@value{UPDATED}), the @acronym{GNU} parser generator.
Copyright @copyright{} 1988, 1989, 1990, 1991, 1992, 1993, 1995, 1998,
-1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006 Free Software Foundation, Inc.
+1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007 Free Software Foundation, Inc.
@quotation
Permission is granted to copy, distribute and/or modify this document
messy for Bison to handle straightforwardly.
* Debugging:: Understanding or debugging Bison parsers.
* Invocation:: How to run Bison (to produce the parser source file).
-* C++ Language Interface:: Creating C++ parser objects.
+* Other Languages:: Creating C++ and Java parsers.
* FAQ:: Frequently Asked Questions
* Table of Symbols:: All the keywords of the Bison language are explained.
* Glossary:: Basic concepts are explained.
Outline of a Bison Grammar
* Prologue:: Syntax and usage of the prologue.
+* Prologue Alternatives:: Syntax and usage of alternatives to the prologue.
* Bison Declarations:: Syntax and usage of the Bison declarations section.
* Grammar Rules:: Syntax and usage of the grammar rules section.
* Epilogue:: Syntax and usage of the epilogue.
* Expect Decl:: Suppressing warnings about parsing conflicts.
* Start Decl:: Specifying the start symbol.
* Pure Decl:: Requesting a reentrant parser.
+* Push Decl:: Requesting a push parser.
* Decl Summary:: Table of all Bison declarations.
Parser C-Language Interface
* Option Cross Key:: Alphabetical list of long options.
* Yacc Library:: Yacc-compatible @code{yylex} and @code{main}.
-C++ Language Interface
+Parsers Written In Other Languages
* C++ Parsers:: The interface to generate C++ parser classes
-* A Complete C++ Example:: Demonstrating their use
+* Java Parsers:: The interface to generate Java parser classes
C++ Parsers
* 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
A Complete C++ Example
* Calc++ Scanner:: A pure C++ Flex scanner
* Calc++ Top Level:: Conducting the band
+Java Parsers
+
+* 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:: Java scanners, and pure parsers
+* Java Differences:: Differences between C/C++ and Java Grammars
+
Frequently Asked Questions
* Memory Exhausted:: Breaking the Stack Limits
Copying This Manual
-* GNU Free Documentation License:: License for copying this manual.
+* Copying This Manual:: License for copying this manual.
@end detailmenu
@end menu
exception@dots{}''. The text spells out the exact terms of the
exception.
-@include gpl.texi
+@node Copying
+@unnumbered GNU GENERAL PUBLIC LICENSE
+@include gpl-3.0.texi
@node Concepts
@chapter The Concepts of Bison
@}
@end group
@group
- | '-' exp %preg NEG @{ $$ = -$2; @}
+ | '-' exp %prec NEG @{ $$ = -$2; @}
| exp '^' exp @{ $$ = pow ($1, $3); @}
| '(' exp ')' @{ $$ = $2; @}
@end group
@menu
* Prologue:: Syntax and usage of the prologue.
+* Prologue Alternatives:: Syntax and usage of alternatives to the prologue.
* Bison Declarations:: Syntax and usage of the Bison declarations section.
* Grammar Rules:: Syntax and usage of the grammar rules section.
* Epilogue:: Syntax and usage of the epilogue.
feature test macros can affect the behavior of Bison-generated
@code{#include} directives.
-@findex %requires
+@node Prologue Alternatives
+@subsection Prologue Alternatives
+@cindex Prologue Alternatives
+
@findex %code
-If you've instructed Bison to generate a header file (@pxref{Table of Symbols,
-,%defines}), you probably want @code{#include "ptypes.h"} to appear
-in that header file as well.
-In that case, use @code{%requires}, @code{%provides}, and
-@code{%code} instead of @var{Prologue} sections
-(@pxref{Table of Symbols, ,%requires}):
+@findex %code requires
+@findex %code provides
+@findex %code top
+(The prologue alternatives described here are experimental.
+More user feedback will help to determine whether they should become permanent
+features.)
+
+The functionality of @var{Prologue} sections can often be subtle and
+inflexible.
+As an alternative, Bison provides a %code directive with an explicit qualifier
+field, which identifies the purpose of the code and thus the location(s) where
+Bison should generate it.
+For C/C++, the qualifier can be omitted for the default location, or it can be
+one of @code{requires}, @code{provides}, @code{top}.
+@xref{Decl Summary,,%code}.
+
+Look again at the example of the previous section:
@smallexample
-%requires @{
+%@{
+ #define _GNU_SOURCE
+ #include <stdio.h>
#include "ptypes.h"
+%@}
+
+%union @{
+ long int n;
+ tree t; /* @r{@code{tree} is defined in @file{ptypes.h}.} */
@}
+
+%@{
+ static void print_token_value (FILE *, int, YYSTYPE);
+ #define YYPRINT(F, N, L) print_token_value (F, N, L)
+%@}
+
+@dots{}
+@end smallexample
+
+@noindent
+Notice that there are two @var{Prologue} sections here, but there's a subtle
+distinction between their functionality.
+For example, if you decide to override Bison's default definition for
+@code{YYLTYPE}, in which @var{Prologue} section should you write your new
+definition?
+You should write it in the first since Bison will insert that code into the
+parser source code file @emph{before} the default @code{YYLTYPE} definition.
+In which @var{Prologue} section should you prototype an internal function,
+@code{trace_token}, that accepts @code{YYLTYPE} and @code{yytokentype} as
+arguments?
+You should prototype it in the second since Bison will insert that code
+@emph{after} the @code{YYLTYPE} and @code{yytokentype} definitions.
+
+This distinction in functionality between the two @var{Prologue} sections is
+established by the appearance of the @code{%union} between them.
+This behavior raises a few questions.
+First, why should the position of a @code{%union} affect definitions related to
+@code{YYLTYPE} and @code{yytokentype}?
+Second, what if there is no @code{%union}?
+In that case, the second kind of @var{Prologue} section is not available.
+This behavior is not intuitive.
+
+To avoid this subtle @code{%union} dependency, rewrite the example using a
+@code{%code top} and an unqualified @code{%code}.
+Let's go ahead and add the new @code{YYLTYPE} definition and the
+@code{trace_token} prototype at the same time:
+
+@smallexample
+%code top @{
+ #define _GNU_SOURCE
+ #include <stdio.h>
+
+ /* WARNING: The following code really belongs
+ * in a `%code requires'; see below. */
+
+ #include "ptypes.h"
+ #define YYLTYPE YYLTYPE
+ typedef struct YYLTYPE
+ @{
+ int first_line;
+ int first_column;
+ int last_line;
+ int last_column;
+ char *filename;
+ @} YYLTYPE;
+@}
+
%union @{
long int n;
tree t; /* @r{@code{tree} is defined in @file{ptypes.h}.} */
@}
%code @{
+ static void print_token_value (FILE *, int, YYSTYPE);
+ #define YYPRINT(F, N, L) print_token_value (F, N, L)
+ static void trace_token (enum yytokentype token, YYLTYPE loc);
+@}
+
+@dots{}
+@end smallexample
+
+@noindent
+In this way, @code{%code top} and the unqualified @code{%code} achieve the same
+functionality as the two kinds of @var{Prologue} sections, but it's always
+explicit which kind you intend.
+Moreover, both kinds are always available even in the absence of @code{%union}.
+
+The @code{%code top} block above logically contains two parts.
+The first two lines before the warning need to appear near the top of the
+parser source code file.
+The first line after the warning is required by @code{YYSTYPE} and thus also
+needs to appear in the parser source code file.
+However, if you've instructed Bison to generate a parser header file
+(@pxref{Decl Summary, ,%defines}), you probably want that line to appear before
+the @code{YYSTYPE} definition in that header file as well.
+The @code{YYLTYPE} definition should also appear in the parser header file to
+override the default @code{YYLTYPE} definition there.
+
+In other words, in the @code{%code top} block above, all but the first two
+lines are dependency code required by the @code{YYSTYPE} and @code{YYLTYPE}
+definitions.
+Thus, they belong in one or more @code{%code requires}:
+
+@smallexample
+%code top @{
+ #define _GNU_SOURCE
#include <stdio.h>
+@}
+%code requires @{
+ #include "ptypes.h"
+@}
+%union @{
+ long int n;
+ tree t; /* @r{@code{tree} is defined in @file{ptypes.h}.} */
+@}
+
+%code requires @{
+ #define YYLTYPE YYLTYPE
+ typedef struct YYLTYPE
+ @{
+ int first_line;
+ int first_column;
+ int last_line;
+ int last_column;
+ char *filename;
+ @} YYLTYPE;
+@}
+
+%code @{
+ static void print_token_value (FILE *, int, YYSTYPE);
+ #define YYPRINT(F, N, L) print_token_value (F, N, L)
+ static void trace_token (enum yytokentype token, YYLTYPE loc);
+@}
+
+@dots{}
+@end smallexample
+
+@noindent
+Now Bison will insert @code{#include "ptypes.h"} and the new @code{YYLTYPE}
+definition before the Bison-generated @code{YYSTYPE} and @code{YYLTYPE}
+definitions in both the parser source code file and the parser header file.
+(By the same reasoning, @code{%code requires} would also be the appropriate
+place to write your own definition for @code{YYSTYPE}.)
+
+When you are writing dependency code for @code{YYSTYPE} and @code{YYLTYPE}, you
+should prefer @code{%code requires} over @code{%code top} regardless of whether
+you instruct Bison to generate a parser header file.
+When you are writing code that you need Bison to insert only into the parser
+source code file and that has no special need to appear at the top of that
+file, you should prefer the unqualified @code{%code} over @code{%code top}.
+These practices will make the purpose of each block of your code explicit to
+Bison and to other developers reading your grammar file.
+Following these practices, we expect the unqualified @code{%code} and
+@code{%code requires} to be the most important of the four @var{Prologue}
+alternatives.
+
+At some point while developing your parser, you might decide to provide
+@code{trace_token} to modules that are external to your parser.
+Thus, you might wish for Bison to insert the prototype into both the parser
+header file and the parser source code file.
+Since this function is not a dependency required by @code{YYSTYPE} or
+@code{YYLTYPE}, it doesn't make sense to move its prototype to a
+@code{%code requires}.
+More importantly, since it depends upon @code{YYLTYPE} and @code{yytokentype},
+@code{%code requires} is not sufficient.
+Instead, move its prototype from the unqualified @code{%code} to a
+@code{%code provides}:
+
+@smallexample
+%code top @{
+ #define _GNU_SOURCE
+ #include <stdio.h>
+@}
+
+%code requires @{
+ #include "ptypes.h"
+@}
+%union @{
+ long int n;
+ tree t; /* @r{@code{tree} is defined in @file{ptypes.h}.} */
+@}
+
+%code requires @{
+ #define YYLTYPE YYLTYPE
+ typedef struct YYLTYPE
+ @{
+ int first_line;
+ int first_column;
+ int last_line;
+ int last_column;
+ char *filename;
+ @} YYLTYPE;
+@}
+
+%code provides @{
+ void trace_token (enum yytokentype token, YYLTYPE loc);
+@}
+
+%code @{
static void print_token_value (FILE *, int, YYSTYPE);
#define YYPRINT(F, N, L) print_token_value (F, N, L)
@}
@dots{}
@end smallexample
+@noindent
+Bison will insert the @code{trace_token} prototype into both the parser header
+file and the parser source code file after the definitions for
+@code{yytokentype}, @code{YYLTYPE}, and @code{YYSTYPE}.
+
+The above examples are careful to write directives in an order that reflects
+the layout of the generated parser source code and header files:
+@code{%code top}, @code{%code requires}, @code{%code provides}, and then
+@code{%code}.
+While your grammar files may generally be easier to read if you also follow
+this order, Bison does not require it.
+Instead, Bison lets you choose an organization that makes sense to you.
+
+You may declare any of these directives multiple times in the grammar file.
+In that case, Bison concatenates the contained code in declaration order.
+This is the only way in which the position of one of these directives within
+the grammar file affects its functionality.
+
+The result of the previous two properties is greater flexibility in how you may
+organize your grammar file.
+For example, you may organize semantic-type-related directives by semantic
+type:
+
+@smallexample
+%code requires @{ #include "type1.h" @}
+%union @{ type1 field1; @}
+%destructor @{ type1_free ($$); @} <field1>
+%printer @{ type1_print ($$); @} <field1>
+
+%code requires @{ #include "type2.h" @}
+%union @{ type2 field2; @}
+%destructor @{ type2_free ($$); @} <field2>
+%printer @{ type2_print ($$); @} <field2>
+@end smallexample
+
+@noindent
+You could even place each of the above directive groups in the rules section of
+the grammar file next to the set of rules that uses the associated semantic
+type.
+(In the rules section, you must terminate each of those directives with a
+semicolon.)
+And you don't have to worry that some directive (like a @code{%union}) in the
+definitions section is going to adversely affect their functionality in some
+counter-intuitive manner just because it comes first.
+Such an organization is not possible using @var{Prologue} sections.
+
+This section has been concerned with explaining the advantages of the four
+@var{Prologue} alternatives over the original Yacc @var{Prologue}.
+However, in most cases when using these directives, you shouldn't need to
+think about all the low-level ordering issues discussed here.
+Instead, you should simply use these directives to label each block of your
+code according to its purpose and let Bison handle the ordering.
+@code{%code} is the most generic label.
+Move code to @code{%code requires}, @code{%code provides}, or @code{%code top}
+as needed.
+
@node Bison Declarations
@subsection The Bison Declarations Section
@cindex Bison declarations (introduction)
* Expect Decl:: Suppressing warnings about parsing conflicts.
* Start Decl:: Specifying the start symbol.
* Pure Decl:: Requesting a reentrant parser.
+* Push Decl:: Requesting a push parser.
* Decl Summary:: Table of all Bison declarations.
@end menu
@subsection Freeing Discarded Symbols
@cindex freeing discarded symbols
@findex %destructor
-@findex %symbol-default
-
+@findex <*>
+@findex <>
During error recovery (@pxref{Error Recovery}), symbols already pushed
on the stack and tokens coming from the rest of the file are discarded
until the parser falls on its feet. If the parser runs out of memory,
When a symbol is listed among @var{symbols}, its @code{%destructor} is called a
per-symbol @code{%destructor}.
You may also define a per-type @code{%destructor} by listing a semantic type
-among @var{symbols}.
+tag among @var{symbols}.
In that case, the parser will invoke this @var{code} whenever it discards any
-grammar symbol that has that semantic type unless that symbol has its own
+grammar symbol that has that semantic type tag unless that symbol has its own
per-symbol @code{%destructor}.
-Finally, you may define a default @code{%destructor} by placing
-@code{%symbol-default} in the @var{symbols} list of exactly one
-@code{%destructor} declaration in your grammar file.
-In that case, the parser will invoke the associated @var{code} whenever it
-discards any user-defined grammar symbol for which there is no per-type or
-per-symbol @code{%destructor}.
+Finally, you can define two different kinds of default @code{%destructor}s.
+(These default forms are experimental.
+More user feedback will help to determine whether they should become permanent
+features.)
+You can place each of @code{<*>} and @code{<>} in the @var{symbols} list of
+exactly one @code{%destructor} declaration in your grammar file.
+The parser will invoke the @var{code} associated with one of these whenever it
+discards any user-defined grammar symbol that has no per-symbol and no per-type
+@code{%destructor}.
+The parser uses the @var{code} for @code{<*>} in the case of such a grammar
+symbol for which you have formally declared a semantic type tag (@code{%type}
+counts as such a declaration, but @code{$<tag>$} does not).
+The parser uses the @var{code} for @code{<>} in the case of such a grammar
+symbol that has no declared semantic type tag.
@end deffn
@noindent
-For instance:
+For example:
@smallexample
%union @{ char *string; @}
%union @{ char character; @}
%token <character> CHR
%type <character> chr
-%destructor @{ free ($$); @} %symbol-default
-%destructor @{ free ($$); printf ("%d", @@$.first_line); @} STRING1 string1
+%token TAGLESS
+
%destructor @{ @} <character>
+%destructor @{ free ($$); @} <*>
+%destructor @{ free ($$); printf ("%d", @@$.first_line); @} STRING1 string1
+%destructor @{ printf ("Discarding tagless symbol.\n"); @} <>
@end smallexample
@noindent
guarantees that, when the parser discards any user-defined symbol that has a
semantic type tag other than @code{<character>}, it passes its semantic value
-to @code{free}.
+to @code{free} by default.
However, when the parser discards a @code{STRING1} or a @code{string1}, it also
prints its line number to @code{stdout}.
It performs only the second @code{%destructor} in this case, so it invokes
@code{free} only once.
-
-Notice that a Bison-generated parser invokes the default @code{%destructor}
-only for user-defined as opposed to Bison-defined symbols.
-For example, the parser will not invoke it for the special Bison-defined
-symbols @code{$accept}, @code{$undefined}, or @code{$end} (@pxref{Table of
-Symbols, ,Bison Symbols}), none of which you can reference in your grammar.
-It also will not invoke it for the @code{error} token (@pxref{Table of Symbols,
-,error}), which is always defined by Bison regardless of whether you reference
-it in your grammar.
-However, it will invoke it for the end token (token 0) if you redefine it from
-@code{$end} to, for example, @code{END}:
+Finally, the parser merely prints a message whenever it discards any symbol,
+such as @code{TAGLESS}, that has no semantic type tag.
+
+A Bison-generated parser invokes the default @code{%destructor}s only for
+user-defined as opposed to Bison-defined symbols.
+For example, the parser will not invoke either kind of default
+@code{%destructor} for the special Bison-defined symbols @code{$accept},
+@code{$undefined}, or @code{$end} (@pxref{Table of Symbols, ,Bison Symbols}),
+none of which you can reference in your grammar.
+It also will not invoke either for the @code{error} token (@pxref{Table of
+Symbols, ,error}), which is always defined by Bison regardless of whether you
+reference it in your grammar.
+However, it may invoke one of them for the end token (token 0) if you
+redefine it from @code{$end} to, for example, @code{END}:
@smallexample
%token END 0
@end smallexample
+@cindex actions in mid-rule
+@cindex mid-rule actions
+Finally, Bison will never invoke a @code{%destructor} for an unreferenced
+mid-rule semantic value (@pxref{Mid-Rule Actions,,Actions in Mid-Rule}).
+That is, Bison does not consider a mid-rule to have a semantic value if you do
+not reference @code{$$} in the mid-rule's action or @code{$@var{n}} (where
+@var{n} is the RHS symbol position of the mid-rule) in any later action in that
+rule.
+However, if you do reference either, the Bison-generated parser will invoke the
+@code{<>} @code{%destructor} whenever it discards the mid-rule symbol.
+
@ignore
@noindent
In the future, it may be possible to redefine the @code{error} token as a
@code{YYABORT} or @code{YYACCEPT}, or failed error recovery, or memory
exhaustion.
-Right-hand size symbols of a rule that explicitly triggers a syntax
+Right-hand side symbols of a rule that explicitly triggers a syntax
error via @code{YYERROR} are not discarded automatically. As a rule
of thumb, destructors are invoked only when user actions cannot manage
the memory.
@code{yylloc} become local variables in @code{yyparse}, and a different
calling convention is used for the lexical analyzer function
@code{yylex}. @xref{Pure Calling, ,Calling Conventions for Pure
-Parsers}, for the details of this. The variable @code{yynerrs} also
-becomes local in @code{yyparse} (@pxref{Error Reporting, ,The Error
+Parsers}, for the details of this. The variable @code{yynerrs}
+becomes local in @code{yyparse} in pull mode but it becomes a member
+of yypstate in push mode. (@pxref{Error Reporting, ,The Error
Reporting Function @code{yyerror}}). The convention for calling
@code{yyparse} itself is unchanged.
You can generate either a pure parser or a nonreentrant parser from any
valid grammar.
+@node Push Decl
+@subsection A Push Parser
+@cindex push parser
+@cindex push parser
+@findex %define push_pull
+
+A pull parser is called once and it takes control until all its input
+is completely parsed. A push parser, on the other hand, is called
+each time a new token is made available.
+
+A push parser is typically useful when the parser is part of a
+main event loop in the client's application. This is typically
+a requirement of a GUI, when the main event loop needs to be triggered
+within a certain time period.
+
+Normally, Bison generates a pull parser.
+The following Bison declaration says that you want the parser to be a push
+parser (@pxref{Decl Summary,,%define push_pull}):
+
+@example
+%define push_pull "push"
+@end example
+
+In almost all cases, you want to ensure that your push parser is also
+a pure parser (@pxref{Pure Decl, ,A Pure (Reentrant) Parser}). The only
+time you should create an impure push parser is to have backwards
+compatibility with the impure Yacc pull mode interface. Unless you know
+what you are doing, your declarations should look like this:
+
+@example
+%pure-parser
+%define push_pull "push"
+@end example
+
+There is a major notable functional difference between the pure push parser
+and the impure push parser. It is acceptable for a pure push parser to have
+many parser instances, of the same type of parser, in memory at the same time.
+An impure push parser should only use one parser at a time.
+
+When a push parser is selected, Bison will generate some new symbols in
+the generated parser. @code{yypstate} is a structure that the generated
+parser uses to store the parser's state. @code{yypstate_new} is the
+function that will create a new parser instance. @code{yypstate_delete}
+will free the resources associated with the corresponding parser instance.
+Finally, @code{yypush_parse} is the function that should be called whenever a
+token is available to provide the parser. A trivial example
+of using a pure push parser would look like this:
+
+@example
+int status;
+yypstate *ps = yypstate_new ();
+do @{
+ status = yypush_parse (ps, yylex (), NULL);
+@} while (status == YYPUSH_MORE);
+yypstate_delete (ps);
+@end example
+
+If the user decided to use an impure push parser, a few things about
+the generated parser will change. The @code{yychar} variable becomes
+a global variable instead of a variable in the @code{yypush_parse} function.
+For this reason, the signature of the @code{yypush_parse} function is
+changed to remove the token as a parameter. A nonreentrant push parser
+example would thus look like this:
+
+@example
+extern int yychar;
+int status;
+yypstate *ps = yypstate_new ();
+do @{
+ yychar = yylex ();
+ status = yypush_parse (ps);
+@} while (status == YYPUSH_MORE);
+yypstate_delete (ps);
+@end example
+
+That's it. Notice the next token is put into the global variable @code{yychar}
+for use by the next invocation of the @code{yypush_parse} function.
+
+Bison also supports both the push parser interface along with the pull parser
+interface in the same generated parser. In order to get this functionality,
+you should replace the @code{%define push_pull "push"} declaration with the
+@code{%define push_pull "both"} declaration. Doing this will create all of the
+symbols mentioned earlier along with the two extra symbols, @code{yyparse}
+and @code{yypull_parse}. @code{yyparse} can be used exactly as it normally
+would be used. However, the user should note that it is implemented in the
+generated parser by calling @code{yypull_parse}.
+This makes the @code{yyparse} function that is generated with the
+@code{%define push_pull "both"} declaration slower than the normal
+@code{yyparse} function. If the user
+calls the @code{yypull_parse} function it will parse the rest of the input
+stream. It is possible to @code{yypush_parse} tokens to select a subgrammar
+and then @code{yypull_parse} the rest of the input stream. If you would like
+to switch back and forth between between parsing styles, you would have to
+write your own @code{yypull_parse} function that knows when to quit looking
+for input. An example of using the @code{yypull_parse} function would look
+like this:
+
+@example
+yypstate *ps = yypstate_new ();
+yypull_parse (ps); /* Will call the lexer */
+yypstate_delete (ps);
+@end example
+
+Adding the @code{%pure-parser} declaration does exactly the same thing to the
+generated parser with @code{%define push_pull "both"} as it did for
+@code{%define push_pull "push"}.
+
@node Decl Summary
@subsection Bison Declaration Summary
@cindex Bison declaration summary
In order to change the behavior of @command{bison}, use the following
directives:
+@deffn {Directive} %code @{@var{code}@}
+@findex %code
+This is the unqualified form of the @code{%code} directive.
+It inserts @var{code} verbatim at a language-dependent default location in the
+output@footnote{The default location is actually skeleton-dependent;
+ writers of non-standard skeletons however should choose the default location
+ consistently with the behavior of the standard Bison skeletons.}.
+
+@cindex Prologue
+For C/C++, the default location is the parser source code
+file after the usual contents of the parser header file.
+Thus, @code{%code} replaces the traditional Yacc prologue,
+@code{%@{@var{code}%@}}, for most purposes.
+For a detailed discussion, see @ref{Prologue Alternatives}.
+
+For Java, the default location is inside the parser class.
+
+(Like all the Yacc prologue alternatives, this directive is experimental.
+More user feedback will help to determine whether it should become a permanent
+feature.)
+@end deffn
+
+@deffn {Directive} %code @var{qualifier} @{@var{code}@}
+This is the qualified form of the @code{%code} directive.
+If you need to specify location-sensitive verbatim @var{code} that does not
+belong at the default location selected by the unqualified @code{%code} form,
+use this form instead.
+
+@var{qualifier} identifies the purpose of @var{code} and thus the location(s)
+where Bison should generate it.
+Not all values of @var{qualifier} are available for all target languages:
+
+@itemize @bullet
+@item requires
+@findex %code requires
+
+@itemize @bullet
+@item Language(s): C, C++
+
+@item Purpose: This is the best place to write dependency code required for
+@code{YYSTYPE} and @code{YYLTYPE}.
+In other words, it's the best place to define types referenced in @code{%union}
+directives, and it's the best place to override Bison's default @code{YYSTYPE}
+and @code{YYLTYPE} definitions.
+
+@item Location(s): The parser header file and the parser source code file
+before the Bison-generated @code{YYSTYPE} and @code{YYLTYPE} definitions.
+@end itemize
+
+@item provides
+@findex %code provides
+
+@itemize @bullet
+@item Language(s): C, C++
+
+@item Purpose: This is the best place to write additional definitions and
+declarations that should be provided to other modules.
+
+@item Location(s): The parser header file and the parser source code file after
+the Bison-generated @code{YYSTYPE}, @code{YYLTYPE}, and token definitions.
+@end itemize
+
+@item top
+@findex %code top
+
+@itemize @bullet
+@item Language(s): C, C++
+
+@item Purpose: The unqualified @code{%code} or @code{%code requires} should
+usually be more appropriate than @code{%code top}.
+However, occasionally it is necessary to insert code much nearer the top of the
+parser source code file.
+For example:
+
+@smallexample
+%code top @{
+ #define _GNU_SOURCE
+ #include <stdio.h>
+@}
+@end smallexample
+
+@item Location(s): Near the top of the parser source code file.
+@end itemize
+
+@item imports
+@findex %code imports
+
+@itemize @bullet
+@item Language(s): Java
+
+@item Purpose: This is the best place to write Java import directives.
+
+@item Location(s): The parser Java file after any Java package directive and
+before any class definitions.
+@end itemize
+@end itemize
+
+(Like all the Yacc prologue alternatives, this directive is experimental.
+More user feedback will help to determine whether it should become a permanent
+feature.)
+
+@cindex Prologue
+For a detailed discussion of how to use @code{%code} in place of the
+traditional Yacc prologue for C/C++, see @ref{Prologue Alternatives}.
+@end deffn
+
@deffn {Directive} %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.
@end deffn
@xref{Tracing, ,Tracing Your Parser}.
+@deffn {Directive} %define @var{variable}
+@deffnx {Directive} %define @var{variable} "@var{value}"
+Define a variable to adjust Bison's behavior.
+The possible choices for @var{variable}, as well as their meanings, depend on
+the selected target language and/or the parser skeleton (@pxref{Decl
+Summary,,%language}).
+
+Bison will warn if a @var{variable} is defined multiple times.
+
+Omitting @code{"@var{value}"} is always equivalent to specifying it as
+@code{""}.
+
+Some @var{variable}s may be used as Booleans.
+In this case, Bison will complain if the variable definition does not meet one
+of the following four conditions:
+
+@enumerate
+@item @code{"@var{value}"} is @code{"true"}
+
+@item @code{"@var{value}"} is omitted (or is @code{""}).
+This is equivalent to @code{"true"}.
+
+@item @code{"@var{value}"} is @code{"false"}.
+
+@item @var{variable} is never defined.
+In this case, Bison selects a default value, which may depend on the selected
+target language and/or parser skeleton.
+@end enumerate
+
+Some of the accepted @var{variable}s are:
+
+@itemize @bullet
+@item push_pull
+@findex %define push_pull
+
+@itemize @bullet
+@item Language(s): C (LALR(1) only)
+
+@item Purpose: Requests a pull parser, a push parser, or both.
+@xref{Push Decl, ,A Push Parser}.
+
+@item Accepted Values: @code{"pull"}, @code{"push"}, @code{"both"}
+
+@item Default Value: @code{"pull"}
+@end itemize
+
+@item lr.keep_unreachable_states
+@findex %define lr.keep_unreachable_states
+
+@itemize @bullet
+@item Language(s): all
+
+@item Purpose: Requests that Bison allow unreachable parser states to remain in
+the parser tables.
+Bison considers a state to be unreachable if there exists no sequence of
+transitions from the start state to that state.
+A state can become unreachable during conflict resolution if Bison disables a
+shift action leading to it from a predecessor state.
+Keeping unreachable states is sometimes useful for analysis purposes, but they
+are useless in the generated parser.
+
+@item Accepted Values: Boolean
+
+@item Default Value: @code{"false"}
+
+@item Caveats:
+
+@itemize @bullet
+@item Unreachable states may contain conflicts and may reduce rules not
+reduced in any other state.
+Thus, keeping unreachable states may induce warnings that are irrelevant to
+your parser's behavior, and it may eliminate warnings that are relevant.
+Of course, the change in warnings may actually be relevant to a parser table
+analysis that wants to keep unreachable states, so this behavior will likely
+remain in future Bison releases.
+
+@item While Bison is able to remove unreachable states, it is not guaranteed to
+remove other kinds of useless states.
+Specifically, when Bison disables reduce actions during conflict resolution,
+some goto actions may become useless, and thus some additional states may
+become useless.
+If Bison were to compute which goto actions were useless and then disable those
+actions, it could identify such states as unreachable and then remove those
+states.
+However, Bison does not compute which goto actions are useless.
+@end itemize
+@end itemize
+
+@item namespace
+@findex %define namespace
+
+@itemize
+@item Languages(s): C++
+
+@item Purpose: Specifies the namespace for the parser class.
+For example, if you specify:
+
+@smallexample
+%define namespace "foo::bar"
+@end smallexample
+
+Bison uses @code{foo::bar} verbatim in references such as:
+
+@smallexample
+foo::bar::parser::semantic_type
+@end smallexample
+
+However, to open a namespace, Bison removes any leading @code{::} and then
+splits on any remaining occurrences:
+
+@smallexample
+namespace foo @{ namespace bar @{
+ class position;
+ class location;
+@} @}
+@end smallexample
+
+@item Accepted Values: Any absolute or relative C++ namespace reference without
+a trailing @code{"::"}.
+For example, @code{"foo"} or @code{"::foo::bar"}.
+
+@item Default Value: The value specified by @code{%name-prefix}, which defaults
+to @code{yy}.
+This usage of @code{%name-prefix} is for backward compatibility and can be
+confusing since @code{%name-prefix} also specifies the textual prefix for the
+lexical analyzer function.
+Thus, if you specify @code{%name-prefix}, it is best to also specify
+@code{%define namespace} so that @code{%name-prefix} @emph{only} affects the
+lexical analyzer function.
+For example, if you specify:
+
+@smallexample
+%define namespace "foo"
+%name-prefix "bar::"
+@end smallexample
+
+The parser namespace is @code{foo} and @code{yylex} is referenced as
+@code{bar::lex}.
+@end itemize
+@end itemize
+
+@end deffn
+
@deffn {Directive} %defines
Write a header file containing macro definitions for the token type
names defined in the grammar as well as a few other declarations.
and to the token type codes. @xref{Token Values, ,Semantic Values of
Tokens}.
-@findex %requires
-@findex %provides
-If you have declared @code{%requires} or @code{%provides}, the output
+@findex %code requires
+@findex %code provides
+If you have declared @code{%code requires} or @code{%code provides}, the output
header also contains their code.
-@xref{Table of Symbols, ,%requires}.
+@xref{Decl Summary, ,%code}.
+@end deffn
+
+@deffn {Directive} %defines @var{defines-file}
+Same as above, but save in the file @var{defines-file}.
@end deffn
@deffn {Directive} %destructor
discarded symbols. @xref{Destructor Decl, , Freeing Discarded Symbols}.
@end deffn
-@deffn {Directive} %file-prefix="@var{prefix}"
+@deffn {Directive} %file-prefix "@var{prefix}"
Specify a prefix to use for all Bison output file names. The names are
chosen as if the input file were named @file{@var{prefix}.y}.
@end deffn
+@deffn {Directive} %language "@var{language}"
+Specify the programming language for the generated parser. Currently
+supported languages include C and C++.
+@var{language} is case-insensitive.
+@end deffn
+
@deffn {Directive} %locations
Generate the code processing the locations (@pxref{Action Features,
,Special Features for Use in Actions}). This mode is enabled as soon as
accurate syntax error messages.
@end deffn
-@deffn {Directive} %name-prefix="@var{prefix}"
+@deffn {Directive} %name-prefix "@var{prefix}"
Rename the external symbols used in the parser so that they start with
@var{prefix} instead of @samp{yy}. The precise list of symbols renamed
in C parsers
is @code{yyparse}, @code{yylex}, @code{yyerror}, @code{yynerrs},
@code{yylval}, @code{yychar}, @code{yydebug}, and
-(if locations are used) @code{yylloc}. For example, if you use
-@samp{%name-prefix="c_"}, the names become @code{c_parse}, @code{c_lex},
-and so on. In C++ parsers, it is only the surrounding namespace which is
-named @var{prefix} instead of @samp{yy}.
+(if locations are used) @code{yylloc}. If you use a push parser,
+@code{yypush_parse}, @code{yypull_parse}, @code{yypstate},
+@code{yypstate_new} and @code{yypstate_delete} will
+also be renamed. For example, if you use @samp{%name-prefix "c_"}, the
+names become @code{c_parse}, @code{c_lex}, and so on.
+For C++ parsers, see the @code{%define namespace} documentation in this
+section.
@xref{Multiple Parsers, ,Multiple Parsers in the Same Program}.
@end deffn
@end deffn
@end ifset
-@deffn {Directive} %no-parser
-Do not include any C code in the parser file; generate tables only. The
-parser file contains just @code{#define} directives and static variable
-declarations.
-
-This option also tells Bison to write the C code for the grammar actions
-into a file named @file{@var{file}.act}, in the form of a
-brace-surrounded body fit for a @code{switch} statement.
-@end deffn
-
@deffn {Directive} %no-lines
Don't generate any @code{#line} preprocessor commands in the parser
file. Ordinarily Bison writes these commands in the parser file so that
file in its own right.
@end deffn
-@deffn {Directive} %output="@var{file}"
+@deffn {Directive} %output "@var{file}"
Specify @var{file} for the parser file.
@end deffn
Require a Version of Bison}.
@end deffn
+@deffn {Directive} %skeleton "@var{file}"
+Specify the skeleton to use.
+
+You probably don't need this option unless you are developing Bison.
+You should use @code{%language} if you want to specify the skeleton for a
+different language, because it is clearer and because it will always 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
+directory of the grammar file.
+This is similar to how most shells resolve commands.
+@end deffn
+
@deffn {Directive} %token-table
Generate an array of token names in the parser file. The name of the
array is @code{yytname}; @code{yytname[@var{i}]} is the name of the
The precise list of symbols renamed is @code{yyparse}, @code{yylex},
@code{yyerror}, @code{yynerrs}, @code{yylval}, @code{yylloc},
-@code{yychar} and @code{yydebug}. For example, if you use @samp{-p c},
-the names become @code{cparse}, @code{clex}, and so on.
+@code{yychar} and @code{yydebug}. If you use a push parser,
+@code{yypush_parse}, @code{yypull_parse}, @code{yypstate},
+@code{yypstate_new} and @code{yypstate_delete} will also be renamed.
+For example, if you use @samp{-p c}, the names become @code{cparse},
+@code{clex}, and so on.
@strong{All the other variables and macros associated with Bison are not
renamed.} These others are not global; there is no conflict if the same
@menu
* Parser Function:: How to call @code{yyparse} and what it returns.
+* Push Parser Function:: How to call @code{yypush_parse} and what it returns.
+* Pull Parser Function:: How to call @code{yypull_parse} and what it returns.
+* Parser Create Function:: How to call @code{yypstate_new} and what it
+ returns.
+* Parser Delete Function:: How to call @code{yypstate_delete} and what it
+ returns.
* Lexical:: You must supply a function @code{yylex}
which reads tokens.
* Error Reporting:: You must supply a function @code{yyerror}.
exp: @dots{} @{ @dots{}; *randomness += 1; @dots{} @}
@end example
+@node Push Parser Function
+@section The Push Parser Function @code{yypush_parse}
+@findex yypush_parse
+
+You call the function @code{yypush_parse} to parse a single token. This
+function is available if either the @code{%define push_pull "push"} or
+@code{%define push_pull "both"} declaration is used.
+@xref{Push Decl, ,A Push Parser}.
+
+@deftypefun int yypush_parse (yypstate *yyps)
+The value returned by @code{yypush_parse} is the same as for yyparse with the
+following exception. @code{yypush_parse} will return YYPUSH_MORE if more input
+is required to finish parsing the grammar.
+@end deftypefun
+
+@node Pull Parser Function
+@section The Pull Parser Function @code{yypull_parse}
+@findex yypull_parse
+
+You call the function @code{yypull_parse} to parse the rest of the input
+stream. This function is available if the @code{%define push_pull "both"}
+declaration is used.
+@xref{Push Decl, ,A Push Parser}.
+
+@deftypefun int yypull_parse (yypstate *yyps)
+The value returned by @code{yypull_parse} is the same as for @code{yyparse}.
+@end deftypefun
+
+@node Parser Create Function
+@section The Parser Create Function @code{yystate_new}
+@findex yypstate_new
+
+You call the function @code{yypstate_new} to create a new parser instance.
+This function is available if either the @code{%define push_pull "push"} or
+@code{%define push_pull "both"} declaration is used.
+@xref{Push Decl, ,A Push Parser}.
+
+@deftypefun yypstate *yypstate_new (void)
+The fuction will return a valid parser instance if there was memory available
+or NULL if no memory was available.
+@end deftypefun
+
+@node Parser Delete Function
+@section The Parser Delete Function @code{yystate_delete}
+@findex yypstate_delete
+
+You call the function @code{yypstate_delete} to delete a parser instance.
+function is available if either the @code{%define push_pull "push"} or
+@code{%define push_pull "both"} declaration is used.
+@xref{Push Decl, ,A Push Parser}.
+
+@deftypefun void yypstate_delete (yypstate *yyps)
+This function will reclaim the memory associated with a parser instance.
+After this call, you should no longer attempt to use the parser instance.
+@end deftypefun
@node Lexical
@section The Lexical Analyzer Function @code{yylex}
@example
state 8
- exp -> exp . '+' exp [$, '+', '-', '/'] (rule 1)
+ exp -> exp . '+' exp (rule 1)
exp -> exp '+' exp . [$, '+', '-', '/'] (rule 1)
exp -> exp . '-' exp (rule 2)
exp -> exp . '*' exp (rule 3)
The trace facility outputs messages with macro calls of the form
@code{YYFPRINTF (stderr, @var{format}, @var{args})} where
-@var{format} and @var{args} are the usual @code{printf} format and
+@var{format} and @var{args} are the usual @code{printf} format and variadic
arguments. If you define @code{YYDEBUG} to a nonzero value but do not
define @code{YYFPRINTF}, @code{<stdio.h>} is automatically included
and @code{YYFPRINTF} is defined to @code{fprintf}.
@item --print-localedir
Print the name of the directory containing locale-dependent data.
+@item --print-datadir
+Print the name of the directory containing skeletons and XSLT.
+
@item -y
@itemx --yacc
Act more like the traditional Yacc command. This can cause
Tuning the parser:
@table @option
-@item -S @var{file}
-@itemx --skeleton=@var{file}
-Specify the skeleton to use. You probably don't need this option unless
-you are developing Bison.
-
@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 -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 and C++.
+@var{language} is case-insensitive.
+
@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.
+Pretend that @code{%name-prefix "@var{prefix}"} was specified.
@xref{Decl Summary}.
@item -l
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 -n
-@itemx --no-parser
-Pretend that @code{%no-parser} was specified. @xref{Decl Summary}.
+@item -S @var{file}
+@itemx --skeleton=@var{file}
+Specify the skeleton to use, similar to @code{%skeleton}
+(@pxref{Decl Summary, , Bison Declaration Summary}).
+
+You probably don't need this option unless you are developing Bison.
+You should use @option{--language} if you want to specify the skeleton for a
+different language, because it is clearer and because it will always
+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
@item @option{--help} @tab @option{-h}
@item @option{--name-prefix=@var{prefix}} @tab @option{-p @var{name-prefix}}
@item @option{--no-lines} @tab @option{-l}
-@item @option{--no-parser} @tab @option{-n}
@item @option{--output=@var{outfile}} @tab @option{-o @var{outfile}}
@item @option{--print-localedir} @tab
+@item @option{--print-datadir} @tab
@item @option{--token-table} @tab @option{-k}
@item @option{--verbose} @tab @option{-v}
@item @option{--version} @tab @option{-V}
@c ================================================= C++ Bison
-@node C++ Language Interface
-@chapter C++ Language Interface
+@node Other Languages
+@chapter Parsers Written In Other Languages
@menu
* C++ Parsers:: The interface to generate C++ parser classes
-* A Complete C++ Example:: Demonstrating their use
+* Java Parsers:: The interface to generate Java parser classes
@end menu
@node C++ Parsers
* 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 - %language "C++"
@c - Always pure
@c - initial action
-The C++ parser @acronym{LALR}(1) skeleton is named @file{lalr1.cc}. To
-select it, you may either pass the option @option{--skeleton=lalr1.cc}
-to Bison, or include the directive @samp{%skeleton "lalr1.cc"} in the
-grammar preamble. When run, @command{bison} will create several
-entities in the @samp{yy} namespace. Use the @samp{%name-prefix}
-directive to change the namespace name, see @ref{Decl Summary}. The
-various classes are generated in the following files:
+The C++ @acronym{LALR}(1) parser is selected using the language directive,
+@samp{%language "C++"}, or the synonymous command-line option
+@option{--language=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
@node C++ Semantic Values
@subsection C++ Semantic Values
@c - No objects in unions
-@c - YSTYPE
+@c - YYSTYPE
@c - Printer and destructor
The @code{%union} directive works as for C, see @ref{Union Decl, ,The
@c - %locations
@c - class Position
@c - class Location
-@c - %define "filename_type" "const symbol::Symbol"
+@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
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}"}.
+filename_type "@var{type}"}.
@end deftypemethod
@deftypemethod {position} {unsigned int} line
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
+@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
@node A Complete C++ Example
-@section 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,
@end menu
@node Calc++ --- C++ Calculator
-@subsection Calc++ --- C++ Calculator
+@subsubsection Calc++ --- C++ Calculator
Of course the grammar is dedicated to arithmetics, a single
expression, possibly preceded by variable assignments. An
@end example
@node Calc++ Parsing Driver
-@subsection Calc++ Parsing Driver
+@subsubsection Calc++ Parsing Driver
@c - An env
@c - A place to store error messages
@c - A place for the result
@comment file: calc++-driver.hh
@example
- // Handling the parser.
- void parse (const std::string& f);
+ // Run the parser. Return 0 on success.
+ int parse (const std::string& f);
std::string file;
bool trace_parsing;
@end example
@{
@}
-void
+int
calcxx_driver::parse (const std::string &f)
@{
file = f;
scan_begin ();
yy::calcxx_parser parser (*this);
parser.set_debug_level (trace_parsing);
- parser.parse ();
+ int res = parser.parse ();
scan_end ();
+ return res;
@}
void
@end example
@node Calc++ Parser
-@subsection 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
@comment file: calc++-parser.yy
@example
-%skeleton "lalr1.cc" /* -*- C++ -*- */
-%require "2.1a"
+%language "C++" /* -*- C++ -*- */
+%require "@value{VERSION}"
%defines
-%define "parser_class_name" "calcxx_parser"
+%define parser_class_name "calcxx_parser"
@end example
@noindent
-@findex %requires
+@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{Table of Symbols, ,%requires}.
+@xref{Decl Summary, ,%code}.
@comment file: calc++-parser.yy
@example
-%requires @{
+%code requires @{
# include <string>
class calcxx_driver;
@}
%token ASSIGN ":="
%token <sval> IDENTIFIER "identifier"
%token <ival> NUMBER "number"
-%type <ival> exp "expression"
+%type <ival> exp
@end example
@noindent
%printer @{ debug_stream () << *$$; @} "identifier"
%destructor @{ delete $$; @} "identifier"
-%printer @{ debug_stream () << $$; @} "number" "expression"
+%printer @{ debug_stream () << $$; @} <ival>
@end example
@noindent
@end example
@node Calc++ Scanner
-@subsection Calc++ Scanner
+@subsubsection Calc++ Scanner
The Flex scanner first includes the driver declaration, then the
parser's to get the set of defined tokens.
calcxx_driver::scan_begin ()
@{
yy_flex_debug = trace_scanning;
- if (!(yyin = fopen (file.c_str (), "r")))
- error (std::string ("cannot open ") + file);
+ if (file == "-")
+ yyin = stdin;
+ else if (!(yyin = fopen (file.c_str (), "r")))
+ @{
+ error (std::string ("cannot open ") + file);
+ exit (1);
+ @}
@}
void
@end example
@node Calc++ Top Level
-@subsection Calc++ Top Level
+@subsubsection Calc++ Top Level
The top level file, @file{calc++.cc}, poses no problem.
driver.trace_parsing = true;
else if (*argv == std::string ("-s"))
driver.trace_scanning = true;
- else
- @{
- driver.parse (*argv);
- std::cout << driver.result << std::endl;
- @}
+ else if (!driver.parse (*argv))
+ std::cout << driver.result << std::endl;
@}
@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:: Java scanners, and pure parsers
+* Java Differences:: Differences between C/C++ and Java Grammars
+@end menu
+
+@node Java Bison Interface
+@subsection Java Bison Interface
+@c - %language "Java"
+@c - initial action
+
+The Java parser skeletons are selected using a language directive,
+@samp{%language "Java"}, or the synonymous command-line option
+@option{--language=java}.
+
+When run, @command{bison} will create several entities whose name
+starts with @samp{YY}. Use the @samp{%name-prefix} directive to
+change the prefix, see @ref{Decl Summary}; classes can be placed
+in an arbitrary Java package using a @samp{%define package} section.
+
+The parser class defines an inner class, @code{Location}, that is used
+for location tracking. If the parser is pure, it also defines an
+inner interface, @code{Lexer}; see~@ref{Java Scanner Interface} for the
+meaning of pure parsers when the Java language is chosen. Other than
+these inner class/interface, and the members described in~@ref{Java
+Parser Interface}, all the other members and fields are preceded
+with a @code{yy} prefix to avoid clashes with user code.
+
+No header file can be generated for Java parsers; you must not pass
+@option{-d}/@option{--defines} to @command{bison}, nor use the
+@samp{%defines} directive.
+
+By default, the @samp{YYParser} class has package visibility. A
+declaration @samp{%define "public"} will change to public visibility.
+Remember that, according to the Java language specification, the name
+of the @file{.java} file should match the name of the class in this
+case.
+
+Similarly, a declaration @samp{%define "abstract"} will make your
+class abstract.
+
+You can create documentation for generated parsers using Javadoc.
+
+@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
+
+By default, the semantic stack is declared to have @code{Object} members,
+which means that the class types you specify can be of any class.
+To improve the type safety of the parser, you can declare the common
+superclass of all the semantic values using the @samp{%define} directive.
+For example, after the following declaration:
+
+@example
+%define "stype" "ASTNode"
+@end example
+
+@noindent
+any @code{%type} or @code{%token} specifying a semantic type which
+is not a subclass of ASTNode, will cause a compile-time error.
+
+Types used in the directives may be qualified with a package name.
+Primitive data types are accepted for Java version 1.5 or later. Note
+that in this case the autoboxing feature of Java 1.5 will be used.
+
+Java parsers do not support @code{%destructor}, since the language
+adopts garbage collection. The parser will try to hold references
+to semantic values for as little time as needed.
+
+Java parsers do not support @code{%printer}, as @code{toString()}
+can be used to print the semantic values. This however may change
+(in a backwards-compatible way) in future versions of Bison.
+
+
+@node Java Location Values
+@subsection Java Location Values
+@c - %locations
+@c - class Position
+@c - class Location
+
+When the directive @code{%locations} is used, the Java parser
+supports location tracking, see @ref{Locations, , Locations Overview}.
+An auxiliary user-defined class defines a @dfn{position}, a single point
+in a file; Bison itself defines a class representing a @dfn{location},
+a range composed of a pair of positions (possibly spanning several
+files). The location class is an inner class of the parser; the name
+is @code{Location} by default, may also be renamed using @code{%define
+"location_type" "@var{class-name}}.
+
+The location class treats the position as a completely opaque value.
+By default, the class name is @code{Position}, but this can be changed
+with @code{%define "position_type" "@var{class-name}"}.
+
+
+@deftypemethod {Location} {Position} begin
+@deftypemethodx {Location} {Position} end
+The first, inclusive, position of the range, and the first beyond.
+@end deftypemethod
+
+@deftypemethod {Location} {void} toString ()
+Prints the range represented by the location. For this to work
+properly, the position class should override the @code{equals} and
+@code{toString} methods appropriately.
+@end deftypemethod
+
+
+@node Java Parser Interface
+@subsection Java 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 file defines the parser class in the package optionally
+indicated in the @code{%define package} section. The class name defaults
+to @code{YYParser}. The @code{YY} prefix may be changed using
+@samp{%name-prefix}; alternatively, you can use @samp{%define
+"parser_class_name" "@var{name}"} to give a custom name to the class.
+The interface of this class is detailed below. It can be extended using
+the @code{%parse-param} directive; each occurrence of the directive will
+add a field to the parser class, and an argument to its constructor.
+
+@deftypemethod {YYParser} {} YYParser (@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 {YYParser} {boolean} parse ()
+Run the syntactic analysis, and return @code{true} on success,
+@code{false} otherwise.
+@end deftypemethod
+
+@deftypemethod {YYParser} {boolean} recovering ()
+During the syntactic analysis, return @code{true} if recovering
+from a syntax error. @xref{Error Recovery}.
+@end deftypemethod
+
+@deftypemethod {YYParser} {java.io.PrintStream} getDebugStream ()
+@deftypemethodx {YYParser} {void} setDebugStream (java.io.printStream @var{o})
+Get or set the stream used for tracing the parsing. It defaults to
+@code{System.err}.
+@end deftypemethod
+
+@deftypemethod {YYParser} {int} getDebugLevel ()
+@deftypemethodx {YYParser} {void} setDebugLevel (int @var{l})
+Get or set the tracing level. Currently its value is either 0, no trace,
+or nonzero, full tracing.
+@end deftypemethod
+
+@deftypemethod {YYParser} {void} error (Location @var{l}, String @var{m})
+The definition for this member function must be supplied by the user
+in the same way as the scanner interface (@pxref{Java Scanner
+Interface}); the parser uses it to report a parser error occurring at
+@var{l}, described by @var{m}.
+@end deftypemethod
+
+
+@node Java Scanner Interface
+@subsection Java Scanner Interface
+@c - %code lexer
+@c - %lex-param
+@c - Lexer interface
+
+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}
+directive does not do anything when used in Java.
+
+The scanner always resides in a separate class than the parser.
+Still, Java also two possible ways to interface a Bison-generated Java
+parser with a scanner, that is, the scanner may reside in a separate file
+than the Bison grammar, or in the same file. The interface
+to the scanner is similar in the two cases.
+
+In the first case, where the scanner in the same file as the grammar, the
+scanner code has to be placed in @code{%code lexer} blocks. If you want
+to pass parameters from the parser constructor to the scanner constructor,
+specify them with @code{%lex-param}; they are passed before
+@code{%parse-param}s to the constructor.
+
+In the second case, the scanner has to implement interface @code{Lexer},
+which is defined within the parser class (e.g., @code{YYParser.Lexer}).
+The constructor of the parser object will then accept an object
+implementing the interface; @code{%lex-param} is not used in this
+case.
+
+In both cases, the scanner has to implement the following methods.
+
+@deftypemethod {Lexer} {void} yyerror (Location @var{l}, String @var{m})
+As explained in @pxref{Java Parser Interface}, this method is defined
+by the user to emit an error message. The first parameter is omitted
+if location tracking is not active. Its type can be changed using
+@samp{%define "location_type" "@var{class-name}".}
+@end deftypemethod
+
+@deftypemethod {Lexer} {int} yylex (@var{type1} @var{arg1}, ...)
+Return the next token. Its type is the return value, its semantic
+value and location are saved and returned by the ther methods in the
+interface. Invocations of @samp{%lex-param @{@var{type1}
+@var{arg1}@}} yield additional arguments.
+@end deftypemethod
+
+@deftypemethod {Lexer} {Position} getStartPos ()
+@deftypemethodx {Lexer} {Position} getEndPos ()
+Return respectively the first position of the last token that
+@code{yylex} returned, and the first position beyond it. These
+methods are not needed unless location tracking is active.
+
+The return type can be changed using @samp{%define "position_type"
+"@var{class-name}".}
+@end deftypemethod
+
+@deftypemethod {Lexer} {Object} getLVal ()
+Return respectively the first position of the last token that yylex
+returned, and the first position beyond it.
+
+The return type can be changed using @samp{%define "stype"
+"@var{class-name}".}
+@end deftypemethod
+
+
+If @code{%pure-parser} is not specified, the lexer interface
+resides in the same class (@code{YYParser}) as the Bison-generated
+parser. The fields and methods that are provided to
+this end are as follows.
+
+@deftypemethod {YYParser} {void} error (Location @var{l}, String @var{m})
+As explained in @pxref{Java Parser Interface}, this method is defined
+by the user to emit an error message. The first parameter is not used
+unless location tracking is active. Its type can be changed using
+@samp{%define "location_type" "@var{class-name}".}
+@end deftypemethod
+
+@deftypemethod {YYParser} {int} yylex (@var{type1} @var{arg1}, ...)
+Return the next token. Its type is the return value, its semantic
+value and location are saved into @code{yylval}, @code{yystartpos},
+@code{yyendpos}. Invocations of @samp{%lex-param @{@var{type1}
+@var{arg1}@}} yield additional arguments.
+@end deftypemethod
+
+@deftypecv {Field} {YYParser} Position yystartpos
+@deftypecvx {Field} {YYParser} Position yyendpos
+Contain respectively the first position of the last token that yylex
+returned, and the first position beyond it. These methods are not
+needed unless location tracking is active.
+
+The field's type can be changed using @samp{%define "position_type"
+"@var{class-name}".}
+@end deftypecv
+
+@deftypecv {Field} {YYParser} Object yylval
+Return respectively the first position of the last token that yylex
+returned, and the first position beyond it.
+
+The field's type can be changed using @samp{%define "stype"
+"@var{class-name}".}
+@end deftypecv
+
+@node Java Differences
+@subsection Differences between C/C++ and Java Grammars
+
+The different structure of the Java language forces several differences
+between C/C++ grammars, and grammars designed for Java parsers. This
+section summarizes these differences.
+
+@itemize
+@item
+Java lacks a preprocessor, so the @code{YYERROR}, @code{YYACCEPT},
+@code{YYABORT} symbols (@pxref{Table of Symbols}) cannot obviously be
+macros. Instead, they should be preceded by @code{return} when they
+appear in an action. The actual definition of these symbols is
+opaque to the Bison grammar, and it might change in the future. The
+only meaningful operation that you can do, is to return them.
+
+Note that of these three symbols, only @code{YYACCEPT} and
+@code{YYABORT} will cause a return from the @code{yyparse}
+method@footnote{Java parsers include the actions in a separate
+method than @code{yyparse} in order to have an intuitive syntax that
+corresponds to these C macros.}.
+
+@item
+The prolog declarations have a different meaning than in C/C++ code.
+@table @asis
+@item @code{%code imports}
+blocks are placed at the beginning of the Java source code. They may
+include copyright notices. For a @code{package} declarations, it is
+suggested to use @code{%define package} instead.
+
+@item unqualified @code{%code}
+blocks are placed inside the parser class.
+
+@item @code{%code lexer}
+blocks, if specified, should include the implementation of the
+scanner. If there is no such block, the scanner can be any class
+that implements the appropriate interface (see @pxref{Java Scanner
+Interface}).
+@end table
+
+Other @code{%code} blocks are not supported in Java parsers.
+The epilogue has the same meaning as in C/C++ code and it can
+be used to define other classes used by the parser.
+@end itemize
+
@c ================================================= FAQ
@node FAQ
* I can't build Bison:: Troubleshooting
* Where can I find help?:: Troubleshouting
* Bug Reports:: Troublereporting
-* Other Languages:: Parsers in Java and others
+* More Languages:: Parsers in C++, Java, and so on
* Beta Testing:: Experimenting development versions
* Mailing Lists:: Meeting other Bison users
@end menu
Send bug reports to @email{bug-bison@@gnu.org}.
-@node Other Languages
-@section Other Languages
+@node More Languages
+@section More Languages
@display
-Will Bison ever have C++ support? How about Java or @var{insert your
+Will Bison ever have C++ and Java support? How about @var{insert your
favorite language here}?
@end display
-C++ support is there now, and is documented. We'd love to add other
+C++ and Java support is there now, and is documented. We'd love to add other
languages; contributions are welcome.
@node Beta Testing
@xref{Rules, ,Syntax of Grammar Rules}.
@end deffn
-@deffn {Symbol} $accept
-The predefined nonterminal whose only rule is @samp{$accept: @var{start}
-$end}, where @var{start} is the start symbol. @xref{Start Decl, , The
-Start-Symbol}. It cannot be used in the grammar.
-@end deffn
+@deffn {Directive} <*>
+Used to define a default tagged @code{%destructor} or default tagged
+@code{%printer}.
-@deffn {Directive} %code @{@var{code}@}
-Specifies code to be inserted into the code file after the contents of the
-header file.
-@xref{Table of Symbols, ,%requires}.
-@end deffn
+This feature is experimental.
+More user feedback will help to determine whether it should become a permanent
+feature.
-@deffn {Directive} %provides @{@var{code}@}
-Specifies code to be inserted both into the header file (if generated;
-@pxref{Table of Symbols, ,%defines}) and into the code file after any
-Bison-generated definitions.
-@xref{Table of Symbols, ,%requires}.
+@xref{Destructor Decl, , Freeing Discarded Symbols}.
@end deffn
-@deffn {Directive} %requires @{@var{code}@}
-Specifies code to be inserted both into the header file (if generated;
-@pxref{Table of Symbols, ,%defines}) and into the code file before any
-Bison-generated definitions.
+@deffn {Directive} <>
+Used to define a default tagless @code{%destructor} or default tagless
+@code{%printer}.
-@cindex Prologue
-@findex %union
-@findex %provides
-@findex %code
-For example, the following declaration order in the grammar file reflects the
-order in which Bison will output these code blocks. However, you are free to
-declare these code blocks in your grammar file in whatever order is most
-convenient for you:
+This feature is experimental.
+More user feedback will help to determine whether it should become a permanent
+feature.
-@smallexample
-%requires @{
- /* Bison inserts this block into both the header file and the code
- * file. In both files, the point of insertion is before any
- * Bison-generated token, semantic type, location type, and class
- * definitions. This is a good place to define %union
- * dependencies, for example. */
-@}
-%union @{
- /* Unlike the traditional Yacc prologue blocks, the output order
- * for %requires, %provides or %code blocks is not affected by their
- * declaration position relative to any %union in the grammar file. */
-@}
-%provides @{
- /* Bison inserts this block into both the header file and the code
- * file. In both files, the point of insertion is after the
- * Bison-generated definitions. This is a good place to declare or
- * define public functions or data structures that depend on the
- * Bison-generated definitions. */
-@}
-%code @{
- /* Bison treats this block like a post-prologue block: it inserts
- * it into the code file after the contents of the header file. It
- * does *not* insert it into the header file. This is a good place
- * to declare or define internal functions or data structures that
- * depend on the Bison-generated definitions. */
-@}
-@end smallexample
+@xref{Destructor Decl, , Freeing Discarded Symbols}.
+@end deffn
-If you have multiple occurrences of any one of the above declarations, Bison
-will concatenate the contents in declaration order.
+@deffn {Symbol} $accept
+The predefined nonterminal whose only rule is @samp{$accept: @var{start}
+$end}, where @var{start} is the start symbol. @xref{Start Decl, , The
+Start-Symbol}. It cannot be used in the grammar.
+@end deffn
-@xref{Prologue, ,The Prologue}.
+@deffn {Directive} %code @{@var{code}@}
+@deffnx {Directive} %code @var{qualifier} @{@var{code}@}
+Insert @var{code} verbatim into output parser source.
+@xref{Decl Summary,,%code}.
@end deffn
@deffn {Directive} %debug
@end deffn
@end ifset
+@deffn {Directive} %define @var{define-variable}
+@deffnx {Directive} %define @var{define-variable} @var{value}
+Define a variable to adjust Bison's behavior.
+@xref{Decl Summary,,%define}.
+@end deffn
+
@deffn {Directive} %defines
Bison declaration to create a header file meant for the scanner.
@xref{Decl Summary}.
@end deffn
+@deffn {Directive} %defines @var{defines-file}
+Same as above, but save in the file @var{defines-file}.
+@xref{Decl Summary}.
+@end deffn
+
@deffn {Directive} %destructor
Specify how the parser should reclaim the memory associated to
discarded symbols. @xref{Destructor Decl, , Freeing Discarded Symbols}.
when @code{yyerror} is called.
@end deffn
-@deffn {Directive} %file-prefix="@var{prefix}"
+@deffn {Directive} %file-prefix "@var{prefix}"
Bison declaration to set the prefix of the output files. @xref{Decl
Summary}.
@end deffn
Run user code before parsing. @xref{Initial Action Decl, , Performing Actions before Parsing}.
@end deffn
+@deffn {Directive} %language
+Specify the programming language for the generated parser.
+@xref{Decl Summary}.
+@end deffn
+
@deffn {Directive} %left
Bison declaration to assign left associativity to token(s).
@xref{Precedence Decl, ,Operator Precedence}.
@xref{GLR Parsers, ,Writing @acronym{GLR} Parsers}.
@end deffn
-@deffn {Directive} %name-prefix="@var{prefix}"
+@deffn {Directive} %name-prefix "@var{prefix}"
Bison declaration to rename the external symbols. @xref{Decl Summary}.
@end deffn
@xref{Precedence Decl, ,Operator Precedence}.
@end deffn
-@deffn {Directive} %output="@var{file}"
+@deffn {Directive} %output "@var{file}"
Bison declaration to set the name of the parser file. @xref{Decl
Summary}.
@end deffn
@xref{Precedence Decl, ,Operator Precedence}.
@end deffn
+@deffn {Directive} %skeleton
+Specify the skeleton to use; usually for development.
+@xref{Decl Summary}.
+@end deffn
+
@deffn {Directive} %start
Bison declaration to specify the start symbol. @xref{Start Decl, ,The
Start-Symbol}.
@end deffn
-@deffn {Directive} %symbol-default
-Used to declare a default @code{%destructor} or default @code{%printer}.
-@xref{Destructor Decl, , Freeing Discarded Symbols}.
-@end deffn
-
@deffn {Directive} %token
Bison declaration to declare token(s) without specifying precedence.
@xref{Token Decl, ,Token Type Names}.
making @code{yyparse} return 1 immediately. The error reporting
function @code{yyerror} is not called. @xref{Parser Function, ,The
Parser Function @code{yyparse}}.
+
+For Java parsers, this functionality is invoked using @code{return YYABORT;}
+instead.
@end deffn
@deffn {Macro} YYACCEPT
Macro to pretend that a complete utterance of the language has been
read, by making @code{yyparse} return 0 immediately.
@xref{Parser Function, ,The Parser Function @code{yyparse}}.
+
+For Java parsers, this functionality is invoked using @code{return YYACCEPT;}
+instead.
@end deffn
@deffn {Macro} YYBACKUP
@code{yyerror} and then perform normal error recovery if possible
(@pxref{Error Recovery}), or (if recovery is impossible) make
@code{yyparse} return 1. @xref{Error Recovery}.
+
+For Java parsers, this functionality is invoked using @code{return YYERROR;}
+instead.
@end deffn
@deffn {Function} yyerror
@deffn {Variable} yynerrs
Global variable which Bison increments each time it reports a syntax error.
-(In a pure parser, it is a local variable within @code{yyparse}.)
+(In a pure parser, it is a local variable within @code{yyparse}. In a
+pure push parser, it is a member of yypstate.)
@xref{Error Reporting, ,The Error Reporting Function @code{yyerror}}.
@end deffn
parsing. @xref{Parser Function, ,The Parser Function @code{yyparse}}.
@end deffn
+@deffn {Function} yypstate_delete
+The function to delete a parser instance, produced by Bison in push mode;
+call this function to delete the memory associated with a parser.
+@xref{Parser Delete Function, ,The Parser Delete Function
+@code{yypstate_delete}}.
+@end deffn
+
+@deffn {Function} yypstate_new
+The function to create a parser instance, produced by Bison in push mode;
+call this function to create a new parser.
+@xref{Parser Create Function, ,The Parser Create Function
+@code{yypstate_new}}.
+@end deffn
+
+@deffn {Function} yypull_parse
+The parser function produced by Bison in push mode; call this function to
+parse the rest of the input stream.
+@xref{Pull Parser Function, ,The Pull Parser Function
+@code{yypull_parse}}.
+@end deffn
+
+@deffn {Function} yypush_parse
+The parser function produced by Bison in push mode; call this function to
+parse a single token. @xref{Push Parser Function, ,The Push Parser Function
+@code{yypush_parse}}.
+@end deffn
+
@deffn {Macro} YYPARSE_PARAM
An obsolete macro for specifying the name of a parameter that
@code{yyparse} should accept. The use of this macro is deprecated, and
@node Copying This Manual
@appendix Copying This Manual
-
-@menu
-* GNU Free Documentation License:: License for copying this manual.
-@end menu
-
@include fdl.texi
@node Index
@c LocalWords: pre STDC GNUC endif yy YY alloca lf stddef stdlib YYDEBUG
@c LocalWords: NUM exp subsubsection kbd Ctrl ctype EOF getchar isdigit
@c LocalWords: ungetc stdin scanf sc calc ulator ls lm cc NEG prec yyerrok
-@c LocalWords: longjmp fprintf stderr preg yylloc YYLTYPE cos ln
+@c LocalWords: longjmp fprintf stderr yylloc YYLTYPE cos ln
@c LocalWords: smallexample symrec val tptr FNCT fnctptr func struct sym
@c LocalWords: fnct putsym getsym fname arith fncts atan ptr malloc sizeof
@c LocalWords: strlen strcpy fctn strcmp isalpha symbuf realloc isalnum
@c LocalWords: ptypes itype YYPRINT trigraphs yytname expseq vindex dtype
-@c LocalWords: Rhs YYRHSLOC LE nonassoc op deffn typeless typefull yynerrs
+@c LocalWords: Rhs YYRHSLOC LE nonassoc op deffn typeless yynerrs
@c LocalWords: yychar yydebug msg YYNTOKENS YYNNTS YYNRULES YYNSTATES
@c LocalWords: cparse clex deftypefun NE defmac YYACCEPT YYABORT param
@c LocalWords: strncmp intval tindex lvalp locp llocp typealt YYBACKUP
@c LocalWords: hexflag STR exdent itemset asis DYYDEBUG YYFPRINTF args
@c LocalWords: infile ypp yxx outfile itemx tex leaderfill
@c LocalWords: hbox hss hfill tt ly yyin fopen fclose ofirst gcc ll
-@c LocalWords: yyrestart nbar yytext fst snd osplit ntwo strdup AST
+@c LocalWords: nbar yytext fst snd osplit ntwo strdup AST
@c LocalWords: YYSTACK DVI fdl printindex
projects / bison.git / blobdiff