@ifinfo
This file documents the Bison parser generator.
-Copyright (C) 1988, 1989, 1990, 1991, 1992, 1993, 1995, 1998, 1999, 2000
+Copyright (C) 1988, 1989, 1990, 1991, 1992, 1993, 1995, 1998, 1999,
+2000, 2001
Free Software Foundation, Inc.
Permission is granted to make and distribute verbatim copies of
@page
@vskip 0pt plus 1filll
Copyright @copyright{} 1988, 1989, 1990, 1991, 1992, 1993, 1995, 1998,
-1999, 2000
+1999, 2000, 2001
Free Software Foundation, Inc.
@sp 2
* Invocation:: How to run Bison (to produce the parser source file).
* Table of Symbols:: All the keywords of the Bison language are explained.
* Glossary:: Basic concepts are explained.
+* Copying This Manual:: License for copying this manual.
* Index:: Cross-references to the text.
--- The Detailed Node Listing ---
Reverse Polish Notation Calculator
-* Decls: Rpcalc Decls. Bison and C declarations for rpcalc.
+* Decls: Rpcalc Decls. Prologue (declarations) for rpcalc.
* Rules: Rpcalc Rules. Grammar Rules for rpcalc, with explanation.
* Lexer: Rpcalc Lexer. The lexical analyzer.
* Main: Rpcalc Main. The controlling function.
Outline of a Bison Grammar
-* C Declarations:: Syntax and usage of the C declarations section.
+* Prologue:: Syntax and usage of the prologue (declarations section).
* Bison Declarations:: Syntax and usage of the Bison declarations section.
* Grammar Rules:: Syntax and usage of the grammar rules section.
-* C Code:: Syntax and usage of the additional C code section.
+* Epilogue:: Syntax and usage of the epilogue (additional code section).
Defining Language Semantics
in alphabetical order by short options.
* Option Cross Key:: Alphabetical list of long options.
* VMS Invocation:: Bison command syntax on VMS.
+
+Copying This Manual
+
+* GNU Free Documentation License:: License for copying this manual.
+
@end menu
@node Introduction, Conditions, Top, Top
practical conditions for using Bison match the practical conditions for
using the other GNU tools.
-@node Copying, Concepts, Conditions, Top
-@unnumbered GNU GENERAL PUBLIC LICENSE
-@center Version 2, June 1991
-
-@display
-Copyright @copyright{} 1989, 1991 Free Software Foundation, Inc.
-59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
-
-Everyone is permitted to copy and distribute verbatim copies
-of this license document, but changing it is not allowed.
-@end display
-
-@unnumberedsec Preamble
-
- The licenses for most software are designed to take away your
-freedom to share and change it. By contrast, the GNU General Public
-License is intended to guarantee your freedom to share and change free
-software---to make sure the software is free for all its users. This
-General Public License applies to most of the Free Software
-Foundation's software and to any other program whose authors commit to
-using it. (Some other Free Software Foundation software is covered by
-the GNU Library General Public License instead.) You can apply it to
-your programs, too.
-
- When we speak of free software, we are referring to freedom, not
-price. Our General Public Licenses are designed to make sure that you
-have the freedom to distribute copies of free software (and charge for
-this service if you wish), that you receive source code or can get it
-if you want it, that you can change the software or use pieces of it
-in new free programs; and that you know you can do these things.
-
- To protect your rights, we need to make restrictions that forbid
-anyone to deny you these rights or to ask you to surrender the rights.
-These restrictions translate to certain responsibilities for you if you
-distribute copies of the software, or if you modify it.
-
- For example, if you distribute copies of such a program, whether
-gratis or for a fee, you must give the recipients all the rights that
-you have. You must make sure that they, too, receive or can get the
-source code. And you must show them these terms so they know their
-rights.
-
- We protect your rights with two steps: (1) copyright the software, and
-(2) offer you this license which gives you legal permission to copy,
-distribute and/or modify the software.
-
- Also, for each author's protection and ours, we want to make certain
-that everyone understands that there is no warranty for this free
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-want its recipients to know that what they have is not the original, so
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-patent must be licensed for everyone's free use or not licensed at all.
-
- The precise terms and conditions for copying, distribution and
-modification follow.
-
-@iftex
-@unnumberedsec TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION
-@end iftex
-@ifinfo
-@center TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION
-@end ifinfo
-
-@enumerate 0
-@item
-This License applies to any program or other work which contains
-a notice placed by the copyright holder saying it may be distributed
-under the terms of this General Public License. The ``Program'', below,
-refers to any such program or work, and a ``work based on the Program''
-means either the Program or any derivative work under copyright law:
-that is to say, a work containing the Program or a portion of it,
-either verbatim or with modifications and/or translated into another
-language. (Hereinafter, translation is included without limitation in
-the term ``modification''.) Each licensee is addressed as ``you''.
-
-Activities other than copying, distribution and modification are not
-covered by this License; they are outside its scope. The act of
-running the Program is not restricted, and the output from the Program
-is covered only if its contents constitute a work based on the
-Program (independent of having been made by running the Program).
-Whether that is true depends on what the Program does.
-
-@item
-You may copy and distribute verbatim copies of the Program's
-source code as you receive it, in any medium, provided that you
-conspicuously and appropriately publish on each copy an appropriate
-copyright notice and disclaimer of warranty; keep intact all the
-notices that refer to this License and to the absence of any warranty;
-and give any other recipients of the Program a copy of this License
-along with the Program.
-
-You may charge a fee for the physical act of transferring a copy, and
-you may at your option offer warranty protection in exchange for a fee.
-
-@item
-You may modify your copy or copies of the Program or any portion
-of it, thus forming a work based on the Program, and copy and
-distribute such modifications or work under the terms of Section 1
-above, provided that you also meet all of these conditions:
-
-@enumerate a
-@item
-You must cause the modified files to carry prominent notices
-stating that you changed the files and the date of any change.
-
-@item
-You must cause any work that you distribute or publish, that in
-whole or in part contains or is derived from the Program or any
-part thereof, to be licensed as a whole at no charge to all third
-parties under the terms of this License.
-
-@item
-If the modified program normally reads commands interactively
-when run, you must cause it, when started running for such
-interactive use in the most ordinary way, to print or display an
-announcement including an appropriate copyright notice and a
-notice that there is no warranty (or else, saying that you provide
-a warranty) and that users may redistribute the program under
-these conditions, and telling the user how to view a copy of this
-License. (Exception: if the Program itself is interactive but
-does not normally print such an announcement, your work based on
-the Program is not required to print an announcement.)
-@end enumerate
-
-These requirements apply to the modified work as a whole. If
-identifiable sections of that work are not derived from the Program,
-and can be reasonably considered independent and separate works in
-themselves, then this License, and its terms, do not apply to those
-sections when you distribute them as separate works. But when you
-distribute the same sections as part of a whole which is a work based
-on the Program, the distribution of the whole must be on the terms of
-this License, whose permissions for other licensees extend to the
-entire whole, and thus to each and every part regardless of who wrote it.
-
-Thus, it is not the intent of this section to claim rights or contest
-your rights to work written entirely by you; rather, the intent is to
-exercise the right to control the distribution of derivative or
-collective works based on the Program.
-
-In addition, mere aggregation of another work not based on the Program
-with the Program (or with a work based on the Program) on a volume of
-a storage or distribution medium does not bring the other work under
-the scope of this License.
-
-@item
-You may copy and distribute the Program (or a work based on it,
-under Section 2) in object code or executable form under the terms of
-Sections 1 and 2 above provided that you also do one of the following:
-
-@enumerate a
-@item
-Accompany it with the complete corresponding machine-readable
-source code, which must be distributed under the terms of Sections
-1 and 2 above on a medium customarily used for software interchange; or,
-
-@item
-Accompany it with a written offer, valid for at least three
-years, to give any third party, for a charge no more than your
-cost of physically performing source distribution, a complete
-machine-readable copy of the corresponding source code, to be
-distributed under the terms of Sections 1 and 2 above on a medium
-customarily used for software interchange; or,
-
-@item
-Accompany it with the information you received as to the offer
-to distribute corresponding source code. (This alternative is
-allowed only for noncommercial distribution and only if you
-received the program in object code or executable form with such
-an offer, in accord with Subsection b above.)
-@end enumerate
-
-The source code for a work means the preferred form of the work for
-making modifications to it. For an executable work, complete source
-code means all the source code for all modules it contains, plus any
-associated interface definition files, plus the scripts used to
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-special exception, the source code distributed need not include
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-form) with the major components (compiler, kernel, and so on) of the
-operating system on which the executable runs, unless that component
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-
-If distribution of executable or object code is made by offering
-access to copy from a designated place, then offering equivalent
-access to copy the source code from the same place counts as
-distribution of the source code, even though third parties are not
-compelled to copy the source along with the object code.
-
-@item
-You may not copy, modify, sublicense, or distribute the Program
-except as expressly provided under this License. Any attempt
-otherwise to copy, modify, sublicense or distribute the Program is
-void, and will automatically terminate your rights under this License.
-However, parties who have received copies, or rights, from you under
-this License will not have their licenses terminated so long as such
-parties remain in full compliance.
-
-@item
-You are not required to accept this License, since you have not
-signed it. However, nothing else grants you permission to modify or
-distribute the Program or its derivative works. These actions are
-prohibited by law if you do not accept this License. Therefore, by
-modifying or distributing the Program (or any work based on the
-Program), you indicate your acceptance of this License to do so, and
-all its terms and conditions for copying, distributing or modifying
-the Program or works based on it.
-
-@item
-Each time you redistribute the Program (or any work based on the
-Program), the recipient automatically receives a license from the
-original licensor to copy, distribute or modify the Program subject to
-these terms and conditions. You may not impose any further
-restrictions on the recipients' exercise of the rights granted herein.
-You are not responsible for enforcing compliance by third parties to
-this License.
-
-@item
-If, as a consequence of a court judgment or allegation of patent
-infringement or for any other reason (not limited to patent issues),
-conditions are imposed on you (whether by court order, agreement or
-otherwise) that contradict the conditions of this License, they do not
-excuse you from the conditions of this License. If you cannot
-distribute so as to satisfy simultaneously your obligations under this
-License and any other pertinent obligations, then as a consequence you
-may not distribute the Program at all. For example, if a patent
-license would not permit royalty-free redistribution of the Program by
-all those who receive copies directly or indirectly through you, then
-the only way you could satisfy both it and this License would be to
-refrain entirely from distribution of the Program.
-
-If any portion of this section is held invalid or unenforceable under
-any particular circumstance, the balance of the section is intended to
-apply and the section as a whole is intended to apply in other
-circumstances.
-
-It is not the purpose of this section to induce you to infringe any
-patents or other property right claims or to contest validity of any
-such claims; this section has the sole purpose of protecting the
-integrity of the free software distribution system, which is
-implemented by public license practices. Many people have made
-generous contributions to the wide range of software distributed
-through that system in reliance on consistent application of that
-system; it is up to the author/donor to decide if he or she is willing
-to distribute software through any other system and a licensee cannot
-impose that choice.
-
-This section is intended to make thoroughly clear what is believed to
-be a consequence of the rest of this License.
-
-@item
-If the distribution and/or use of the Program is restricted in
-certain countries either by patents or by copyrighted interfaces, the
-original copyright holder who places the Program under this License
-may add an explicit geographical distribution limitation excluding
-those countries, so that distribution is permitted only in or among
-countries not thus excluded. In such case, this License incorporates
-the limitation as if written in the body of this License.
-
-@item
-The Free Software Foundation may publish revised and/or new versions
-of the General Public License from time to time. Such new versions will
-be similar in spirit to the present version, but may differ in detail to
-address new problems or concerns.
-
-Each version is given a distinguishing version number. If the Program
-specifies a version number of this License which applies to it and ``any
-later version'', you have the option of following the terms and conditions
-either of that version or of any later version published by the Free
-Software Foundation. If the Program does not specify a version number of
-this License, you may choose any version ever published by the Free Software
-Foundation.
-
-@item
-If you wish to incorporate parts of the Program into other free
-programs whose distribution conditions are different, write to the author
-to ask for permission. For software which is copyrighted by the Free
-Software Foundation, write to the Free Software Foundation; we sometimes
-make exceptions for this. Our decision will be guided by the two goals
-of preserving the free status of all derivatives of our free software and
-of promoting the sharing and reuse of software generally.
-
-@iftex
-@heading NO WARRANTY
-@end iftex
-@ifinfo
-@center NO WARRANTY
-@end ifinfo
-
-@item
-BECAUSE THE PROGRAM IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY
-FOR THE PROGRAM, TO THE EXTENT PERMITTED BY APPLICABLE LAW. EXCEPT WHEN
-OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES
-PROVIDE THE PROGRAM ``AS IS'' WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED
-OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
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-TO THE QUALITY AND PERFORMANCE OF THE PROGRAM IS WITH YOU. SHOULD THE
-PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING,
-REPAIR OR CORRECTION.
-
-@item
-IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING
-WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY AND/OR
-REDISTRIBUTE THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES,
-INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING
-OUT OF THE USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED
-TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY
-YOU OR THIRD PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER
-PROGRAMS), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE
-POSSIBILITY OF SUCH DAMAGES.
-@end enumerate
-
-@iftex
-@heading END OF TERMS AND CONDITIONS
-@end iftex
-@ifinfo
-@center END OF TERMS AND CONDITIONS
-@end ifinfo
-
-@page
-@unnumberedsec How to Apply These Terms to Your New Programs
-
- If you develop a new program, and you want it to be of the greatest
-possible use to the public, the best way to achieve this is to make it
-free software which everyone can redistribute and change under these terms.
-
- To do so, attach the following notices to the program. It is safest
-to attach them to the start of each source file to most effectively
-convey the exclusion of warranty; and each file should have at least
-the ``copyright'' line and a pointer to where the full notice is found.
-
-@smallexample
-@var{one line to give the program's name and a brief idea of what it does.}
-Copyright (C) 19@var{yy} @var{name of author}
-
-This program is free software; you can redistribute it and/or modify
-it under the terms of the GNU General Public License as published by
-the Free Software Foundation; either version 2 of the License, or
-(at your option) any later version.
-
-This program is distributed in the hope that it will be useful,
-but WITHOUT ANY WARRANTY; without even the implied warranty of
-MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
-GNU General Public License for more details.
-
-You should have received a copy of the GNU General Public License
-along with this program; if not, write to the Free Software
-Foundation, Inc., 59 Temple Place - Suite 330,
-Boston, MA 02111-1307, USA.
-@end smallexample
-
-Also add information on how to contact you by electronic and paper mail.
-
-If the program is interactive, make it output a short notice like this
-when it starts in an interactive mode:
-
-@smallexample
-Gnomovision version 69, Copyright (C) 19@var{yy} @var{name of author}
-Gnomovision comes with ABSOLUTELY NO WARRANTY; for details
-type `show w'.
-This is free software, and you are welcome to redistribute it
-under certain conditions; type `show c' for details.
-@end smallexample
-
-The hypothetical commands @samp{show w} and @samp{show c} should show
-the appropriate parts of the General Public License. Of course, the
-commands you use may be called something other than @samp{show w} and
-@samp{show c}; they could even be mouse-clicks or menu items---whatever
-suits your program.
-
-You should also get your employer (if you work as a programmer) or your
-school, if any, to sign a ``copyright disclaimer'' for the program, if
-necessary. Here is a sample; alter the names:
-
-@smallexample
-Yoyodyne, Inc., hereby disclaims all copyright interest in the program
-`Gnomovision' (which makes passes at compilers) written by James Hacker.
-
-@var{signature of Ty Coon}, 1 April 1989
-Ty Coon, President of Vice
-@end smallexample
-
-This General Public License does not permit incorporating your program into
-proprietary programs. If your program is a subroutine library, you may
-consider it more useful to permit linking proprietary applications with the
-library. If this is what you want to do, use the GNU Library General
-Public License instead of this License.
+@include gpl.texi
@node Concepts, Examples, Copying, Top
@chapter The Concepts of Bison
a semantic value (the value of an integer,
the name of an identifier, etc.).
* Semantic Actions:: Each rule can have an action containing C code.
+* Locations Overview:: Tracking Locations.
* Bison Parser:: What are Bison's input and output,
how is the output used?
* Stages:: Stages in writing and running Bison grammars.
language, an expression typically has a semantic value that is a tree
structure describing the meaning of the expression.
-@node Semantic Actions, Bison Parser, Semantic Values, Concepts
+@node Semantic Actions, Locations Overview, Semantic Values, Concepts
@section Semantic Actions
@cindex semantic actions
@cindex actions, semantic
The action says how to produce the semantic value of the sum expression
from the values of the two subexpressions.
-@node Bison Parser, Stages, Semantic Actions, Concepts
+@node Locations Overview, Bison Parser, Semantic Actions, Concepts
+@section Locations
+@cindex location
+@cindex textual position
+@cindex position, textual
+
+Many applications, like interpreters or compilers, have to produce verbose
+and useful error messages. To achieve this, one must be able to keep track of
+the @dfn{textual position}, or @dfn{location}, of each syntactic construct.
+Bison provides a mechanism for handling these locations.
+
+Each token has a semantic value. In a similar fashion, each token has an
+associated location, but the type of locations is the same for all tokens and
+groupings. Moreover, the output parser is equipped with a default data
+structure for storing locations (@pxref{Locations}, for more details).
+
+Like semantic values, locations can be reached in actions using a dedicated
+set of constructs. In the example above, the location of the whole grouping
+is @code{@@$}, while the locations of the subexpressions are @code{@@1} and
+@code{@@3}.
+
+When a rule is matched, a default action is used to compute the semantic value
+of its left hand side (@pxref{Actions}). In the same way, another default
+action is used for locations. However, the action for locations is general
+enough for most cases, meaning there is usually no need to describe for each
+rule how @code{@@$} should be formed. When building a new location for a given
+grouping, the default behavior of the output parser is to take the beginning
+of the first symbol, and the end of the last symbol.
+
+@node Bison Parser, Stages, Locations Overview, Concepts
@section Bison Output: the Parser File
@cindex Bison parser
@cindex Bison utility
@example
%@{
-@var{C declarations}
+@var{Prologue (declarations)}
%@}
@var{Bison declarations}
%%
@var{Grammar rules}
%%
-@var{Additional C code}
+@var{Epilogue (additional code)}
@end example
@noindent
The @samp{%%}, @samp{%@{} and @samp{%@}} are punctuation that appears
in every Bison grammar file to separate the sections.
-The C declarations may define types and variables used in the actions.
-You can also use preprocessor commands to define macros used there, and use
+The prologue may define types and variables used in the actions. You can
+also use preprocessor commands to define macros used there, and use
@code{#include} to include header files that do any of these things.
The Bison declarations declare the names of the terminal and nonterminal
The grammar rules define how to construct each nonterminal symbol from its
parts.
-The additional C code can contain any C code you want to use. Often the
-definition of the lexical analyzer @code{yylex} goes here, plus subroutines
-called by the actions in the grammar rules. In a simple program, all the
-rest of the program can go here.
+The epilogue can contain any code you want to use. Often the definition of
+the lexical analyzer @code{yylex} goes here, plus subroutines called by the
+actions in the grammar rules. In a simple program, all the rest of the
+program can go here.
@node Examples, Grammar File, Concepts, Top
@chapter Examples
@samp{.y} extension is a convention used for Bison input files.
@menu
-* Decls: Rpcalc Decls. Bison and C declarations for rpcalc.
+* Decls: Rpcalc Decls. Prologue (declarations) for rpcalc.
* Rules: Rpcalc Rules. Grammar Rules for rpcalc, with explanation.
* Lexer: Rpcalc Lexer. The lexical analyzer.
* Main: Rpcalc Main. The controlling function.
%% /* Grammar rules and actions follow */
@end example
-The C declarations section (@pxref{C Declarations, ,The C Declarations Section}) contains two
+The declarations section (@pxref{Prologue, , The prologue}) contains two
preprocessor directives.
The @code{#define} directive defines the macro @code{YYSTYPE}, thus
arrange all the source code in one or more source files. For such a
simple example, the easiest thing is to put everything in one file. The
definitions of @code{yylex}, @code{yyerror} and @code{main} go at the
-end, in the ``additional C code'' section of the file (@pxref{Grammar
-Layout, ,The Overall Layout of a Bison Grammar}).
+end, in the epilogue of the file
+(@pxref{Grammar Layout, ,The Overall Layout of a Bison Grammar}).
For a large project, you would probably have several source files, and use
@code{make} to arrange to recompile them.
definition, which is kept in the header @file{calc.h}, is as follows. It
provides for either functions or variables to be placed in the table.
-@c FIXME: ANSIfy the prototypes for FNCTPTR etc.
@smallexample
@group
+/* Fonctions type. */
+typedef double (*func_t) (double);
+
/* Data type for links in the chain of symbols. */
struct symrec
@{
char *name; /* name of symbol */
int type; /* type of symbol: either VAR or FNCT */
- union @{
- double var; /* value of a VAR */
- double (*fnctptr)(); /* value of a FNCT */
+ union
+ @{
+ double var; /* value of a VAR */
+ func_t fnctptr; /* value of a FNCT */
@} value;
struct symrec *next; /* link field */
@};
/* The symbol table: a chain of `struct symrec'. */
extern symrec *sym_table;
-symrec *putsym ();
-symrec *getsym ();
+symrec *putsym (const char *, func_t);
+symrec *getsym (const char *);
@end group
@end smallexample
struct init
@{
char *fname;
- double (*fnct)();
+ double (*fnct)(double);
@};
@end group
@group
struct init arith_fncts[] =
@{
- "sin", sin,
- "cos", cos,
+ "sin", sin,
+ "cos", cos,
"atan", atan,
- "ln", log,
- "exp", exp,
+ "ln", log,
+ "exp", exp,
"sqrt", sqrt,
0, 0
@};
/* The symbol table: a chain of `struct symrec'. */
-symrec *sym_table = (symrec *)0;
+symrec *sym_table = (symrec *) 0;
@end group
@group
C-language function that recognizes correct instances of the grammar.
The Bison grammar input file conventionally has a name ending in @samp{.y}.
+@xref{Invocation, ,Invoking Bison}.
@menu
* Grammar Outline:: Overall layout of the grammar file.
* Rules:: How to write grammar rules.
* Recursion:: Writing recursive rules.
* Semantics:: Semantic values and actions.
+* Locations:: Locations and actions.
* Declarations:: All kinds of Bison declarations are described here.
* Multiple Parsers:: Putting more than one Bison parser in one program.
@end menu
@example
%@{
-@var{C declarations}
+@var{Prologue}
%@}
@var{Bison declarations}
@var{Grammar rules}
%%
-@var{Additional C code}
+@var{Epilogue}
@end example
Comments enclosed in @samp{/* @dots{} */} may appear in any of the sections.
@menu
-* C Declarations:: Syntax and usage of the C declarations section.
+* Prologue:: Syntax and usage of the prologue.
* Bison Declarations:: Syntax and usage of the Bison declarations section.
* Grammar Rules:: Syntax and usage of the grammar rules section.
-* C Code:: Syntax and usage of the additional C code section.
+* Epilogue:: Syntax and usage of the epilogue.
@end menu
-@node C Declarations, Bison Declarations, , Grammar Outline
-@subsection The C Declarations Section
-@cindex C declarations section
-@cindex declarations, C
+@node Prologue, Bison Declarations, , Grammar Outline
+@subsection The prologue
+@cindex declarations section
+@cindex Prologue
+@cindex declarations
-The @var{C declarations} section contains macro definitions and
+The @var{prologue} section contains macro definitions and
declarations of functions and variables that are used in the actions in the
grammar rules. These are copied to the beginning of the parser file so
that they precede the definition of @code{yyparse}. You can use
need any C declarations, you may omit the @samp{%@{} and @samp{%@}}
delimiters that bracket this section.
-@node Bison Declarations, Grammar Rules, C Declarations, Grammar Outline
+@node Bison Declarations, Grammar Rules, Prologue, Grammar Outline
@subsection The Bison Declarations Section
@cindex Bison declarations (introduction)
@cindex declarations, Bison (introduction)
In some simple grammars you may not need any declarations.
@xref{Declarations, ,Bison Declarations}.
-@node Grammar Rules, C Code, Bison Declarations, Grammar Outline
+@node Grammar Rules, Epilogue, Bison Declarations, Grammar Outline
@subsection The Grammar Rules Section
@cindex grammar rules section
@cindex rules section for grammar
@samp{%%} (which precedes the grammar rules) may never be omitted even
if it is the first thing in the file.
-@node C Code, , Grammar Rules, Grammar Outline
-@subsection The Additional C Code Section
+@node Epilogue, , Grammar Rules, Grammar Outline
+@subsection The epilogue
@cindex additional C code section
+@cindex epilogue
@cindex C code, section for additional
-The @var{additional C code} section is copied verbatim to the end of the
-parser file, just as the @var{C declarations} section is copied to the
-beginning. This is the most convenient place to put anything that you
-want to have in the parser file but which need not come before the
-definition of @code{yyparse}. For example, the definitions of
-@code{yylex} and @code{yyerror} often go here. @xref{Interface, ,Parser
-C-Language Interface}.
+The @var{epilogue} is copied verbatim to the end of the parser file, just as
+the @var{prologue} is copied to the beginning. This is the most convenient
+place to put anything that you want to have in the parser file but which need
+not come before the definition of @code{yyparse}. For example, the
+definitions of @code{yylex} and @code{yyerror} often go here.
+@xref{Interface, ,Parser C-Language Interface}.
If the last section is empty, you may omit the @samp{%%} that separates it
from the grammar rules.
The Bison parser itself contains many static variables whose names start
with @samp{yy} and many macros whose names start with @samp{YY}. It is a
good idea to avoid using any such names (except those documented in this
-manual) in the additional C code section of the grammar file.
+manual) in the epilogue of the grammar file.
@node Symbols, Rules, Grammar Outline, Grammar File
@section Symbols, Terminal and Nonterminal
defines two mutually-recursive nonterminals, since each refers to the
other.
-@node Semantics, Declarations, Recursion, Grammar File
+@node Semantics, Locations, Recursion, Grammar File
@section Defining Language Semantics
@cindex defining language semantics
@cindex language semantics, defining
@end example
@noindent
-This macro definition must go in the C declarations section of the grammar
-file (@pxref{Grammar Outline, ,Outline of a Bison Grammar}).
+This macro definition must go in the prologue of the grammar file
+(@pxref{Grammar Outline, ,Outline of a Bison Grammar}).
@node Multiple Types, Actions, Value Type, Semantics
@subsection More Than One Value Type
its value with an assignment to @code{$$}, and actions later in the rule
can refer to the value using @code{$@var{n}}. Since there is no symbol
to name the action, there is no way to declare a data type for the value
-in advance, so you must use the @samp{$<@dots{}>} construct to specify a
-data type each time you refer to this value.
+in advance, so you must use the @samp{$<@dots{}>@var{n}} construct to
+specify a data type each time you refer to this value.
There is no way to set the value of the entire rule with a mid-rule
action, because assignments to @code{$$} do not have that effect. The
converted to an end-of-rule action in this way, and this is what Bison
actually does to implement mid-rule actions.
-@node Declarations, Multiple Parsers, Semantics, Grammar File
+@node Locations, Declarations, Semantics, Grammar File
+@section Tracking Locations
+@cindex location
+@cindex textual position
+@cindex position, textual
+
+Though grammar rules and semantic actions are enough to write a fully
+functional parser, it can be useful to process some additionnal informations,
+especially symbol locations.
+
+@c (terminal or not) ?
+
+The way locations are handled is defined by providing a data type, and actions
+to take when rules are matched.
+
+@menu
+* Location Type:: Specifying a data type for locations.
+* Actions and Locations:: Using locations in actions.
+* Location Default Action:: Defining a general way to compute locations.
+@end menu
+
+@node Location Type, Actions and Locations, , Locations
+@subsection Data Type of Locations
+@cindex data type of locations
+@cindex default location type
+
+Defining a data type for locations is much simpler than for semantic values,
+since all tokens and groupings always use the same type.
+
+The type of locations is specified by defining a macro called @code{YYLTYPE}.
+When @code{YYLTYPE} is not defined, Bison uses a default structure type with
+four members:
+
+@example
+struct
+@{
+ int first_line;
+ int first_column;
+ int last_line;
+ int last_column;
+@}
+@end example
+
+@node Actions and Locations, Location Default Action, Location Type, Locations
+@subsection Actions and Locations
+@cindex location actions
+@cindex actions, location
+@vindex @@$
+@vindex @@@var{n}
+
+Actions are not only useful for defining language semantics, but also for
+describing the behavior of the output parser with locations.
+
+The most obvious way for building locations of syntactic groupings is very
+similar to the way semantic values are computed. In a given rule, several
+constructs can be used to access the locations of the elements being matched.
+The location of the @var{n}th component of the right hand side is
+@code{@@@var{n}}, while the location of the left hand side grouping is
+@code{@@$}.
+
+Here is a basic example using the default data type for locations:
+
+@example
+@group
+exp: @dots{}
+ | exp '/' exp
+ @{
+ @@$.first_column = @@1.first_column;
+ @@$.first_line = @@1.first_line;
+ @@$.last_column = @@3.last_column;
+ @@$.last_line = @@3.last_line;
+ if ($3)
+ $$ = $1 / $3;
+ else
+ @{
+ $$ = 1;
+ printf("Division by zero, l%d,c%d-l%d,c%d",
+ @@3.first_line, @@3.first_column,
+ @@3.last_line, @@3.last_column);
+ @}
+ @}
+@end group
+@end example
+
+As for semantic values, there is a default action for locations that is
+run each time a rule is matched. It sets the beginning of @code{@@$} to the
+beginning of the first symbol, and the end of @code{@@$} to the end of the
+last symbol.
+
+With this default action, the location tracking can be fully automatic. The
+example above simply rewrites this way:
+
+@example
+@group
+exp: @dots{}
+ | exp '/' exp
+ @{
+ if ($3)
+ $$ = $1 / $3;
+ else
+ @{
+ $$ = 1;
+ printf("Division by zero, l%d,c%d-l%d,c%d",
+ @@3.first_line, @@3.first_column,
+ @@3.last_line, @@3.last_column);
+ @}
+ @}
+@end group
+@end example
+
+@node Location Default Action, , Actions and Locations, Locations
+@subsection Default Action for Locations
+@vindex YYLLOC_DEFAULT
+
+Actually, actions are not the best place to compute locations. Since locations
+are much more general than semantic values, there is room in the output parser
+to redefine the default action to take for each rule. The
+@code{YYLLOC_DEFAULT} macro is called each time a rule is matched, before the
+associated action is run.
+
+Most of the time, this macro is general enough to suppress location
+dedicated code from semantic actions.
+
+The @code{YYLLOC_DEFAULT} macro takes three parameters. The first one is
+the location of the grouping (the result of the computation). The second one
+is an array holding locations of all right hand side elements of the rule
+being matched. The last one is the size of the right hand side rule.
+
+By default, it is defined this way:
+
+@example
+@group
+#define YYLLOC_DEFAULT(Current, Rhs, N) \
+ Current.last_line = Rhs[N].last_line; \
+ Current.last_column = Rhs[N].last_column;
+@end group
+@end example
+
+When defining @code{YYLLOC_DEFAULT}, you should consider that:
+
+@itemize @bullet
+@item
+All arguments are free of side-effects. However, only the first one (the
+result) should be modified by @code{YYLLOC_DEFAULT}.
+
+@item
+Before @code{YYLLOC_DEFAULT} is executed, the output parser sets @code{@@$}
+to @code{@@1}.
+
+@item
+For consistency with semantic actions, valid indexes for the location array
+range from 1 to @var{n}.
+@end itemize
+
+@node Declarations, Multiple Parsers, Locations, Grammar File
@section Bison Declarations
@cindex declarations, Bison
@cindex Bison declarations
be able to refer to token type codes and the variable
@code{yylval}. @xref{Token Values, ,Semantic Values of Tokens}.@refill
+@c @item %source_extension
+@c Specify the extension of the parser output file.
+@c
+@c For example, a grammar file named @file{foo.yy} and containing a
+@c @code{%source_extension .cpp} directive will produce a parser file
+@c named @file{foo.tab.cpp}
+@c
+@c @item %header_extension
+@c Specify the extension of the parser header file generated when
+@c @code{%define} or @samp{-d} are used.
+@c
+@c For example, a garmmar file named @file{foo.ypp} and containing a
+@c @code{%header_extension .hh} directive will produce a header file
+@c named @file{foo.tab.hh}
+
@item %verbose
Write an extra output file containing verbose descriptions of the
parser states and what is done for each type of look-ahead token in
called @file{foo.tab.c} by default. As a consequence, the verbose
output file is called @file{foo.output}.@refill
-@item %raw
-The output file @file{@var{name}.h} normally defines the tokens with
-Yacc-compatible token numbers. If this option is specified, the
-internal Bison numbers are used instead. (Yacc-compatible numbers start
-at 257 except for single-character tokens; Bison assigns token numbers
-sequentially for all tokens starting at 3.)
-
@item %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
Keep in mind that the parser uses many C identifiers starting with
@samp{yy} and @samp{YY} for internal purposes. If you use such an
-identifier (aside from those in this manual) in an action or in additional
-C code in the grammar file, you are likely to run into trouble.
+identifier (aside from those in this manual) in an action or in epilogue
+in the grammar file, you are likely to run into trouble.
@menu
* Parser Function:: How to call @code{yyparse} and what it returns.
@subsection Textual Positions of Tokens
@vindex yylloc
-If you are using the @samp{@@@var{n}}-feature (@pxref{Action Features,
-,Special Features for Use in Actions}) in actions to keep track of the
+If you are using the @samp{@@@var{n}}-feature (@pxref{Locations, ,
+Tracking Locations}) in actions to keep track of the
textual locations of tokens and groupings, then you must provide this
information in @code{yylex}. The function @code{yyparse} expects to
find the textual location of a token just parsed in the global variable
@code{yylloc}. So @code{yylex} must store the proper data in that
-variable. The value of @code{yylloc} is a structure and you need only
+variable.
+
+By default, the value of @code{yylloc} is a structure and you need only
initialize the members that are going to be used by the actions. The
four members are called @code{first_line}, @code{first_column},
@code{last_line} and @code{last_column}. Note that the use of this
errors. This is useful primarily in error rules.
@xref{Error Recovery}.
-@item @@@var{n}
-@findex @@@var{n}
-Acts like a structure variable containing information on the line
-numbers and column numbers of the @var{n}th component of the current
-rule. The structure has four members, like this:
+@item @@$
+@findex @@$
+Acts like a structure variable containing information on the textual position
+of the grouping made by the current rule. @xref{Locations, ,
+Tracking Locations}.
-@example
-struct @{
- int first_line, last_line;
- int first_column, last_column;
-@};
-@end example
+@c Check if those paragraphs are still useful or not.
-Thus, to get the starting line number of the third component, you would
-use @samp{@@3.first_line}.
+@c @example
+@c struct @{
+@c int first_line, last_line;
+@c int first_column, last_column;
+@c @};
+@c @end example
-In order for the members of this structure to contain valid information,
-you must make @code{yylex} supply this information about each token.
-If you need only certain members, then @code{yylex} need only fill in
-those members.
+@c Thus, to get the starting line number of the third component, you would
+@c use @samp{@@3.first_line}.
+
+@c In order for the members of this structure to contain valid information,
+@c you must make @code{yylex} supply this information about each token.
+@c If you need only certain members, then @code{yylex} need only fill in
+@c those members.
+
+@c The use of this feature makes the parser noticeably slower.
+
+@item @@@var{n}
+@findex @@@var{n}
+Acts like a structure variable containing information on the textual position
+of the @var{n}th component of the current rule. @xref{Locations, ,
+Tracking Locations}.
-The use of this feature makes the parser noticeably slower.
@end table
@node Algorithm, Error Recovery, Interface, Top
it is nonzero, all integers are parsed in hexadecimal, and tokens starting
with letters are parsed as integers if possible.
-The declaration of @code{hexflag} shown in the C declarations section of
-the parser file is needed to make it accessible to the actions
-(@pxref{C Declarations, ,The C Declarations Section}). You must also write the code in @code{yylex}
-to obey the flag.
+The declaration of @code{hexflag} shown in the prologue of the parser file
+is needed to make it accessible to the actions (@pxref{Prologue, ,The Prologue}).
+You must also write the code in @code{yylex} to obey the flag.
@node Tie-in Recovery, , Lexical Tie-ins, Context Dependency
@section Lexical Tie-ins and Error Recovery
runs, the @code{yydebug} parser-trace feature can help you figure out why.
To enable compilation of trace facilities, you must define the macro
-@code{YYDEBUG} when you compile the parser. You could use
-@samp{-DYYDEBUG=1} as a compiler option or you could put @samp{#define
-YYDEBUG 1} in the C declarations section of the grammar file
-(@pxref{C Declarations, ,The C Declarations Section}). Alternatively, use the @samp{-t} option when
-you run Bison (@pxref{Invocation, ,Invoking Bison}). We always define @code{YYDEBUG} so that
-debugging is always possible.
+@code{YYDEBUG} when you compile the parser. You could use @samp{-DYYDEBUG=1}
+as a compiler option or you could put @samp{#define YYDEBUG 1} in the prologue
+of the grammar file (@pxref{Prologue, , The Prologue}). Alternatively, use the
+@samp{-t} option when you run Bison (@pxref{Invocation, ,Invoking Bison}).
+We always define @code{YYDEBUG} so that debugging is always possible.
-The trace facility uses @code{stderr}, so you must add @w{@code{#include
-<stdio.h>}} to the C declarations section unless it is already there.
+The trace facility uses @code{stderr}, so you must add
+@w{@code{#include <stdio.h>}} to the prologue unless it is already there.
Once you have compiled the program with trace facilities, the way to
request a trace is to store a nonzero value in the variable @code{yydebug}.
@samp{.y}. The parser file's name is made by replacing the @samp{.y}
with @samp{.tab.c}. Thus, the @samp{bison foo.y} filename yields
@file{foo.tab.c}, and the @samp{bison hack/foo.y} filename yields
-@file{hack/foo.tab.c}.@refill
+@file{hack/foo.tab.c}. It's is also possible, in case you are writting
+C++ code instead of C in your grammar file, to name it @file{foo.ypp}
+or @file{foo.y++}. Then, the output files will take an extention like
+the given one as input (repectively @file{foo.tab.cpp} and @file{foo.tab.c++}).
+This feature takes effect with all options that manipulate filenames like
+@samp{-o} or @samp{-d}.
+
+For example :
+
+@example
+bison -d @var{infile.yxx}
+@end example
+@noindent
+will produce @file{infile.tab.cxx} and @file{infile.tab.hxx}. and
+
+@example
+bison -d @var{infile.y} -o @var{output.c++}
+@end example
+@noindent
+will produce @file{output.c++} and @file{outfile.h++}.
+
@menu
* Bison Options:: All the options described in detail,
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
Output a definition of the macro @code{YYDEBUG} into the parser file, so
@itemx --no-parser
Pretend that @code{%no_parser} was specified. @xref{Decl Summary}.
-@item -r
-@itemx --raw
-Pretend that @code{%raw} was specified. @xref{Decl Summary}.
-
@item -k
@itemx --token-table
Pretend that @code{%token_table} was specified. @xref{Decl Summary}.
\line{ --no-lines \leaderfill -l}
\line{ --no-parser \leaderfill -n}
\line{ --output-file \leaderfill -o}
-\line{ --raw \leaderfill -r}
\line{ --token-table \leaderfill -k}
\line{ --verbose \leaderfill -v}
\line{ --version \leaderfill -V}
--no-lines -l
--no-parser -n
--output-file=@var{outfile} -o @var{outfile}
---raw -r
--token-table -k
--verbose -v
--version -V
@item YYLTYPE
Macro for the data type of @code{yylloc}; a structure with four
-members. @xref{Token Positions, ,Textual Positions of Tokens}.
+members. @xref{Location Type, , Data Types of Locations}.
@item yyltype
Default value for YYLTYPE.
Macro whose value indicates whether the parser is recovering from a
syntax error. @xref{Action Features, ,Special Features for Use in Actions}.
+@item YYSTACK_USE_ALLOCA
+Macro used to control the use of @code{alloca}. If defined to @samp{0},
+the parser will not use @code{alloca} but @code{malloc} when trying to
+grow its internal stacks. Do @emph{not} define @code{YYSTACK_USE_ALLOCA}
+to anything else.
+
@item YYSTYPE
Macro for the data type of semantic values; @code{int} by default.
@xref{Value Type, ,Data Types of Semantic Values}.
Bison declaration to create a header file meant for the scanner.
@xref{Decl Summary}.
+@c @item %source_extension
+@c Bison declaration to specify the generated parser output file extension.
+@c @xref{Decl Summary}.
+@c
+@c @item %header_extension
+@c Bison declaration to specify the generated parser header file extension
+@c if required. @xref{Decl Summary}.
+
@item %left
Bison declaration to assign left associativity to token(s).
@xref{Precedence Decl, ,Operator Precedence}.
Bison declaration to request a pure (reentrant) parser.
@xref{Pure Decl, ,A Pure (Reentrant) Parser}.
-@item %raw
-Bison declaration to use Bison internal token code numbers in token
-tables instead of the usual Yacc-compatible token code numbers.
-@xref{Decl Summary}.
-
@item %right
Bison declaration to assign right associativity to token(s).
@xref{Precedence Decl, ,Operator Precedence}.
@table @samp
@item %%
Delimiter used to separate the grammar rule section from the
-Bison declarations section or the additional C code section.
+Bison declarations section or the epilogue.
@xref{Grammar Layout, ,The Overall Layout of a Bison Grammar}.
@item %@{ %@}
All code listed between @samp{%@{} and @samp{%@}} is copied directly to
-the output file uninterpreted. Such code forms the ``C declarations''
-section of the input file. @xref{Grammar Outline, ,Outline of a Bison
+the output file uninterpreted. Such code forms the prologue of the input
+file. @xref{Grammar Outline, ,Outline of a Bison
Grammar}.
@item /*@dots{}*/
@xref{Rules, ,Syntax of Grammar Rules}.
@end table
-@node Glossary, Index, Table of Symbols, Top
+@node Glossary, Copying This Manual, Table of Symbols, Top
@appendix Glossary
@cindex glossary
@xref{Language and Grammar, ,Languages and Context-Free Grammars}.
@end table
-@node Index, , Glossary, Top
+@node Copying This Manual, Index, Glossary, Top
+@appendix Copying This Manual
+
+@menu
+* GNU Free Documentation License:: License for copying this manual.
+@end menu
+
+@include fdl.texi
+
+@node Index, , Copying This Manual, Top
@unnumbered Index
@printindex cp
projects / bison.git / blobdiff