        enum { YYERROR_VERBOSE_ARGS_MAXIMUM = 5 };
+        // Arguments of yyformat.
+        char const *yyarg[YYERROR_VERBOSE_ARGS_MAXIMUM];
+        yyarg[yycount++] = yytname_[yytoken];
+       for (int yyx = yyxbegin; yyx < yyxend; ++yyx)
+         if (yycheck_[yyx + yyn] == yyx && yyx != yyterror_)
+          {
+            if (yycount == YYERROR_VERBOSE_ARGS_MAXIMUM)
+            {
+              yycount = 1;
+              break;
+            }
+            else
+              yyarg[yycount++] = yytname_[yyx];
+          }
+
+        char const* yyformat = 0;
+        switch (yycount)
+        {
+#define YYCASE_(N, S)                           \
+          case N:                               \
+            yyformat = S;                       \
+          break
+          YYCASE_(1, YY_("syntax error, unexpected %s"));
+          YYCASE_(2, YY_("syntax error, unexpected %s, expecting %s"));
+          YYCASE_(3, YY_("syntax error, unexpected %s, expecting %s or %s"));
+          YYCASE_(4, YY_("syntax error, unexpected %s, expecting %s or %s or %s"));
+          YYCASE_(5, YY_("syntax error, unexpected %s, expecting %s or %s or %s or %s"));
+#undef YYCASE_
+        }
+        // Argument number.
+        size_t yyi = 0;
+        for (char const* yyp = yyformat; *yyp; ++yyp)
+          if (yyp[0] == '%' && yyp[1] == 's' && yyi < yycount)
+          {
+            yyres += yytnamerr_ (yyarg[yyi++]);
+            ++yyp;
+          }
+          else
+            yyres += *yyp;
       }
     else
-#endif
-      res = YY_("syntax error");
-    return res;
+  ]])dnl
+[    yyres = YY_("syntax error");
+    return yyres;
   }
 
 
   /* YYPACT[STATE-NUM] -- Index in YYTABLE of the portion describing
      STATE-NUM.  */
   const ]b4_int_type(b4_pact_ninf, b4_pact_ninf) b4_parser_class_name::yypact_ninf_ = b4_pact_ninf[;
-  const ]b4_int_type_for([b4_pact])[
-  ]b4_parser_class_name[::yypact_[] =
-  {
-    ]b4_pact[
-  };
+  ]b4_table_define([pact], [b4_pact])[;
 
   /* YYDEFACT[S] -- default rule to reduce with in state S when YYTABLE
      doesn't specify something else to do.  Zero means the default is an
      error.  */
-  const ]b4_int_type_for([b4_defact])[
-  ]b4_parser_class_name[::yydefact_[] =
-  {
-    ]b4_defact[
-  };
+  ]b4_table_define([defact], [b4_defact])[;
 
   /* YYPGOTO[NTERM-NUM].  */
-  const ]b4_int_type_for([b4_pgoto])[
-  ]b4_parser_class_name[::yypgoto_[] =
-  {
-    ]b4_pgoto[
-  };
+  ]b4_table_define([pgoto], [b4_pgoto])[;
 
   /* YYDEFGOTO[NTERM-NUM].  */
-  const ]b4_int_type_for([b4_defgoto])[
-  ]b4_parser_class_name[::yydefgoto_[] =
-  {
-    ]b4_defgoto[
-  };
+  ]b4_table_define([defgoto], [b4_defgoto])[;
 
   /* YYTABLE[YYPACT[STATE-NUM]].  What to do in state STATE-NUM.  If
      positive, shift that token.  If negative, reduce the rule which
      number is the opposite.  If zero, do what YYDEFACT says.  */
   const ]b4_int_type(b4_table_ninf, b4_table_ninf) b4_parser_class_name::yytable_ninf_ = b4_table_ninf[;
-  const ]b4_int_type_for([b4_table])[
-  ]b4_parser_class_name[::yytable_[] =
-  {
-    ]b4_table[
-  };
+  ]b4_table_define([table], [b4_table])[;
 
   /* YYCHECK.  */
-  const ]b4_int_type_for([b4_check])[
-  ]b4_parser_class_name[::yycheck_[] =
-  {
-    ]b4_check[
-  };
+  ]b4_table_define([check], [b4_check])[;
 
   /* STOS_[STATE-NUM] -- The (internal number of the) accessing
      symbol of state STATE-NUM.  */
-  const ]b4_int_type_for([b4_stos])[
-  ]b4_parser_class_name[::yystos_[] =
-  {
-    ]b4_stos[
-  };
-
-#if YYDEBUG
-  /* TOKEN_NUMBER_[YYLEX-NUM] -- Internal symbol number corresponding
-     to YYLEX-NUM.  */
-  const ]b4_int_type_for([b4_toknum])[
-  ]b4_parser_class_name[::yytoken_number_[] =
-  {
-    ]b4_toknum[
-  };
-#endif
+  ]b4_table_define([stos], [b4_stos])[;
 
   /* YYR1[YYN] -- Symbol number of symbol that rule YYN derives.  */
-  const ]b4_int_type_for([b4_r1])[
-  ]b4_parser_class_name[::yyr1_[] =
-  {
-    ]b4_r1[
-  };
+  ]b4_table_define([r1], [b4_r1])[;
 
   /* YYR2[YYN] -- Number of symbols composing right hand side of rule YYN.  */
-  const ]b4_int_type_for([b4_r2])[
-  ]b4_parser_class_name[::yyr2_[] =
-  {
-    ]b4_r2[
-  };
+  ]b4_table_define([r2], [b4_r2])[;
 
 #if YYDEBUG || YYERROR_VERBOSE || YYTOKEN_TABLE
   /* YYTNAME[SYMBOL-NUM] -- String name of the symbol SYMBOL-NUM.
@@ -964,41 +1583,24 @@ b4_error_verbose_if([, int tok])[)
   const char*
   const ]b4_parser_class_name[::yytname_[] =
   {
-    ]b4_tname[
+  ]b4_tname[
   };
 #endif
 
 #if YYDEBUG
-  /* YYRHS -- A `-1'-separated list of the rules' RHS.  */
-  const ]b4_parser_class_name[::rhs_number_type
-  ]b4_parser_class_name[::yyrhs_[] =
-  {
-    ]b4_rhs[
-  };
-
-  /* YYPRHS[YYN] -- Index of the first RHS symbol of rule number YYN in
-     YYRHS.  */
-  const ]b4_int_type_for([b4_prhs])[
-  ]b4_parser_class_name[::yyprhs_[] =
-  {
-    ]b4_prhs[
-  };
-
   /* YYRLINE[YYN] -- Source line where rule number YYN was defined.  */
-  const ]b4_int_type_for([b4_rline])[
-  ]b4_parser_class_name[::yyrline_[] =
-  {
-    ]b4_rline[
-  };
+  ]b4_table_define([rline], [b4_rline])[;
 
   // Print the state stack on the debug stream.
   void
   ]b4_parser_class_name[::yystack_print_ ()
   {
     *yycdebug_ << "Stack now";
-    for (state_stack_type::const_iterator i = yystate_stack_.begin ();
-        i != yystate_stack_.end (); ++i)
-      *yycdebug_ << ' ' << *i;
+    for (stack_type::const_iterator
+           i = yystack_.begin (),
+           i_end = yystack_.end ();
+        i != i_end; ++i)
+      *yycdebug_ << ' ' << i->state;
     *yycdebug_ << std::endl;
   }
 
@@ -1010,59 +1612,27 @@ b4_error_verbose_if([, int tok])[)
     int yynrhs = yyr2_[yyrule];
     /* Print the symbols being reduced, and their result.  */
     *yycdebug_ << "Reducing stack by rule " << yyrule - 1
-              << " (line " << yylno << "), ";
+              << " (line " << yylno << "):" << std::endl;
     /* The symbols being reduced.  */
     for (int yyi = 0; yyi < yynrhs; yyi++)
       YY_SYMBOL_PRINT ("   $" << yyi + 1 << " =",
-                      yyrhs_[yyprhs_[yyrule] + yyi],
-                      &]b4_rhs_value(yynrhs, yyi + 1)[,
-                      &]b4_rhs_location(yynrhs, yyi + 1)[);
+                       ]b4_rhs_data(yynrhs, yyi + 1)[);
   }
 #endif // YYDEBUG
 
-  /* YYTRANSLATE(YYLEX) -- Bison symbol number corresponding to YYLEX.  */
-  ]b4_parser_class_name[::token_number_type
-  ]b4_parser_class_name[::yytranslate_ (int t)
-  {
-    static
-    const token_number_type
-    translate_table[] =
-    {
-      ]b4_translate[
-    };
-    if ((unsigned int) t <= yyuser_token_number_max_)
-      return translate_table[t];
-    else
-      return yyundef_token_;
-  }
+]b4_lex_symbol_if([], [b4_yytranslate_definition])[
+]b4_namespace_close[
 
-  const int ]b4_parser_class_name[::yyeof_ = 0;
-  const int ]b4_parser_class_name[::yylast_ = ]b4_last[;
-  const int ]b4_parser_class_name[::yynnts_ = ]b4_nterms_number[;
-  const int ]b4_parser_class_name[::yyempty_ = -2;
-  const int ]b4_parser_class_name[::yyfinal_ = ]b4_final_state_number[;
-  const int ]b4_parser_class_name[::yyterror_ = 1;
-  const int ]b4_parser_class_name[::yyerrcode_ = 256;
-  const int ]b4_parser_class_name[::yyntokens_ = ]b4_tokens_number[;
-
-  const unsigned int ]b4_parser_class_name[::yyuser_token_number_max_ = ]b4_user_token_number_max[;
-  const ]b4_parser_class_name[::token_number_type ]b4_parser_class_name[::yyundef_token_ = ]b4_undef_token_number[;
-
-} // namespace ]b4_namespace[
-
-]b4_epilogue
-dnl
-@output b4_dir_prefix[]stack.hh
-b4_copyright([Stack handling for Bison parsers in C++],
-  [2002, 2003, 2004, 2005, 2006])[
+]b4_epilogue[]dnl
+@output(b4_dir_prefix[]stack.hh@)@
+b4_copyright([Stack handling for Bison parsers in C++])[
 
 #ifndef BISON_STACK_HH
 # define BISON_STACK_HH
 
 #include <deque>
 
-namespace ]b4_namespace[
-{
+]b4_namespace_open[
   template <class T, class S = std::deque<T> >
   class stack
   {
@@ -1110,17 +1680,17 @@ namespace ]b4_namespace[
     }
 
     inline
-    unsigned int
-    height () const
+    typename S::size_type
+    size () const
     {
       return seq_.size ();
     }
 
     inline const_iterator begin () const { return seq_.rbegin (); }
-    inline const_iterator end () const { return seq_.rend (); }
+    inline const_iterator end ()   const { return seq_.rend ();   }
 
   private:
-
+    /// The wrapped container.
     S seq_;
   };
 
@@ -1148,7 +1718,9 @@ namespace ]b4_namespace[
     const S& stack_;
     unsigned int range_;
   };
-}
+]b4_namespace_close[
 
-#endif // not BISON_STACK_HH]
-m4_divert(-1)
+#endif // not BISON_STACK_HH[]dnl
+]
+m4_divert_pop(0)
+m4_popdef([b4_copyright_years])dnl