+@noindent
+Tuning the parser:
+
+@table @option
+@item -t
+@itemx --debug
+In the parser file, define the macro @code{YYDEBUG} to 1 if it is not
+already defined, so that the debugging facilities are compiled.
+@xref{Tracing, ,Tracing Your Parser}.
+
+@item -D @var{name}[=@var{value}]
+@itemx --define=@var{name}[=@var{value}]
+Same as running @samp{%define @var{name} "@var{value}"} (@pxref{Decl
+Summary, ,%define}).
+
+@item -L @var{language}
+@itemx --language=@var{language}
+Specify the programming language for the generated parser, as if
+@code{%language} was specified (@pxref{Decl Summary, , Bison Declaration
+Summary}). Currently supported languages include C, C++, and Java.
+@var{language} is case-insensitive.
+
+This option is experimental and its effect may be modified in future
+releases.
+
+@item --locations
+Pretend that @code{%locations} was specified. @xref{Decl Summary}.
+
+@item -p @var{prefix}
+@itemx --name-prefix=@var{prefix}
+Pretend that @code{%name-prefix "@var{prefix}"} was specified.
+@xref{Decl Summary}.
+
+@item -l
+@itemx --no-lines
+Don't put any @code{#line} preprocessor commands in the parser file.
+Ordinarily Bison puts them in the parser file so that the C compiler
+and debuggers will associate errors with your source file, the
+grammar file. This option causes them to associate errors with the
+parser file, treating it as an independent source file in its own right.
+
+@item -S @var{file}
+@itemx --skeleton=@var{file}
+Specify the skeleton to use, similar to @code{%skeleton}
+(@pxref{Decl Summary, , Bison Declaration Summary}).
+
+@c You probably don't need this option unless you are developing Bison.
+@c You should use @option{--language} if you want to specify the skeleton for a
+@c different language, because it is clearer and because it will always
+@c choose the correct skeleton for non-deterministic or push parsers.
+
+If @var{file} does not contain a @code{/}, @var{file} is the name of a skeleton
+file in the Bison installation directory.
+If it does, @var{file} is an absolute file name or a file name relative to the
+current working directory.
+This is similar to how most shells resolve commands.
+
+@item -k
+@itemx --token-table
+Pretend that @code{%token-table} was specified. @xref{Decl Summary}.
+@end table
+
+@noindent
+Adjust the output:
+
+@table @option
+@item --defines[=@var{file}]
+Pretend that @code{%defines} was specified, i.e., write an extra output
+file containing macro definitions for the token type names defined in
+the grammar, as well as a few other declarations. @xref{Decl Summary}.
+
+@item -d
+This is the same as @code{--defines} except @code{-d} does not accept a
+@var{file} argument since POSIX Yacc requires that @code{-d} can be bundled
+with other short options.
+
+@item -b @var{file-prefix}
+@itemx --file-prefix=@var{prefix}
+Pretend that @code{%file-prefix} was specified, i.e., specify prefix to use
+for all Bison output file names. @xref{Decl Summary}.
+
+@item -r @var{things}
+@itemx --report=@var{things}
+Write an extra output file containing verbose description of the comma
+separated list of @var{things} among:
+
+@table @code
+@item state
+Description of the grammar, conflicts (resolved and unresolved), and
+@acronym{LALR} automaton.
+
+@item lookahead
+Implies @code{state} and augments the description of the automaton with
+each rule's lookahead set.
+
+@item itemset
+Implies @code{state} and augments the description of the automaton with
+the full set of items for each state, instead of its core only.
+@end table
+
+@item --report-file=@var{file}
+Specify the @var{file} for the verbose description.
+
+@item -v
+@itemx --verbose
+Pretend that @code{%verbose} was specified, i.e., write an extra output
+file containing verbose descriptions of the grammar and
+parser. @xref{Decl Summary}.
+
+@item -o @var{file}
+@itemx --output=@var{file}
+Specify the @var{file} for the parser file.
+
+The other output files' names are constructed from @var{file} as
+described under the @samp{-v} and @samp{-d} options.
+
+@item -g [@var{file}]
+@itemx --graph[=@var{file}]
+Output a graphical representation of the @acronym{LALR}(1) grammar
+automaton computed by Bison, in @uref{http://www.graphviz.org/, Graphviz}
+@uref{http://www.graphviz.org/doc/info/lang.html, @acronym{DOT}} format.
+@code{@var{file}} is optional.
+If omitted and the grammar file is @file{foo.y}, the output file will be
+@file{foo.dot}.
+
+@item -x [@var{file}]
+@itemx --xml[=@var{file}]
+Output an XML report of the @acronym{LALR}(1) automaton computed by Bison.
+@code{@var{file}} is optional.
+If omitted and the grammar file is @file{foo.y}, the output file will be
+@file{foo.xml}.
+(The current XML schema is experimental and may evolve.
+More user feedback will help to stabilize it.)
+@end table
+
+@node Option Cross Key
+@section Option Cross Key
+
+Here is a list of options, alphabetized by long option, to help you find
+the corresponding short option.
+
+@multitable {@option{--defines=@var{defines-file}}} {@option{-D @var{name}[=@var{value}]}} {@code{%nondeterministic-parser}}
+@headitem Long Option @tab Short Option @tab Bison Directive
+@include cross-options.texi
+@end multitable
+
+@node Yacc Library
+@section Yacc Library
+
+The Yacc library contains default implementations of the
+@code{yyerror} and @code{main} functions. These default
+implementations are normally not useful, but @acronym{POSIX} requires
+them. To use the Yacc library, link your program with the
+@option{-ly} option. Note that Bison's implementation of the Yacc
+library is distributed under the terms of the @acronym{GNU} General
+Public License (@pxref{Copying}).
+
+If you use the Yacc library's @code{yyerror} function, you should
+declare @code{yyerror} as follows:
+
+@example
+int yyerror (char const *);
+@end example
+
+Bison ignores the @code{int} value returned by this @code{yyerror}.
+If you use the Yacc library's @code{main} function, your
+@code{yyparse} function should have the following type signature:
+
+@example
+int yyparse (void);
+@end example
+
+@c ================================================= C++ Bison
+
+@node Other Languages
+@chapter Parsers Written In Other Languages
+
+@menu
+* C++ Parsers:: The interface to generate C++ parser classes
+* Java Parsers:: The interface to generate Java parser classes
+@end menu
+
+@node C++ Parsers
+@section C++ Parsers
+
+@menu
+* C++ Bison Interface:: Asking for C++ parser generation
+* C++ Semantic Values:: %union vs. C++
+* C++ Location Values:: The position and location classes
+* C++ Parser Interface:: Instantiating and running the parser
+* C++ Scanner Interface:: Exchanges between yylex and parse
+* A Complete C++ Example:: Demonstrating their use
+@end menu
+
+@node C++ Bison Interface
+@subsection C++ Bison Interface
+@c - %skeleton "lalr1.cc"
+@c - Always pure
+@c - initial action
+
+The C++ @acronym{LALR}(1) parser is selected using the skeleton directive,
+@samp{%skeleton "lalr1.c"}, or the synonymous command-line option
+@option{--skeleton=lalr1.c}.
+@xref{Decl Summary}.
+
+When run, @command{bison} will create several entities in the @samp{yy}
+namespace.
+@findex %define namespace
+Use the @samp{%define namespace} directive to change the namespace name, see
+@ref{Decl Summary}.
+The various classes are generated in the following files:
+
+@table @file
+@item position.hh
+@itemx location.hh
+The definition of the classes @code{position} and @code{location},
+used for location tracking. @xref{C++ Location Values}.
+
+@item stack.hh
+An auxiliary class @code{stack} used by the parser.
+
+@item @var{file}.hh
+@itemx @var{file}.cc
+(Assuming the extension of the input file was @samp{.yy}.) The
+declaration and implementation of the C++ parser class. The basename
+and extension of these two files follow the same rules as with regular C
+parsers (@pxref{Invocation}).
+
+The header is @emph{mandatory}; you must either pass
+@option{-d}/@option{--defines} to @command{bison}, or use the
+@samp{%defines} directive.
+@end table
+
+All these files are documented using Doxygen; run @command{doxygen}
+for a complete and accurate documentation.
+
+@node C++ Semantic Values
+@subsection C++ Semantic Values
+@c - No objects in unions
+@c - YYSTYPE
+@c - Printer and destructor
+
+The @code{%union} directive works as for C, see @ref{Union Decl, ,The
+Collection of Value Types}. In particular it produces a genuine
+@code{union}@footnote{In the future techniques to allow complex types
+within pseudo-unions (similar to Boost variants) might be implemented to
+alleviate these issues.}, which have a few specific features in C++.
+@itemize @minus
+@item
+The type @code{YYSTYPE} is defined but its use is discouraged: rather
+you should refer to the parser's encapsulated type
+@code{yy::parser::semantic_type}.
+@item
+Non POD (Plain Old Data) types cannot be used. C++ forbids any
+instance of classes with constructors in unions: only @emph{pointers}
+to such objects are allowed.
+@end itemize
+
+Because objects have to be stored via pointers, memory is not
+reclaimed automatically: using the @code{%destructor} directive is the
+only means to avoid leaks. @xref{Destructor Decl, , Freeing Discarded
+Symbols}.
+
+
+@node C++ Location Values
+@subsection C++ Location Values
+@c - %locations
+@c - class Position
+@c - class Location
+@c - %define filename_type "const symbol::Symbol"
+
+When the directive @code{%locations} is used, the C++ parser supports
+location tracking, see @ref{Locations, , Locations Overview}. Two
+auxiliary classes define a @code{position}, a single point in a file,
+and a @code{location}, a range composed of a pair of
+@code{position}s (possibly spanning several files).
+
+@deftypemethod {position} {std::string*} file
+The name of the file. It will always be handled as a pointer, the
+parser will never duplicate nor deallocate it. As an experimental
+feature you may change it to @samp{@var{type}*} using @samp{%define
+filename_type "@var{type}"}.
+@end deftypemethod
+
+@deftypemethod {position} {unsigned int} line
+The line, starting at 1.
+@end deftypemethod
+
+@deftypemethod {position} {unsigned int} lines (int @var{height} = 1)
+Advance by @var{height} lines, resetting the column number.
+@end deftypemethod
+
+@deftypemethod {position} {unsigned int} column
+The column, starting at 0.
+@end deftypemethod
+
+@deftypemethod {position} {unsigned int} columns (int @var{width} = 1)
+Advance by @var{width} columns, without changing the line number.
+@end deftypemethod
+
+@deftypemethod {position} {position&} operator+= (position& @var{pos}, int @var{width})
+@deftypemethodx {position} {position} operator+ (const position& @var{pos}, int @var{width})
+@deftypemethodx {position} {position&} operator-= (const position& @var{pos}, int @var{width})
+@deftypemethodx {position} {position} operator- (position& @var{pos}, int @var{width})
+Various forms of syntactic sugar for @code{columns}.
+@end deftypemethod
+
+@deftypemethod {position} {position} operator<< (std::ostream @var{o}, const position& @var{p})
+Report @var{p} on @var{o} like this:
+@samp{@var{file}:@var{line}.@var{column}}, or
+@samp{@var{line}.@var{column}} if @var{file} is null.
+@end deftypemethod
+
+@deftypemethod {location} {position} begin
+@deftypemethodx {location} {position} end
+The first, inclusive, position of the range, and the first beyond.
+@end deftypemethod
+
+@deftypemethod {location} {unsigned int} columns (int @var{width} = 1)
+@deftypemethodx {location} {unsigned int} lines (int @var{height} = 1)
+Advance the @code{end} position.
+@end deftypemethod
+
+@deftypemethod {location} {location} operator+ (const location& @var{begin}, const location& @var{end})
+@deftypemethodx {location} {location} operator+ (const location& @var{begin}, int @var{width})
+@deftypemethodx {location} {location} operator+= (const location& @var{loc}, int @var{width})
+Various forms of syntactic sugar.
+@end deftypemethod
+
+@deftypemethod {location} {void} step ()
+Move @code{begin} onto @code{end}.
+@end deftypemethod
+
+
+@node C++ Parser Interface
+@subsection C++ Parser Interface
+@c - define parser_class_name
+@c - Ctor
+@c - parse, error, set_debug_level, debug_level, set_debug_stream,
+@c debug_stream.
+@c - Reporting errors
+
+The output files @file{@var{output}.hh} and @file{@var{output}.cc}
+declare and define the parser class in the namespace @code{yy}. The
+class name defaults to @code{parser}, but may be changed using
+@samp{%define parser_class_name "@var{name}"}. The interface of
+this class is detailed below. It can be extended using the
+@code{%parse-param} feature: its semantics is slightly changed since
+it describes an additional member of the parser class, and an
+additional argument for its constructor.
+
+@defcv {Type} {parser} {semantic_value_type}
+@defcvx {Type} {parser} {location_value_type}
+The types for semantics value and locations.
+@end defcv
+
+@deftypemethod {parser} {} parser (@var{type1} @var{arg1}, ...)
+Build a new parser object. There are no arguments by default, unless
+@samp{%parse-param @{@var{type1} @var{arg1}@}} was used.
+@end deftypemethod
+
+@deftypemethod {parser} {int} parse ()
+Run the syntactic analysis, and return 0 on success, 1 otherwise.
+@end deftypemethod
+
+@deftypemethod {parser} {std::ostream&} debug_stream ()
+@deftypemethodx {parser} {void} set_debug_stream (std::ostream& @var{o})
+Get or set the stream used for tracing the parsing. It defaults to
+@code{std::cerr}.
+@end deftypemethod
+
+@deftypemethod {parser} {debug_level_type} debug_level ()
+@deftypemethodx {parser} {void} set_debug_level (debug_level @var{l})
+Get or set the tracing level. Currently its value is either 0, no trace,
+or nonzero, full tracing.
+@end deftypemethod
+
+@deftypemethod {parser} {void} error (const location_type& @var{l}, const std::string& @var{m})
+The definition for this member function must be supplied by the user:
+the parser uses it to report a parser error occurring at @var{l},
+described by @var{m}.
+@end deftypemethod
+
+
+@node C++ Scanner Interface
+@subsection C++ Scanner Interface
+@c - prefix for yylex.
+@c - Pure interface to yylex
+@c - %lex-param
+
+The parser invokes the scanner by calling @code{yylex}. Contrary to C
+parsers, C++ parsers are always pure: there is no point in using the
+@code{%define api.pure} directive. Therefore the interface is as follows.
+
+@deftypemethod {parser} {int} yylex (semantic_value_type& @var{yylval}, location_type& @var{yylloc}, @var{type1} @var{arg1}, ...)
+Return the next token. Its type is the return value, its semantic
+value and location being @var{yylval} and @var{yylloc}. Invocations of
+@samp{%lex-param @{@var{type1} @var{arg1}@}} yield additional arguments.
+@end deftypemethod
+
+
+@node A Complete C++ Example
+@subsection A Complete C++ Example
+
+This section demonstrates the use of a C++ parser with a simple but
+complete example. This example should be available on your system,
+ready to compile, in the directory @dfn{../bison/examples/calc++}. It
+focuses on the use of Bison, therefore the design of the various C++
+classes is very naive: no accessors, no encapsulation of members etc.
+We will use a Lex scanner, and more precisely, a Flex scanner, to
+demonstrate the various interaction. A hand written scanner is
+actually easier to interface with.
+
+@menu
+* Calc++ --- C++ Calculator:: The specifications
+* Calc++ Parsing Driver:: An active parsing context
+* Calc++ Parser:: A parser class
+* Calc++ Scanner:: A pure C++ Flex scanner
+* Calc++ Top Level:: Conducting the band
+@end menu
+
+@node Calc++ --- C++ Calculator
+@subsubsection Calc++ --- C++ Calculator
+
+Of course the grammar is dedicated to arithmetics, a single
+expression, possibly preceded by variable assignments. An
+environment containing possibly predefined variables such as
+@code{one} and @code{two}, is exchanged with the parser. An example
+of valid input follows.
+
+@example
+three := 3
+seven := one + two * three
+seven * seven
+@end example
+
+@node Calc++ Parsing Driver
+@subsubsection Calc++ Parsing Driver
+@c - An env
+@c - A place to store error messages
+@c - A place for the result
+
+To support a pure interface with the parser (and the scanner) the
+technique of the ``parsing context'' is convenient: a structure
+containing all the data to exchange. Since, in addition to simply
+launch the parsing, there are several auxiliary tasks to execute (open
+the file for parsing, instantiate the parser etc.), we recommend
+transforming the simple parsing context structure into a fully blown
+@dfn{parsing driver} class.
+
+The declaration of this driver class, @file{calc++-driver.hh}, is as
+follows. The first part includes the CPP guard and imports the
+required standard library components, and the declaration of the parser
+class.
+
+@comment file: calc++-driver.hh
+@example
+#ifndef CALCXX_DRIVER_HH
+# define CALCXX_DRIVER_HH
+# include <string>
+# include <map>
+# include "calc++-parser.hh"
+@end example
+
+
+@noindent
+Then comes the declaration of the scanning function. Flex expects
+the signature of @code{yylex} to be defined in the macro
+@code{YY_DECL}, and the C++ parser expects it to be declared. We can
+factor both as follows.
+
+@comment file: calc++-driver.hh
+@example
+// Tell Flex the lexer's prototype ...
+# define YY_DECL \
+ yy::calcxx_parser::token_type \
+ yylex (yy::calcxx_parser::semantic_type* yylval, \
+ yy::calcxx_parser::location_type* yylloc, \
+ calcxx_driver& driver)
+// ... and declare it for the parser's sake.
+YY_DECL;
+@end example
+
+@noindent
+The @code{calcxx_driver} class is then declared with its most obvious
+members.
+
+@comment file: calc++-driver.hh
+@example
+// Conducting the whole scanning and parsing of Calc++.
+class calcxx_driver
+@{
+public:
+ calcxx_driver ();
+ virtual ~calcxx_driver ();
+
+ std::map<std::string, int> variables;
+
+ int result;
+@end example
+
+@noindent
+To encapsulate the coordination with the Flex scanner, it is useful to
+have two members function to open and close the scanning phase.
+
+@comment file: calc++-driver.hh
+@example
+ // Handling the scanner.
+ void scan_begin ();
+ void scan_end ();
+ bool trace_scanning;
+@end example
+
+@noindent
+Similarly for the parser itself.
+
+@comment file: calc++-driver.hh
+@example
+ // Run the parser. Return 0 on success.
+ int parse (const std::string& f);
+ std::string file;
+ bool trace_parsing;
+@end example
+
+@noindent
+To demonstrate pure handling of parse errors, instead of simply
+dumping them on the standard error output, we will pass them to the
+compiler driver using the following two member functions. Finally, we
+close the class declaration and CPP guard.
+
+@comment file: calc++-driver.hh
+@example
+ // Error handling.
+ void error (const yy::location& l, const std::string& m);
+ void error (const std::string& m);
+@};
+#endif // ! CALCXX_DRIVER_HH
+@end example
+
+The implementation of the driver is straightforward. The @code{parse}
+member function deserves some attention. The @code{error} functions
+are simple stubs, they should actually register the located error
+messages and set error state.
+
+@comment file: calc++-driver.cc
+@example
+#include "calc++-driver.hh"
+#include "calc++-parser.hh"
+
+calcxx_driver::calcxx_driver ()
+ : trace_scanning (false), trace_parsing (false)
+@{
+ variables["one"] = 1;
+ variables["two"] = 2;
+@}
+
+calcxx_driver::~calcxx_driver ()
+@{
+@}
+
+int
+calcxx_driver::parse (const std::string &f)
+@{
+ file = f;
+ scan_begin ();
+ yy::calcxx_parser parser (*this);
+ parser.set_debug_level (trace_parsing);
+ int res = parser.parse ();
+ scan_end ();
+ return res;
+@}
+
+void
+calcxx_driver::error (const yy::location& l, const std::string& m)
+@{
+ std::cerr << l << ": " << m << std::endl;
+@}
+
+void
+calcxx_driver::error (const std::string& m)
+@{
+ std::cerr << m << std::endl;
+@}
+@end example
+
+@node Calc++ Parser
+@subsubsection Calc++ Parser
+
+The parser definition file @file{calc++-parser.yy} starts by asking for
+the C++ LALR(1) skeleton, the creation of the parser header file, and
+specifies the name of the parser class. Because the C++ skeleton
+changed several times, it is safer to require the version you designed
+the grammar for.
+
+@comment file: calc++-parser.yy
+@example
+%skeleton "lalr1.cc" /* -*- C++ -*- */
+%require "@value{VERSION}"
+%defines
+%define parser_class_name "calcxx_parser"
+@end example
+
+@noindent
+@findex %code requires
+Then come the declarations/inclusions needed to define the
+@code{%union}. Because the parser uses the parsing driver and
+reciprocally, both cannot include the header of the other. Because the
+driver's header needs detailed knowledge about the parser class (in
+particular its inner types), it is the parser's header which will simply
+use a forward declaration of the driver.
+@xref{Decl Summary, ,%code}.
+
+@comment file: calc++-parser.yy
+@example
+%code requires @{
+# include <string>
+class calcxx_driver;
+@}
+@end example
+
+@noindent
+The driver is passed by reference to the parser and to the scanner.
+This provides a simple but effective pure interface, not relying on
+global variables.
+
+@comment file: calc++-parser.yy
+@example
+// The parsing context.
+%parse-param @{ calcxx_driver& driver @}
+%lex-param @{ calcxx_driver& driver @}
+@end example
+
+@noindent
+Then we request the location tracking feature, and initialize the
+first location's file name. Afterwards new locations are computed
+relatively to the previous locations: the file name will be
+automatically propagated.
+
+@comment file: calc++-parser.yy
+@example
+%locations
+%initial-action
+@{
+ // Initialize the initial location.
+ @@$.begin.filename = @@$.end.filename = &driver.file;
+@};
+@end example
+
+@noindent
+Use the two following directives to enable parser tracing and verbose
+error messages.
+
+@comment file: calc++-parser.yy
+@example
+%debug
+%error-verbose
+@end example
+
+@noindent
+Semantic values cannot use ``real'' objects, but only pointers to
+them.
+
+@comment file: calc++-parser.yy
+@example
+// Symbols.
+%union
+@{
+ int ival;
+ std::string *sval;
+@};
+@end example
+
+@noindent
+@findex %code
+The code between @samp{%code @{} and @samp{@}} is output in the
+@file{*.cc} file; it needs detailed knowledge about the driver.
+
+@comment file: calc++-parser.yy
+@example
+%code @{
+# include "calc++-driver.hh"
+@}
+@end example
+
+
+@noindent
+The token numbered as 0 corresponds to end of file; the following line
+allows for nicer error messages referring to ``end of file'' instead
+of ``$end''. Similarly user friendly named are provided for each
+symbol. Note that the tokens names are prefixed by @code{TOKEN_} to
+avoid name clashes.
+
+@comment file: calc++-parser.yy
+@example
+%token END 0 "end of file"
+%token ASSIGN ":="
+%token <sval> IDENTIFIER "identifier"
+%token <ival> NUMBER "number"
+%type <ival> exp
+@end example
+
+@noindent
+To enable memory deallocation during error recovery, use
+@code{%destructor}.
+
+@c FIXME: Document %printer, and mention that it takes a braced-code operand.
+@comment file: calc++-parser.yy
+@example
+%printer @{ debug_stream () << *$$; @} "identifier"
+%destructor @{ delete $$; @} "identifier"
+
+%printer @{ debug_stream () << $$; @} <ival>
+@end example
+
+@noindent
+The grammar itself is straightforward.
+
+@comment file: calc++-parser.yy
+@example
+%%
+%start unit;
+unit: assignments exp @{ driver.result = $2; @};
+
+assignments: assignments assignment @{@}
+ | /* Nothing. */ @{@};
+
+assignment:
+ "identifier" ":=" exp
+ @{ driver.variables[*$1] = $3; delete $1; @};
+
+%left '+' '-';
+%left '*' '/';
+exp: exp '+' exp @{ $$ = $1 + $3; @}
+ | exp '-' exp @{ $$ = $1 - $3; @}
+ | exp '*' exp @{ $$ = $1 * $3; @}
+ | exp '/' exp @{ $$ = $1 / $3; @}
+ | '(' exp ')' @{ $$ = $2; @}
+ | "identifier" @{ $$ = driver.variables[*$1]; delete $1; @}
+ | "number" @{ $$ = $1; @};
+%%
+@end example
+
+@noindent
+Finally the @code{error} member function registers the errors to the
+driver.
+
+@comment file: calc++-parser.yy
+@example
+void
+yy::calcxx_parser::error (const yy::calcxx_parser::location_type& l,
+ const std::string& m)
+@{
+ driver.error (l, m);
+@}
+@end example
+
+@node Calc++ Scanner
+@subsubsection Calc++ Scanner
+
+The Flex scanner first includes the driver declaration, then the
+parser's to get the set of defined tokens.
+
+@comment file: calc++-scanner.ll
+@example
+%@{ /* -*- C++ -*- */
+# include <cstdlib>
+# include <errno.h>
+# include <limits.h>
+# include <string>
+# include "calc++-driver.hh"
+# include "calc++-parser.hh"
+
+/* Work around an incompatibility in flex (at least versions
+ 2.5.31 through 2.5.33): it generates code that does
+ not conform to C89. See Debian bug 333231
+ <http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=333231>. */
+# undef yywrap
+# define yywrap() 1
+
+/* By default yylex returns int, we use token_type.
+ Unfortunately yyterminate by default returns 0, which is
+ not of token_type. */
+#define yyterminate() return token::END
+%@}
+@end example
+
+@noindent
+Because there is no @code{#include}-like feature we don't need
+@code{yywrap}, we don't need @code{unput} either, and we parse an
+actual file, this is not an interactive session with the user.
+Finally we enable the scanner tracing features.
+
+@comment file: calc++-scanner.ll
+@example
+%option noyywrap nounput batch debug
+@end example
+
+@noindent
+Abbreviations allow for more readable rules.
+
+@comment file: calc++-scanner.ll
+@example
+id [a-zA-Z][a-zA-Z_0-9]*
+int [0-9]+
+blank [ \t]
+@end example
+
+@noindent
+The following paragraph suffices to track locations accurately. Each
+time @code{yylex} is invoked, the begin position is moved onto the end
+position. Then when a pattern is matched, the end position is
+advanced of its width. In case it matched ends of lines, the end
+cursor is adjusted, and each time blanks are matched, the begin cursor
+is moved onto the end cursor to effectively ignore the blanks
+preceding tokens. Comments would be treated equally.
+
+@comment file: calc++-scanner.ll
+@example
+%@{
+# define YY_USER_ACTION yylloc->columns (yyleng);
+%@}
+%%
+%@{
+ yylloc->step ();
+%@}
+@{blank@}+ yylloc->step ();
+[\n]+ yylloc->lines (yyleng); yylloc->step ();
+@end example
+
+@noindent
+The rules are simple, just note the use of the driver to report errors.
+It is convenient to use a typedef to shorten
+@code{yy::calcxx_parser::token::identifier} into
+@code{token::identifier} for instance.
+
+@comment file: calc++-scanner.ll
+@example
+%@{
+ typedef yy::calcxx_parser::token token;
+%@}
+ /* Convert ints to the actual type of tokens. */
+[-+*/()] return yy::calcxx_parser::token_type (yytext[0]);
+":=" return token::ASSIGN;
+@{int@} @{
+ errno = 0;
+ long n = strtol (yytext, NULL, 10);
+ if (! (INT_MIN <= n && n <= INT_MAX && errno != ERANGE))
+ driver.error (*yylloc, "integer is out of range");
+ yylval->ival = n;
+ return token::NUMBER;
+@}
+@{id@} yylval->sval = new std::string (yytext); return token::IDENTIFIER;
+. driver.error (*yylloc, "invalid character");
+%%
+@end example
+
+@noindent
+Finally, because the scanner related driver's member function depend
+on the scanner's data, it is simpler to implement them in this file.
+
+@comment file: calc++-scanner.ll
+@example
+void
+calcxx_driver::scan_begin ()
+@{
+ yy_flex_debug = trace_scanning;
+ if (file == "-")
+ yyin = stdin;
+ else if (!(yyin = fopen (file.c_str (), "r")))
+ @{
+ error (std::string ("cannot open ") + file);
+ exit (1);
+ @}
+@}
+
+void
+calcxx_driver::scan_end ()
+@{
+ fclose (yyin);
+@}
+@end example
+
+@node Calc++ Top Level
+@subsubsection Calc++ Top Level
+
+The top level file, @file{calc++.cc}, poses no problem.
+
+@comment file: calc++.cc
+@example
+#include <iostream>
+#include "calc++-driver.hh"
+
+int
+main (int argc, char *argv[])
+@{
+ int res = 0;
+ calcxx_driver driver;
+ for (++argv; argv[0]; ++argv)
+ if (*argv == std::string ("-p"))
+ driver.trace_parsing = true;
+ else if (*argv == std::string ("-s"))
+ driver.trace_scanning = true;
+ else if (!driver.parse (*argv))
+ std::cout << driver.result << std::endl;
+ else
+ res = 1;
+ return res;
+@}
+@end example
+
+@node Java Parsers
+@section Java Parsers
+
+@menu
+* Java Bison Interface:: Asking for Java parser generation
+* Java Semantic Values:: %type and %token vs. Java
+* Java Location Values:: The position and location classes
+* Java Parser Interface:: Instantiating and running the parser
+* Java Scanner Interface:: Specifying the scanner for the parser
+* Java Action Features:: Special features for use in actions
+* Java Differences:: Differences between C/C++ and Java Grammars
+* Java Declarations Summary:: List of Bison declarations used with Java
+@end menu
+
+@node Java Bison Interface
+@subsection Java Bison Interface
+@c - %language "Java"
+
+(The current Java interface is experimental and may evolve.
+More user feedback will help to stabilize it.)
+
+The Java parser skeletons are selected using the @code{%language "Java"}
+directive or the @option{-L java}/@option{--language=java} option.
+
+@c FIXME: Documented bug.
+When generating a Java parser, @code{bison @var{basename}.y} will create
+a single Java source file named @file{@var{basename}.java}. Using an
+input file without a @file{.y} suffix is currently broken. The basename
+of the output file can be changed by the @code{%file-prefix} directive
+or the @option{-p}/@option{--name-prefix} option. The entire output file
+name can be changed by the @code{%output} directive or the
+@option{-o}/@option{--output} option. The output file contains a single
+class for the parser.
+
+You can create documentation for generated parsers using Javadoc.
+
+Contrary to C parsers, Java parsers do not use global variables; the
+state of the parser is always local to an instance of the parser class.
+Therefore, all Java parsers are ``pure'', and the @code{%pure-parser}
+and @code{%define api.pure} directives does not do anything when used in
+Java.
+
+Push parsers are currently unsupported in Java and @code{%define
+api.push_pull} have no effect.
+
+@acronym{GLR} parsers are currently unsupported in Java. Do not use the
+@code{glr-parser} directive.
+
+No header file can be generated for Java parsers. Do not use the
+@code{%defines} directive or the @option{-d}/@option{--defines} options.
+
+@c FIXME: Possible code change.
+Currently, support for debugging is always compiled
+in. Thus the @code{%debug} and @code{%token-table} directives and the
+@option{-t}/@option{--debug} and @option{-k}/@option{--token-table}
+options have no effect. This may change in the future to eliminate
+unused code in the generated parser, so use @code{%debug} explicitly
+if needed. Also, in the future the
+@code{%token-table} directive might enable a public interface to
+access the token names and codes.
+
+Getting a ``code too large'' error from the Java compiler means the code
+hit the 64KB bytecode per method limination of the Java class file.
+Try reducing the amount of code in actions and static initializers;
+otherwise, report a bug so that the parser skeleton will be improved.
+
+
+@node Java Semantic Values
+@subsection Java Semantic Values
+@c - No %union, specify type in %type/%token.
+@c - YYSTYPE
+@c - Printer and destructor
+
+There is no @code{%union} directive in Java parsers. Instead, the
+semantic values' types (class names) should be specified in the
+@code{%type} or @code{%token} directive:
+
+@example
+%type <Expression> expr assignment_expr term factor
+%type <Integer> number
+@end example
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