[bison.git] / data / lalr1.cc

# C++ skeleton for Bison

# 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
# it under the terms of the GNU General Public License as published by
# 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, see <http://www.gnu.org/licenses/>.

m4_include(b4_pkgdatadir/[c++.m4])

# 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([],
              [b4_fatal([b4_skeleton[: using %%defines is mandatory]])])

b4_locations_if(
[# Backward compatibility.
m4_define([b4_location_constructors])
m4_include(b4_pkgdatadir/[location.cc])])

# We do want M4 expansion after # for CPP macros.
m4_changecom()
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.  */

#ifndef PARSER_HEADER_H
# define PARSER_HEADER_H

]b4_percent_code_get([[requires]])[

]b4_assert_if([#include <cassert>])[
#include <string>
#include <iostream>
#include "stack.hh"

]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>();
    }

    /// 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
# define YYDEBUG ]b4_debug_flag[
#endif

/* Enabling verbose error messages.  */
#ifdef YYERROR_VERBOSE
# undef YYERROR_VERBOSE
# define YYERROR_VERBOSE 1
#else
# define YYERROR_VERBOSE ]b4_error_verbose_flag[
#endif

/* Enabling the token table.  */
#ifndef YYTOKEN_TABLE
# define YYTOKEN_TABLE ]b4_token_table[
#endif

]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].location.begin;                \
      (Current).end   = (Rhs)[N].location.end;                  \
    }                                                           \
  else                                                          \
    {                                                           \
      (Current).begin = (Current).end = (Rhs)[0].location.end;  \
    }                                                           \
} while (false)
#endif]])[

]b4_namespace_open[

  /// A Bison parser.
  class ]b4_parser_class_name[
  {
  public:
#ifndef YYSTYPE
]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
    };],
[m4_if(b4_tag_seen_flag, 0,
[[    typedef int semantic_type;]],
[[    typedef YYSTYPE semantic_type;]])])])[
#else
    typedef YYSTYPE semantic_type;
#endif]b4_locations_if([
    /// Symbol locations.
    typedef b4_percent_define_get([[location_type]]) location_type;])[
    /// Tokens.
    struct token
    {
      ]b4_token_enums(b4_tokens)[
    };
    /// Token type.
    typedef token::yytokentype token_type;

    /// Build a parser object.
    ]b4_parser_class_name[ (]b4_parse_param_decl[);
    virtual ~]b4_parser_class_name[ ();

    /// Parse.
    /// \returns  0 iff parsing succeeded.
    virtual int parse ();

#if YYDEBUG
    /// The current debugging stream.
    std::ostream& debug_stream () const;
    /// Set the current debugging stream.
    void set_debug_stream (std::ostream &);

    /// Type for debugging levels.
    typedef int debug_level_type;
    /// The current debugging level.
    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.]b4_locations_if([
    /// \param loc    where the syntax error is found.])[
    /// \param msg    a description of the syntax error.
    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, int tok);

    /// State numbers.
    typedef int state_type;

    /// Internal symbol numbers.
    typedef ]b4_int_type_for([b4_translate])[ token_number_type;
    /* Tables.  */
    /// For a state, the index in \a yytable_ of its portion.
    static const ]b4_int_type_for([b4_pact])[ yypact_[];
    static const ]b4_int_type(b4_pact_ninf, b4_pact_ninf)[ yypact_ninf_;

    /// For a state, default rule to reduce.
    /// Unless\a  yytable_ specifies something else to do.
    /// Zero means the default is an error.
    static const ]b4_int_type_for([b4_defact])[ yydefact_[];

    static const ]b4_int_type_for([b4_pgoto])[ yypgoto_[];
    static const ]b4_int_type_for([b4_defgoto])[ yydefgoto_[];

    /// What to do in a state.
    /// \a yytable_[yypact_[s]]: what to do in state \a s.
    /// - if positive, shift that token.
    /// - if negative, reduce the rule which number is the opposite.
    /// - if zero, do what YYDEFACT says.
    static const ]b4_int_type_for([b4_table])[ yytable_[];
    static const ]b4_int_type(b4_table_ninf, b4_table_ninf)[ yytable_ninf_;

    static const ]b4_int_type_for([b4_check])[ yycheck_[];

    /// For a state, its accessing symbol.
    static const ]b4_int_type_for([b4_stos])[ yystos_[];

    /// For a rule, its LHS.
    static const ]b4_int_type_for([b4_r1])[ yyr1_[];
    /// For a rule, its RHS length.
    static const ]b4_int_type_for([b4_r2])[ yyr2_[];

#if YYDEBUG || YYERROR_VERBOSE || YYTOKEN_TABLE
    /// For a symbol, its name in clear.
    static const char* const yytname_[];
#endif]b4_error_verbose_if([

    /// Convert the symbol name \a n to a form suitable for a diagnostic.
    static std::string yytnamerr_ (const char *n);])[

#if YYDEBUG
    /// For each rule, its source line number.
    static const ]b4_int_type_for([b4_rline])[ yyrline_[];
    /// 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.
    virtual void yystack_print_ ();

    /* Debugging.  */
    int yydebug_;
    std::ostream* yycdebug_;
#endif

    /// Convert a scanner token number \a t to a symbol number.
    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.
    ///                  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.  */
    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[
  };

]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_ref::b4_parser_class_name::semantic_type
#endif
])
b4_percent_code_get([[provides]])[]dnl

[#endif /* ! defined PARSER_HEADER_H */]
@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_user_pre_prologue[

#include "@basename(]b4_spec_defines_file[@)"

/* User implementation prologue.  */
]b4_user_post_prologue
b4_percent_code_get[]dnl

[#ifndef YY_
# if YYENABLE_NLS
#  if ENABLE_NLS
#   include <libintl.h> /* FIXME: INFRINGES ON USER NAME SPACE */
#   define YY_(msgid) dgettext ("bison-runtime", msgid)
#  endif
# endif
# ifndef YY_
#  define YY_(msgid) msgid
# endif
#endif

/* Suppress unused-variable warnings by "using" E.  */
#define YYUSE(e) ((void) (e))

/* Enable debugging if requested.  */
#if YYDEBUG

/* A pseudo ostream that takes yydebug_ into account.  */
# define YYCDEBUG if (yydebug_) (*yycdebug_)

# 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)

# define YY_STACK_PRINT()               \
  do {                                  \
    if (yydebug_)                       \
      yystack_print_ ();                \
  } while (false)

#else /* !YYDEBUG */

# define YYCDEBUG if (false) std::cerr
# 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 yyerrok         (yyerrstatus_ = 0)
#define yyclearin       (yyempty = true)

#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
     that double-quoting is unnecessary unless the string contains an
     apostrophe, a comma, or backslash (other than backslash-backslash).
     YYSTR is taken from yytname.  */
  std::string
  ]b4_parser_class_name[::yytnamerr_ (const char *yystr)
  {
    if (*yystr == '"')
      {
        std::string yyr = "";
        char const *yyp = yystr;

        for (;;)
          switch (*++yyp)
            {
            case '\'':
            case ',':
              goto do_not_strip_quotes;

            case '\\':
              if (*++yyp != '\\')
                goto do_not_strip_quotes;
              /* Fall through.  */
            default:
              yyr += *yyp;
              break;

            case '"':
              return yyr;
            }
      do_not_strip_quotes: ;
      }

    return yystr;
  }
]])[

  /// Build a parser object.
  ]b4_parser_class_name::b4_parser_class_name[ (]b4_parse_param_decl[)]m4_ifset([b4_parse_param], [
    :])[
#if YYDEBUG
    ]m4_ifset([b4_parse_param], [  ], [ :])[yydebug_ (false),
      yycdebug_ (&std::cerr)]m4_ifset([b4_parse_param], [,])[
#endif]b4_parse_param_cons[
  {
  }

  ]b4_parser_class_name::~b4_parser_class_name[ ()
  {
  }


  /*---------------.
  | 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 ()
  {
  }

  ]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)
  {
  }

  int
  ]b4_parser_class_name[::stack_symbol_type::type_get_ () const
  {
    return yystos_[state];
  }


  template <typename Exact>
  void
  ]b4_parser_class_name[::yy_destroy_ (const char* yymsg,
                                       symbol_base_type<Exact>& yysym) const
  {
    int yytype = yysym.type_get ();
    YYUSE (yymsg);
    if (yymsg)
      YY_SYMBOL_PRINT (yymsg, yysym);

    // User destructor.
    switch (yytype)
      {
]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)
  {
    yystack_.pop (n);
  }

#if YYDEBUG
  std::ostream&
  ]b4_parser_class_name[::debug_stream () const
  {
    return *yycdebug_;
  }

  void
  ]b4_parser_class_name[::set_debug_stream (std::ostream& o)
  {
    yycdebug_ = &o;
  }


  ]b4_parser_class_name[::debug_level_type
  ]b4_parser_class_name[::debug_level () const
  {
    return yydebug_;
  }

  void
  ]b4_parser_class_name[::set_debug_level (debug_level_type l)
  {
    yydebug_ = l;
  }
#endif

  int
  ]b4_parser_class_name[::parse ()
  {
    /// Whether yyla contains a lookahead.
    bool yyempty = true;

    /* State.  */
    int yyn;
    int yylen = 0;
    int yystate = 0;

    /* Error handling.  */
    int yynerrs_ = 0;
    int yyerrstatus_ = 0;

    /// The lookahead symbol.
    symbol_type yyla;]b4_locations_if([[

    /// The locations where the error started and ended.
    stack_symbol_type yyerror_range[2];]])[

    /// $$ 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],     [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 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.  */
    yystack_ = stack_type (0);
    yypush_ (0, 0, yyla);

    // A new state was pushed on the stack.
    // Invariant: yystate == yystack_[0].state, i.e.,
    // yystate was just pushed onto the state stack.
  yynewstate:
    YYCDEBUG << "Entering state " << yystate << std::endl;

    /* Accept?  */
    if (yystate == yyfinal_)
      goto yyacceptlab;

    goto yybackup;

    /* Backup.  */
  yybackup:

    /* Try to take a decision without lookahead.  */
    yyn = yypact_[yystate];
    if (yyn == yypact_ninf_)
      goto yydefault;

    /* Read a lookahead token.  */
    if (yyempty)
      {
        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 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.  */
    yyn = yytable_[yyn];
    if (yyn <= 0)
      {
        if (yyn == 0 || yyn == yytable_ninf_)
          goto yyerrlab;
        yyn = -yyn;
        goto yyreduce;
      }

    /* Discard the token being shifted.  */
    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;

  /*-----------------------------------------------------------.
  | yydefault -- do the default action for the current state.  |
  `-----------------------------------------------------------*/
  yydefault:
    yyn = yydefact_[yystate];
    if (yyn == 0)
      goto yyerrlab;
    goto yyreduce;

  /*-----------------------------.
  | yyreduce -- Do a reduction.  |
  `-----------------------------*/
  yyreduce:
    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 YYLHS.VALUE to garbage.
       This behavior is undocumented and Bison
       users should not rely upon it.  */
    if (yylen)
      yylhs.value = yystack_@{yylen - 1@}.value;
    else
      yylhs.value = yystack_@{0@}.value;])[
]b4_locations_if([dnl
[
    // Compute the default @@$.
    {
      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;
      }
    // 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 ();

    /* Shift the result of the reduction.  */
    yypush_ (0, yylhs);
    goto yynewstate;

  /*------------------------------------.
  | yyerrlab -- here on detecting error |
  `------------------------------------*/
  yyerrlab:
    /* If not already recovering from an error, report this error.  */
    if (!yyerrstatus_)
      {
        ++yynerrs_;
        error (]b4_args(b4_locations_if([yyla.location]),
                        [yysyntax_error_ (yystate, yyla.type)])[);
      }

]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.  */

        /* Return failure if at end of input.  */
        if (yyla.type == yyeof_)
          YYABORT;
        else
          {
            yy_destroy_ ("Error: discarding", yyla);
            yyempty = true;
          }
      }

    /* Else will try to reuse lookahead token after shifting the error
       token.  */
    goto yyerrlab1;


  /*---------------------------------------------------.
  | yyerrorlab -- error raised explicitly by YYERROR.  |
  `---------------------------------------------------*/
  yyerrorlab:

    /* Pacify compilers like GCC when the user code never invokes
       YYERROR and the label yyerrorlab therefore never appears in user
       code.  */
    if (false)
      goto yyerrorlab;

]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 = yystack_[0].state;
    goto yyerrlab1;

  /*-------------------------------------------------------------.
  | yyerrlab1 -- common code for both syntax error and YYERROR.  |
  `-------------------------------------------------------------*/
  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;
                }
            }

          // 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.  */
  yyacceptlab:
    yyresult = 0;
    goto yyreturn;

    /* Abort.  */
  yyabortlab:
    yyresult = 1;
    goto yyreturn;

  yyreturn:
    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 (yystack_.size () != 1)
      {
        yy_destroy_ ("Cleanup: popping", yystack_[0]);
        yypop_ ();
      }

    return yyresult;
  }

  // Generate an error message.
  std::string
  ]b4_parser_class_name[::yysyntax_error_ (]dnl
b4_error_verbose_if([int yystate, int yytoken],
                    [int, int])[)
  {
    std::string yyres;]b4_error_verbose_if([[
    int yyn = yypact_[yystate];
    if (yypact_ninf_ < yyn && yyn <= yylast_)
      {
        /* Start YYX at -YYN if negative to avoid negative indexes in
           YYCHECK.  */
        int yyxbegin = yyn < 0 ? -yyn : 0;

        /* Stay within bounds of both yycheck and yytname.  */
        int yychecklim = yylast_ - yyn + 1;
        int yyxend = yychecklim < yyntokens_ ? yychecklim : yyntokens_;

        // 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
  ]])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[;
  ]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.  */
  ]b4_table_define([defact], [b4_defact])[;

  /* YYPGOTO[NTERM-NUM].  */
  ]b4_table_define([pgoto], [b4_pgoto])[;

  /* YYDEFGOTO[NTERM-NUM].  */
  ]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[;
  ]b4_table_define([table], [b4_table])[;

  /* YYCHECK.  */
  ]b4_table_define([check], [b4_check])[;

  /* STOS_[STATE-NUM] -- The (internal number of the) accessing
     symbol of state STATE-NUM.  */
  ]b4_table_define([stos], [b4_stos])[;

  /* YYR1[YYN] -- Symbol number of symbol that rule YYN derives.  */
  ]b4_table_define([r1], [b4_r1])[;

  /* YYR2[YYN] -- Number of symbols composing right hand side of rule YYN.  */
  ]b4_table_define([r2], [b4_r2])[;

#if YYDEBUG || YYERROR_VERBOSE || YYTOKEN_TABLE
  /* YYTNAME[SYMBOL-NUM] -- String name of the symbol SYMBOL-NUM.
     First, the terminals, then, starting at \a yyntokens_, nonterminals.  */
  const char*
  const ]b4_parser_class_name[::yytname_[] =
  {
  ]b4_tname[
  };
#endif

#if YYDEBUG
  /* YYRLINE[YYN] -- Source line where rule number YYN was defined.  */
  ]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 (stack_type::const_iterator
           i = yystack_.begin (),
           i_end = yystack_.end ();
         i != i_end; ++i)
      *yycdebug_ << ' ' << i->state;
    *yycdebug_ << std::endl;
  }

  // Report on the debug stream that the rule \a yyrule is going to be reduced.
  void
  ]b4_parser_class_name[::yy_reduce_print_ (int yyrule)
  {
    unsigned int yylno = yyrline_[yyrule];
    int yynrhs = yyr2_[yyrule];
    /* Print the symbols being reduced, and their result.  */
    *yycdebug_ << "Reducing stack by rule " << yyrule - 1
               << " (line " << yylno << "):" << std::endl;
    /* The symbols being reduced.  */
    for (int yyi = 0; yyi < yynrhs; yyi++)
      YY_SYMBOL_PRINT ("   $" << yyi + 1 << " =",
                       ]b4_rhs_data(yynrhs, yyi + 1)[);
  }
#endif // YYDEBUG

]b4_lex_symbol_if([], [b4_yytranslate_definition])[
]b4_namespace_close[

]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>

]b4_namespace_open[
  template <class T, class S = std::deque<T> >
  class stack
  {
  public:

    // Hide our reversed order.
    typedef typename S::reverse_iterator iterator;
    typedef typename S::const_reverse_iterator const_iterator;

    stack () : seq_ ()
    {
    }

    stack (unsigned int n) : seq_ (n)
    {
    }

    inline
    T&
    operator [] (unsigned int i)
    {
      return seq_[i];
    }

    inline
    const T&
    operator [] (unsigned int i) const
    {
      return seq_[i];
    }

    inline
    void
    push (const T& t)
    {
      seq_.push_front (t);
    }

    inline
    void
    pop (unsigned int n = 1)
    {
      for (; n; --n)
        seq_.pop_front ();
    }

    inline
    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 ();   }

  private:
    /// The wrapped container.
    S seq_;
  };

  /// Present a slice of the top of a stack.
  template <class T, class S = stack<T> >
  class slice
  {
  public:

    slice (const S& stack,
           unsigned int range) : stack_ (stack),
                                 range_ (range)
    {
    }

    inline
    const T&
    operator [] (unsigned int i) const
    {
      return stack_[range_ - i];
    }

  private:

    const S& stack_;
    unsigned int range_;
  };
]b4_namespace_close[

#endif // not BISON_STACK_HH[]dnl
]
m4_divert_pop(0)
m4_popdef([b4_copyright_years])dnl