When a literal string is used to define two different tokens,

[bison.git] / doc / bison.texinfo

diff --git a/doc/bison.texinfo b/doc/bison.texinfo
index c7fa40b409e52602602a650f4e9eb99e3c4e3bd9..3cf61b01dc303a702b47714cd5fb3583c09bcc7f 100644 (file)
--- a/doc/bison.texinfo
+++ b/doc/bison.texinfo
@@ -1,20 +1,19 @@
 \input texinfo @c -*-texinfo-*-
 @comment %**start of header
 @setfilename bison.info
 \input texinfo @c -*-texinfo-*-
 @comment %**start of header
 @setfilename bison.info

-@settitle Bison 1.25
+@include version.texi
+@settitle Bison @value{VERSION}

 @setchapternewpage odd
 
 @iftex
 @finalout
 @end iftex
 
 @setchapternewpage odd
 
 @iftex
 @finalout
 @end iftex
 

-@c SMALL BOOK version   
+@c SMALL BOOK version

 @c This edition has been formatted so that you can format and print it in
 @c This edition has been formatted so that you can format and print it in

-@c the smallbook format. 
+@c the smallbook format.

 @c @smallbook
 
 @c @smallbook
 

-@c next time, consider using @set for edition number, etc...
-

 @c Set following if you have the new `shorttitlepage' command
 @c @clear shorttitlepage-enabled
 @c @set shorttitlepage-enabled
 @c Set following if you have the new `shorttitlepage' command
 @c @clear shorttitlepage-enabled
 @c @set shorttitlepage-enabled


@@ -36,10 +35,19 @@
 @end ifinfo
 @comment %**end of header
 
 @end ifinfo
 @comment %**end of header
 

+@ifinfo
+@format
+START-INFO-DIR-ENTRY
+* bison: (bison).      GNU Project parser generator (yacc replacement).
+END-INFO-DIR-ENTRY
+@end format
+@end ifinfo
+

 @ifinfo
 This file documents the Bison parser generator.
 
 @ifinfo
 This file documents the Bison parser generator.
 

-Copyright (C) 1988, 89, 90, 91, 92, 93, 1995 Free Software Foundation, Inc.
+Copyright (C) 1988, 1989, 1990, 1991, 1992, 1993, 1995, 1998, 1999, 2000
+Free Software Foundation, Inc.

 
 Permission is granted to make and distribute verbatim copies of
 this manual provided the copyright notice and this permission notice
 
 Permission is granted to make and distribute verbatim copies of
 this manual provided the copyright notice and this permission notice


@@ -73,21 +81,22 @@ instead of in the original English.
 @titlepage
 @title Bison
 @subtitle The YACC-compatible Parser Generator
 @titlepage
 @title Bison
 @subtitle The YACC-compatible Parser Generator

-@subtitle August 1995, Bison Version 1.25
+@subtitle @value{UPDATED}, Bison Version @value{VERSION}

 
 @author by Charles Donnelly and Richard Stallman
 
 @page
 @vskip 0pt plus 1filll
 
 @author by Charles Donnelly and Richard Stallman
 
 @page
 @vskip 0pt plus 1filll

-Copyright @copyright{} 1988, 89, 90, 91, 92, 93, 1995 Free Software
-Foundation 
+Copyright @copyright{} 1988, 1989, 1990, 1991, 1992, 1993, 1995, 1998,
+1999, 2000
+Free Software Foundation, Inc.

 
 @sp 2
 Published by the Free Software Foundation @*
 59 Temple Place, Suite 330 @*
 Boston, MA  02111-1307  USA @*
 
 @sp 2
 Published by the Free Software Foundation @*
 59 Temple Place, Suite 330 @*
 Boston, MA  02111-1307  USA @*

-Printed copies are available for $15 each.@*
-ISBN 1-882114-45-0
+Printed copies are available from the Free Software Foundation.@*
+ISBN 1-882114-44-2

 
 Permission is granted to make and distribute verbatim copies of
 this manual provided the copyright notice and this permission notice
 
 Permission is granted to make and distribute verbatim copies of
 this manual provided the copyright notice and this permission notice


@@ -116,17 +125,18 @@ instead of in the original English.
 @sp 2
 Cover art by Etienne Suvasa.
 @end titlepage
 @sp 2
 Cover art by Etienne Suvasa.
 @end titlepage

-@page
+
+@contents

 
 @node Top, Introduction, (dir), (dir)
 
 @ifinfo
 
 @node Top, Introduction, (dir), (dir)
 
 @ifinfo

-This manual documents version 1.25 of Bison.
+This manual documents version @value{VERSION} of Bison.

 @end ifinfo
 
 @menu
 @end ifinfo
 
 @menu

-* Introduction::      
-* Conditions::        
+* Introduction::
+* Conditions::

 * Copying::           The GNU General Public License says
                         how you can copy and share Bison
 
 * Copying::           The GNU General Public License says
                         how you can copy and share Bison
 


@@ -186,9 +196,9 @@ Reverse Polish Notation Calculator
 
 Grammar Rules for @code{rpcalc}
 
 
 Grammar Rules for @code{rpcalc}
 

-* Rpcalc Input::      
-* Rpcalc Line::       
-* Rpcalc Expr::       
+* Rpcalc Input::
+* Rpcalc Line::
+* Rpcalc Expr::

 
 Multi-Function Calculator: @code{mfcalc}
 
 
 Multi-Function Calculator: @code{mfcalc}
 


@@ -237,7 +247,7 @@ Bison Declarations
 Parser C-Language Interface
 
 * Parser Function::   How to call @code{yyparse} and what it returns.
 Parser C-Language Interface
 
 * Parser Function::   How to call @code{yyparse} and what it returns.

-* Lexical::           You must supply a function @code{yylex} 
+* Lexical::           You must supply a function @code{yylex}

                         which reads tokens.
 * Error Reporting::   You must supply a function @code{yyerror}.
 * Action Features::   Special features for use in actions.
                         which reads tokens.
 * Error Reporting::   You must supply a function @code{yyerror}.
 * Action Features::   Special features for use in actions.


@@ -253,7 +263,7 @@ The Lexical Analyzer Function @code{yylex}
 * Pure Calling::      How the calling convention differs
                         in a pure parser (@pxref{Pure Decl, ,A Pure (Reentrant) Parser}).
 
 * Pure Calling::      How the calling convention differs
                         in a pure parser (@pxref{Pure Decl, ,A Pure (Reentrant) Parser}).
 

-The Bison Parser Algorithm 
+The Bison Parser Algorithm

 
 * Look-Ahead::        Parser looks one token ahead when deciding what to do.
 * Shift/Reduce::      Conflicts: when either shifting or reduction is valid.
 
 * Look-Ahead::        Parser looks one token ahead when deciding what to do.
 * Shift/Reduce::      Conflicts: when either shifting or reduction is valid.


@@ -280,7 +290,7 @@ Handling Context Dependencies
 
 Invoking Bison
 
 
 Invoking Bison
 

-* Bison Options::     All the options described in detail, 
+* Bison Options::     All the options described in detail,

                        in alphabetical order by short options.
 * Option Cross Key::  Alphabetical list of long options.
 * VMS Invocation::    Bison command syntax on VMS.
                        in alphabetical order by short options.
 * Option Cross Key::  Alphabetical list of long options.
 * VMS Invocation::    Bison command syntax on VMS.


@@ -310,18 +320,18 @@ Bison was written primarily by Robert Corbett; Richard Stallman made it
 Yacc-compatible.  Wilfred Hansen of Carnegie Mellon University added
 multicharacter string literals and other features.
 
 Yacc-compatible.  Wilfred Hansen of Carnegie Mellon University added
 multicharacter string literals and other features.
 

-This edition corresponds to version 1.25 of Bison.
+This edition corresponds to version @value{VERSION} of Bison.

 
 @node Conditions, Copying, Introduction, Top
 @unnumbered Conditions for Using Bison
 
 As of Bison version 1.24, we have changed the distribution terms for
 
 @node Conditions, Copying, Introduction, Top
 @unnumbered Conditions for Using Bison
 
 As of Bison version 1.24, we have changed the distribution terms for

-@code{yyparse} to permit using Bison's output in non-free programs.
+@code{yyparse} to permit using Bison's output in nonfree programs.

 Formerly, Bison parsers could be used only in programs that were free
 software.
 
 The other GNU programming tools, such as the GNU C compiler, have never
 Formerly, Bison parsers could be used only in programs that were free
 software.
 
 The other GNU programming tools, such as the GNU C compiler, have never

-had such a requirement.  They could always be used for non-free
+had such a requirement.  They could always be used for nonfree

 software.  The reason Bison was different was not due to a special
 policy decision; it resulted from applying the usual General Public
 License to all of the Bison source code.
 software.  The reason Bison was different was not due to a special
 policy decision; it resulted from applying the usual General Public
 License to all of the Bison source code.


@@ -346,7 +356,7 @@ using the other GNU tools.
 
 @display
 Copyright @copyright{} 1989, 1991 Free Software Foundation, Inc.
 
 @display
 Copyright @copyright{} 1989, 1991 Free Software Foundation, Inc.

-675 Mass Ave, Cambridge, MA 02139, USA
+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.
 
 Everyone is permitted to copy and distribute verbatim copies
 of this license document, but changing it is not allowed.


@@ -692,7 +702,8 @@ 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
 
 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., 675 Mass Ave, Cambridge, MA 02139, USA.
+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.
 @end smallexample
 
 Also add information on how to contact you by electronic and paper mail.


@@ -702,7 +713,7 @@ when it starts in an interactive mode:
 
 @smallexample
 Gnomovision version 69, Copyright (C) 19@var{yy} @var{name of author}
 
 @smallexample
 Gnomovision version 69, Copyright (C) 19@var{yy} @var{name of author}

-Gnomovision comes with ABSOLUTELY NO WARRANTY; for details 
+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.
 type `show w'.
 This is free software, and you are welcome to redistribute it
 under certain conditions; type `show c' for details.


@@ -959,7 +970,7 @@ also produce some output based on the input.  In a Bison grammar, a grammar
 rule can have an @dfn{action} made up of C statements.  Each time the
 parser recognizes a match for that rule, the action is executed.
 @xref{Actions}.
 rule can have an @dfn{action} made up of C statements.  Each time the
 parser recognizes a match for that rule, the action is executed.
 @xref{Actions}.

-        
+

 Most of the time, the purpose of an action is to compute the semantic value
 of the whole construct from the semantic values of its parts.  For example,
 suppose we have a rule which says an expression can be the sum of two
 Most of the time, the purpose of an action is to compute the semantic value
 of the whole construct from the semantic values of its parts.  For example,
 suppose we have a rule which says an expression can be the sum of two


@@ -1250,9 +1261,9 @@ main job of most actions.  The semantic values of the components of the
 rule are referred to as @code{$1}, @code{$2}, and so on.
 
 @menu
 rule are referred to as @code{$1}, @code{$2}, and so on.
 
 @menu

-* Rpcalc Input::      
-* Rpcalc Line::       
-* Rpcalc Expr::       
+* Rpcalc Input::
+* Rpcalc Line::
+* Rpcalc Expr::

 @end menu
 
 @node Rpcalc Input, Rpcalc Line,  , Rpcalc Rules
 @end menu
 
 @node Rpcalc Input, Rpcalc Line,  , Rpcalc Rules


@@ -1411,7 +1422,7 @@ Here is the code for the lexical analyzer:
 
 @example
 @group
 
 @example
 @group

-/* Lexical analyzer returns a double floating point 
+/* Lexical analyzer returns a double floating point

    number on the stack and the token NUM, or the ASCII
    character read if not a number.  Skips all blanks
    and tabs, returns 0 for EOF. */
    number on the stack and the token NUM, or the ASCII
    character read if not a number.  Skips all blanks
    and tabs, returns 0 for EOF. */


@@ -1420,17 +1431,18 @@ Here is the code for the lexical analyzer:
 @end group
 
 @group
 @end group
 
 @group

-yylex ()
+int
+yylex (void)

 @{
   int c;
 
   /* skip white space  */
 @{
   int c;
 
   /* skip white space  */

-  while ((c = getchar ()) == ' ' || c == '\t')  
+  while ((c = getchar ()) == ' ' || c == '\t')

     ;
 @end group
 @group
   /* process numbers   */
     ;
 @end group
 @group
   /* process numbers   */

-  if (c == '.' || isdigit (c))                
+  if (c == '.' || isdigit (c))

     @{
       ungetc (c, stdin);
       scanf ("%lf", &yylval);
     @{
       ungetc (c, stdin);
       scanf ("%lf", &yylval);


@@ -1439,10 +1451,10 @@ yylex ()
 @end group
 @group
   /* return end-of-file  */
 @end group
 @group
   /* return end-of-file  */

-  if (c == EOF)                            
+  if (c == EOF)

     return 0;
   /* return single chars */
     return 0;
   /* return single chars */

-  return c;                                
+  return c;

 @}
 @end group
 @end example
 @}
 @end group
 @end example


@@ -1458,9 +1470,10 @@ kept to the bare minimum.  The only requirement is that it call
 
 @example
 @group
 
 @example
 @group

-main ()
+int
+main (void)

 @{
 @{

-  yyparse ();
+  return yyparse ();

 @}
 @end group
 @end example
 @}
 @end group
 @end example


@@ -1470,16 +1483,17 @@ main ()
 @cindex error reporting routine
 
 When @code{yyparse} detects a syntax error, it calls the error reporting
 @cindex error reporting routine
 
 When @code{yyparse} detects a syntax error, it calls the error reporting

-function @code{yyerror} to print an error message (usually but not always
-@code{"parse error"}).  It is up to the programmer to supply @code{yyerror}
-(@pxref{Interface, ,Parser C-Language Interface}), so here is the definition we will use:
+function @code{yyerror} to print an error message (usually but not
+always @code{"parse error"}).  It is up to the programmer to supply
+@code{yyerror} (@pxref{Interface, ,Parser C-Language Interface}), so
+here is the definition we will use:

 
 @example
 @group
 #include <stdio.h>
 
 
 @example
 @group
 #include <stdio.h>
 

-yyerror (s)  /* Called by yyparse on error */
-     char *s;
+void
+yyerror (const char *s)  /* Called by yyparse on error */

 @{
   printf ("%s\n", s);
 @}
 @{
   printf ("%s\n", s);
 @}


@@ -1491,17 +1505,18 @@ and continue parsing if the grammar contains a suitable error rule
 (@pxref{Error Recovery}).  Otherwise, @code{yyparse} returns nonzero.  We
 have not written any error rules in this example, so any invalid input will
 cause the calculator program to exit.  This is not clean behavior for a
 (@pxref{Error Recovery}).  Otherwise, @code{yyparse} returns nonzero.  We
 have not written any error rules in this example, so any invalid input will
 cause the calculator program to exit.  This is not clean behavior for a

-real calculator, but it is adequate in the first example.
+real calculator, but it is adequate for the first example.

 
 @node Rpcalc Gen, Rpcalc Compile, Rpcalc Error, RPN Calc
 @subsection Running Bison to Make the Parser
 @cindex running Bison (introduction)
 
 
 @node Rpcalc Gen, Rpcalc Compile, Rpcalc Error, RPN Calc
 @subsection Running Bison to Make the Parser
 @cindex running Bison (introduction)
 

-Before running Bison to produce a parser, we need to decide how to 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}).
+Before running Bison to produce a parser, we need to decide how to
+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}).

 
 For a large project, you would probably have several source files, and use
 @code{make} to arrange to recompile them.
 
 For a large project, you would probably have several source files, and use
 @code{make} to arrange to recompile them.


@@ -1615,8 +1630,8 @@ exp:      NUM                @{ $$ = $1;         @}
 @end example
 
 @noindent
 @end example
 
 @noindent

-The functions @code{yylex}, @code{yyerror} and @code{main} can be the same
-as before.
+The functions @code{yylex}, @code{yyerror} and @code{main} can be the
+same as before.

 
 There are two important new features shown in this code.
 
 
 There are two important new features shown in this code.
 


@@ -1658,10 +1673,10 @@ Here is a sample run of @file{calc.y}:
 
 Up to this point, this manual has not addressed the issue of @dfn{error
 recovery}---how to continue parsing after the parser detects a syntax
 
 Up to this point, this manual has not addressed the issue of @dfn{error
 recovery}---how to continue parsing after the parser detects a syntax

-error.  All we have handled is error reporting with @code{yyerror}.  Recall
-that by default @code{yyparse} returns after calling @code{yyerror}.  This
-means that an erroneous input line causes the calculator program to exit.
-Now we show how to rectify this deficiency.
+error.  All we have handled is error reporting with @code{yyerror}.
+Recall that by default @code{yyparse} returns after calling
+@code{yyerror}.  This means that an erroneous input line causes the
+calculator program to exit.  Now we show how to rectify this deficiency.

 
 The Bison language itself includes the reserved word @code{error}, which
 may be included in the grammar rules.  In the example below it has
 
 The Bison language itself includes the reserved word @code{error}, which
 may be included in the grammar rules.  In the example below it has


@@ -1676,14 +1691,15 @@ line:     '\n'
 @end group
 @end example
 
 @end group
 @end example
 

-This addition to the grammar allows for simple error recovery in the event
-of a parse error.  If an expression that cannot be evaluated is read, the
-error will be recognized by the third rule for @code{line}, and parsing
-will continue.  (The @code{yyerror} function is still called upon to print
-its message as well.)  The action executes the statement @code{yyerrok}, a
-macro defined automatically by Bison; its meaning is that error recovery is
-complete (@pxref{Error Recovery}).  Note the difference between
-@code{yyerrok} and @code{yyerror}; neither one is a misprint.@refill
+This addition to the grammar allows for simple error recovery in the
+event of a parse error.  If an expression that cannot be evaluated is
+read, the error will be recognized by the third rule for @code{line},
+and parsing will continue.  (The @code{yyerror} function is still called
+upon to print its message as well.)  The action executes the statement
+@code{yyerrok}, a macro defined automatically by Bison; its meaning is
+that error recovery is complete (@pxref{Error Recovery}).  Note the
+difference between @code{yyerrok} and @code{yyerror}; neither one is a
+misprint.@refill

 
 This form of error recovery deals with syntax errors.  There are other
 kinds of errors; for example, division by zero, which raises an exception
 
 This form of error recovery deals with syntax errors.  There are other
 kinds of errors; for example, division by zero, which raises an exception


@@ -1707,7 +1723,7 @@ as @code{sin}, @code{cos}, etc.
 
 It is easy to add new operators to the infix calculator as long as they are
 only single-character literals.  The lexical analyzer @code{yylex} passes
 
 It is easy to add new operators to the infix calculator as long as they are
 only single-character literals.  The lexical analyzer @code{yylex} passes

-back all non-number characters as tokens, so new grammar rules suffice for
+back all nonnumber characters as tokens, so new grammar rules suffice for

 adding a new operator.  But we want something more flexible: built-in
 functions whose syntax has this form:
 
 adding a new operator.  But we want something more flexible: built-in
 functions whose syntax has this form:
 


@@ -1843,6 +1859,7 @@ The symbol table itself consists of a linked list of records.  Its
 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.
 
 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
 /* Data type for links in the chain of symbols.      */
 @smallexample
 @group
 /* Data type for links in the chain of symbols.      */


@@ -1877,16 +1894,17 @@ function that initializes the symbol table.  Here it is, and
 @group
 #include <stdio.h>
 
 @group
 #include <stdio.h>
 

-main ()
+int
+main (void)

 @{
   init_table ();
 @{
   init_table ();

-  yyparse ();
+  return yyparse ();

 @}
 @end group
 
 @group
 @}
 @end group
 
 @group

-yyerror (s)  /* Called by yyparse on error */
-     char *s;
+void
+yyerror (const char *s)  /* Called by yyparse on error */

 @{
   printf ("%s\n", s);
 @}
 @{
   printf ("%s\n", s);
 @}


@@ -1899,23 +1917,25 @@ struct init
 @end group
 
 @group
 @end group
 
 @group

-struct init arith_fncts[]
-  = @{
-      "sin", sin,
-      "cos", cos,
-      "atan", atan,
-      "ln", log,
-      "exp", exp,
-      "sqrt", sqrt,
-      0, 0
-    @};
+struct init arith_fncts[] =
+@{
+  "sin", sin,
+  "cos", cos,
+  "atan", atan,
+  "ln", log,
+  "exp", exp,
+  "sqrt", sqrt,
+  0, 0
+@};

 
 /* The symbol table: a chain of `struct symrec'.  */
 symrec *sym_table = (symrec *)0;
 @end group
 
 @group
 
 /* The symbol table: a chain of `struct symrec'.  */
 symrec *sym_table = (symrec *)0;
 @end group
 
 @group

-init_table ()  /* puts arithmetic functions in table. */
+/* Put arithmetic functions in table. */
+void
+init_table (void)

 @{
   int i;
   symrec *ptr;
 @{
   int i;
   symrec *ptr;


@@ -1940,9 +1960,7 @@ found, a pointer to that symbol is returned; otherwise zero is returned.
 
 @smallexample
 symrec *
 
 @smallexample
 symrec *

-putsym (sym_name,sym_type)
-     char *sym_name;
-     int sym_type;
+putsym (char *sym_name, int sym_type)

 @{
   symrec *ptr;
   ptr = (symrec *) malloc (sizeof (symrec));
 @{
   symrec *ptr;
   ptr = (symrec *) malloc (sizeof (symrec));


@@ -1956,8 +1974,7 @@ putsym (sym_name,sym_type)
 @}
 
 symrec *
 @}
 
 symrec *

-getsym (sym_name)
-     char *sym_name;
+getsym (const char *sym_name)

 @{
   symrec *ptr;
   for (ptr = sym_table; ptr != (symrec *) 0;
 @{
   symrec *ptr;
   for (ptr = sym_table; ptr != (symrec *) 0;


@@ -1986,7 +2003,9 @@ operators in @code{yylex}.
 @smallexample
 @group
 #include <ctype.h>
 @smallexample
 @group
 #include <ctype.h>

-yylex ()
+
+int
+yylex (void)

 @{
   int c;
 
 @{
   int c;
 


@@ -2170,12 +2189,13 @@ if it is the first thing in the file.
 @cindex additional C code section
 @cindex C code, section for additional
 
 @cindex additional C code section
 @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{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}.

 
 If the last section is empty, you may omit the @samp{%%} that separates it
 from the grammar rules.
 
 If the last section is empty, you may omit the @samp{%%} that separates it
 from the grammar rules.


@@ -2246,7 +2266,7 @@ for @code{yylex}}).
 @item
 @cindex string token
 @cindex literal string token
 @item
 @cindex string token
 @cindex literal string token

-@cindex multi-character literal
+@cindex multicharacter literal

 A @dfn{literal string token} is written like a C string constant; for
 example, @code{"<="} is a literal string token.  A literal string token
 doesn't need to be declared unless you need to specify its semantic
 A @dfn{literal string token} is written like a C string constant; for
 example, @code{"<="} is a literal string token.  A literal string token
 doesn't need to be declared unless you need to specify its semantic


@@ -2264,7 +2284,7 @@ retrieve the token number for the literal string token from the
 By convention, a literal string token is used only to represent a token
 that consists of that particular string.  Thus, you should use the token
 type @code{"<="} to represent the string @samp{<=} as a token.  Bison
 By convention, a literal string token is used only to represent a token
 that consists of that particular string.  Thus, you should use the token
 type @code{"<="} to represent the string @samp{<=} as a token.  Bison

-does not enforces this convention, but if you depart from it, people who
+does not enforce this convention, but if you depart from it, people who

 read your program will be confused.
 
 All the escape sequences used in string literals in C can be used in
 read your program will be confused.
 
 All the escape sequences used in string literals in C can be used in


@@ -2284,7 +2304,7 @@ The numeric code for a character token type is simply the ASCII code for
 the character, so @code{yylex} can use the identical character constant to
 generate the requisite code.  Each named token type becomes a C macro in
 the parser file, so @code{yylex} can use the name to stand for the code.
 the character, so @code{yylex} can use the identical character constant to
 generate the requisite code.  Each named token type becomes a C macro in
 the parser file, so @code{yylex} can use the name to stand for the code.

-(This is why periods don't make sense in terminal symbols.)  
+(This is why periods don't make sense in terminal symbols.)

 @xref{Calling Convention, ,Calling Convention for @code{yylex}}.
 
 If @code{yylex} is defined in a separate file, you need to arrange for the
 @xref{Calling Convention, ,Calling Convention for @code{yylex}}.
 
 If @code{yylex} is defined in a separate file, you need to arrange for the


@@ -2313,9 +2333,9 @@ A Bison grammar rule has the following general form:
 @end example
 
 @noindent
 @end example
 
 @noindent

-where @var{result} is the nonterminal symbol that this rule describes
+where @var{result} is the nonterminal symbol that this rule describes,

 and @var{components} are various terminal and nonterminal symbols that
 and @var{components} are various terminal and nonterminal symbols that

-are put together by this rule (@pxref{Symbols}).  
+are put together by this rule (@pxref{Symbols}).

 
 For example,
 
 
 For example,
 


@@ -2399,8 +2419,8 @@ with no components.
 A rule is called @dfn{recursive} when its @var{result} nonterminal appears
 also on its right hand side.  Nearly all Bison grammars need to use
 recursion, because that is the only way to define a sequence of any number
 A rule is called @dfn{recursive} when its @var{result} nonterminal appears
 also on its right hand side.  Nearly all Bison grammars need to use
 recursion, because that is the only way to define a sequence of any number

-of somethings.  Consider this recursive definition of a comma-separated
-sequence of one or more expressions:
+of a particular thing.  Consider this recursive definition of a
+comma-separated sequence of one or more expressions:

 
 @example
 @group
 
 @example
 @group


@@ -2439,7 +2459,7 @@ further explanation of this.
 @dfn{Indirect} or @dfn{mutual} recursion occurs when the result of the
 rule does not appear directly on its right hand side, but does appear
 in rules for other nonterminals which do appear on its right hand
 @dfn{Indirect} or @dfn{mutual} recursion occurs when the result of the
 rule does not appear directly on its right hand side, but does appear
 in rules for other nonterminals which do appear on its right hand

-side.  
+side.

 
 For example:
 
 
 For example:
 


@@ -2464,7 +2484,7 @@ other.
 @node Semantics, Declarations, Recursion, Grammar File
 @section Defining Language Semantics
 @cindex defining language semantics
 @node Semantics, Declarations, Recursion, Grammar File
 @section Defining Language Semantics
 @cindex defining language semantics

-@cindex language semantics, defining 
+@cindex language semantics, defining

 
 The grammar rules for a language determine only the syntax.  The semantics
 are determined by the semantic values associated with various tokens and
 
 The grammar rules for a language determine only the syntax.  The semantics
 are determined by the semantic values associated with various tokens and


@@ -2860,7 +2880,7 @@ the parser, so that the function @code{yylex} (if it is in this file)
 can use the name @var{name} to stand for this token type's code.
 
 Alternatively, you can use @code{%left}, @code{%right}, or @code{%nonassoc}
 can use the name @var{name} to stand for this token type's code.
 
 Alternatively, you can use @code{%left}, @code{%right}, or @code{%nonassoc}

-instead of @code{%token}, if you wish to specify precedence.
+instead of @code{%token}, if you wish to specify associativity and precedence.

 @xref{Precedence Decl, ,Operator Precedence}.
 
 You can explicitly specify the numeric code for a token type by appending
 @xref{Precedence Decl, ,Operator Precedence}.
 
 You can explicitly specify the numeric code for a token type by appending


@@ -2877,7 +2897,7 @@ with each other or with ASCII characters.
 
 In the event that the stack type is a union, you must augment the
 @code{%token} or other token declaration to include the data type
 
 In the event that the stack type is a union, you must augment the
 @code{%token} or other token declaration to include the data type

-alternative delimited by angle-brackets (@pxref{Multiple Types, ,More Than One Value Type}).  
+alternative delimited by angle-brackets (@pxref{Multiple Types, ,More Than One Value Type}).

 
 For example:
 
 
 For example:
 


@@ -2973,7 +2993,7 @@ the one declared later has the higher precedence and is grouped first.
 The @code{%union} declaration specifies the entire collection of possible
 data types for semantic values.  The keyword @code{%union} is followed by a
 pair of braces containing the same thing that goes inside a @code{union} in
 The @code{%union} declaration specifies the entire collection of possible
 data types for semantic values.  The keyword @code{%union} is followed by a
 pair of braces containing the same thing that goes inside a @code{union} in

-C.  
+C.

 
 For example:
 
 
 For example:
 


@@ -3098,24 +3118,32 @@ for example, a nonreentrant program may not be safe to call from a signal
 handler.  In systems with multiple threads of control, a nonreentrant
 program must be called only within interlocks.
 
 handler.  In systems with multiple threads of control, a nonreentrant
 program must be called only within interlocks.
 

-The Bison parser is not normally a reentrant program, because it uses
-statically allocated variables for communication with @code{yylex}.  These
-variables include @code{yylval} and @code{yylloc}.
+Normally, Bison generates a parser which is not reentrant.  This is
+suitable for most uses, and it permits compatibility with YACC.  (The
+standard YACC interfaces are inherently nonreentrant, because they use
+statically allocated variables for communication with @code{yylex},
+including @code{yylval} and @code{yylloc}.)

 
 

-The Bison declaration @code{%pure_parser} says that you want the parser
-to be reentrant.  It looks like this:
+Alternatively, you can generate a pure, reentrant parser.  The Bison
+declaration @code{%pure_parser} says that you want the parser to be
+reentrant.  It looks like this:

 
 @example
 %pure_parser
 @end example
 
 
 @example
 %pure_parser
 @end example
 

-The effect is that the two communication variables 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 Reporting Function @code{yyerror}}).
-The convention for calling @code{yyparse} itself is unchanged.
+The result is that the communication variables @code{yylval} and
+@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
+Reporting Function @code{yyerror}}).  The convention for calling
+@code{yyparse} itself is unchanged.
+
+Whether the parser is pure has nothing to do with the grammar rules.
+You can generate either a pure parser or a nonreentrant parser from any
+valid grammar.

 
 @node Decl Summary,  , Pure Decl, Declarations
 @subsection Bison Declaration Summary
 
 @node Decl Summary,  , Pure Decl, Declarations
 @subsection Bison Declaration Summary


@@ -3152,14 +3180,23 @@ Declare the type of semantic values for a nonterminal symbol
 (@pxref{Type Decl, ,Nonterminal Symbols}).
 
 @item %start
 (@pxref{Type Decl, ,Nonterminal Symbols}).
 
 @item %start

-Specify the grammar's start symbol (@pxref{Start Decl, ,The Start-Symbol}).
+Specify the grammar's start symbol (@pxref{Start Decl, ,The
+Start-Symbol}).

 
 @item %expect
 Declare the expected number of shift-reduce conflicts
 (@pxref{Expect Decl, ,Suppressing Conflict Warnings}).
 
 
 @item %expect
 Declare the expected number of shift-reduce conflicts
 (@pxref{Expect Decl, ,Suppressing Conflict Warnings}).
 

+@item %locations
+Generate the code processing the locations (@pxref{Action Features,
+,Special Features for Use in Actions}).  This mode is enabled as soon as
+the grammar uses the special @samp{@@@var{n}} tokens, but if your
+grammar does not use it, using @samp{%locations} allows for more
+accurate parse error messages.
+

 @item %pure_parser
 @item %pure_parser

-Request a pure (reentrant) parser program (@pxref{Pure Decl, ,A Pure (Reentrant) Parser}).
+Request a pure (reentrant) parser program (@pxref{Pure Decl, ,A Pure
+(Reentrant) Parser}).

 
 @item %no_lines
 Don't generate any @code{#line} preprocessor commands in the parser
 
 @item %no_lines
 Don't generate any @code{#line} preprocessor commands in the parser


@@ -3173,7 +3210,7 @@ file in its own right.
 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
 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
+at 257 except for single-character tokens; Bison assigns token numbers

 sequentially for all tokens starting at 3.)
 
 @item %token_table
 sequentially for all tokens starting at 3.)
 
 @item %token_table


@@ -3202,7 +3239,7 @@ definitions for macros @code{YYNTOKENS}, @code{YYNNTS}, and
 @item YYNTOKENS
 The highest token number, plus one.
 @item YYNNTS
 @item YYNTOKENS
 The highest token number, plus one.
 @item YYNNTS

-The number of non-terminal symbols.
+The number of nonterminal symbols.

 @item YYNRULES
 The number of grammar rules,
 @item YYNSTATES
 @item YYNRULES
 The number of grammar rules,
 @item YYNSTATES


@@ -3256,7 +3293,7 @@ C code in the grammar file, you are likely to run into trouble.
 
 @menu
 * Parser Function::   How to call @code{yyparse} and what it returns.
 
 @menu
 * Parser Function::   How to call @code{yyparse} and what it returns.

-* Lexical::           You must supply a function @code{yylex} 
+* Lexical::           You must supply a function @code{yylex}

                         which reads tokens.
 * Error Reporting::   You must supply a function @code{yyerror}.
 * Action Features::   Special features for use in actions.
                         which reads tokens.
 * Error Reporting::   You must supply a function @code{yyerror}.
 * Action Features::   Special features for use in actions.


@@ -3339,7 +3376,8 @@ signifies end-of-input.
 Here is an example showing these things:
 
 @example
 Here is an example showing these things:
 
 @example

-yylex ()
+int
+yylex (void)

 @{
   @dots{}
   if (c == EOF)     /* Detect end of file. */
 @{
   @dots{}
   if (c == EOF)     /* Detect end of file. */


@@ -3368,9 +3406,9 @@ all others.  In this case, the use of the literal string tokens in
 the grammar file has no effect on @code{yylex}.
 
 @item
 the grammar file has no effect on @code{yylex}.
 
 @item

-@code{yylex} can find the multi-character token in the @code{yytname}
+@code{yylex} can find the multicharacter token in the @code{yytname}

 table.  The index of the token in the table is the token type's code.
 table.  The index of the token in the table is the token type's code.

-The name of a multi-character token is recorded in @code{yytname} with a
+The name of a multicharacter token is recorded in @code{yytname} with a

 double-quote, the token's characters, and another double-quote.  The
 token's characters are not escaped in any way; they appear verbatim in
 the contents of the string in the table.
 double-quote, the token's characters, and another double-quote.  The
 token's characters are not escaped in any way; they appear verbatim in
 the contents of the string in the table.


@@ -3383,7 +3421,8 @@ for (i = 0; i < YYNTOKENS; i++)
   @{
     if (yytname[i] != 0
         && yytname[i][0] == '"'
   @{
     if (yytname[i] != 0
         && yytname[i][0] == '"'

-        && strncmp (yytname[i] + 1, token_buffer, strlen (token_buffer))
+        && strncmp (yytname[i] + 1, token_buffer,
+                    strlen (token_buffer))

         && yytname[i][strlen (token_buffer) + 1] == '"'
         && yytname[i][strlen (token_buffer) + 2] == 0)
       break;
         && yytname[i][strlen (token_buffer) + 1] == '"'
         && yytname[i][strlen (token_buffer) + 2] == 0)
       break;


@@ -3444,16 +3483,17 @@ then the code in @code{yylex} might look like this:
 @subsection Textual Positions of Tokens
 
 @vindex yylloc
 @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 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 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 feature makes the parser noticeably slower.
+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
+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
+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
+feature makes the parser noticeably slower.

 
 @tindex YYLTYPE
 The data type of @code{yylloc} has the name @code{YYLTYPE}.
 
 @tindex YYLTYPE
 The data type of @code{yylloc} has the name @code{YYLTYPE}.


@@ -3470,9 +3510,8 @@ shown here, and pass the information back by storing it through those
 pointers.
 
 @example
 pointers.
 
 @example

-yylex (lvalp, llocp)
-     YYSTYPE *lvalp;
-     YYLTYPE *llocp;
+int
+yylex (YYSTYPE *lvalp, YYLTYPE *llocp)

 @{
   @dots{}
   *lvalp = value;  /* Put value onto Bison stack.  */
 @{
   @dots{}
   *lvalp = value;  /* Put value onto Bison stack.  */


@@ -3574,9 +3613,10 @@ with no arguments, as usual.
 @cindex syntax error
 
 The Bison parser detects a @dfn{parse error} or @dfn{syntax error}
 @cindex syntax error
 
 The Bison parser detects a @dfn{parse error} or @dfn{syntax error}

-whenever it reads a token which cannot satisfy any syntax rule.  A
+whenever it reads a token which cannot satisfy any syntax rule.  An

 action in the grammar can also explicitly proclaim an error, using the
 action in the grammar can also explicitly proclaim an error, using the

-macro @code{YYERROR} (@pxref{Action Features, ,Special Features for Use in Actions}).
+macro @code{YYERROR} (@pxref{Action Features, ,Special Features for Use
+in Actions}).

 
 The Bison parser expects to report the error by calling an error
 reporting function named @code{yyerror}, which you must supply.  It is
 
 The Bison parser expects to report the error by calling an error
 reporting function named @code{yyerror}, which you must supply.  It is


@@ -3586,10 +3626,11 @@ receives one argument.  For a parse error, the string is normally
 
 @findex YYERROR_VERBOSE
 If you define the macro @code{YYERROR_VERBOSE} in the Bison declarations
 
 @findex YYERROR_VERBOSE
 If you define the macro @code{YYERROR_VERBOSE} in the Bison declarations

-section (@pxref{Bison Declarations, ,The Bison Declarations Section}), then Bison provides a more verbose
-and specific error message string instead of just plain @w{@code{"parse
-error"}}.  It doesn't matter what definition you use for
-@code{YYERROR_VERBOSE}, just whether you define it.
+section (@pxref{Bison Declarations, ,The Bison Declarations Section}),
+then Bison provides a more verbose and specific error message string
+instead of just plain @w{@code{"parse error"}}.  It doesn't matter what
+definition you use for @code{YYERROR_VERBOSE}, just whether you define
+it.

 
 The parser can detect one other kind of error: stack overflow.  This
 happens when the input contains constructions that are very deeply
 
 The parser can detect one other kind of error: stack overflow.  This
 happens when the input contains constructions that are very deeply


@@ -3603,8 +3644,8 @@ The following definition suffices in simple programs:
 
 @example
 @group
 
 @example
 @group

-yyerror (s)
-     char *s;
+void
+yyerror (char *s)

 @{
 @end group
 @group
 @{
 @end group
 @group


@@ -3647,7 +3688,7 @@ specified by the @code{%union} declaration.  @xref{Action Types, ,Data Types of
 
 @item $<@var{typealt}>@var{n}
 Like @code{$@var{n}} but specifies alternative @var{typealt} in the
 
 @item $<@var{typealt}>@var{n}
 Like @code{$@var{n}} but specifies alternative @var{typealt} in the

-union specified by the @code{%union} declaration.  
+union specified by the @code{%union} declaration.

 @xref{Action Types, ,Data Types of Values in Actions}.@refill
 
 @item YYABORT;
 @xref{Action Types, ,Data Types of Values in Actions}.@refill
 
 @item YYABORT;


@@ -3702,7 +3743,7 @@ error rules.  @xref{Error Recovery}.
 
 @item yyerrok;
 Resume generating error messages immediately for subsequent syntax
 
 @item yyerrok;
 Resume generating error messages immediately for subsequent syntax

-errors.  This is useful primarily in error rules.  
+errors.  This is useful primarily in error rules.

 @xref{Error Recovery}.
 
 @item @@@var{n}
 @xref{Error Recovery}.
 
 @item @@@var{n}


@@ -3718,8 +3759,8 @@ struct @{
 @};
 @end example
 
 @};
 @end example
 

-Thus, to get the starting line number of the third component, use
-@samp{@@3.first_line}.
+Thus, to get the starting line number of the third component, you would
+use @samp{@@3.first_line}.

 
 In order for the members of this structure to contain valid information,
 you must make @code{yylex} supply this information about each token.
 
 In order for the members of this structure to contain valid information,
 you must make @code{yylex} supply this information about each token.


@@ -3730,8 +3771,8 @@ The use of this feature makes the parser noticeably slower.
 @end table
 
 @node Algorithm, Error Recovery, Interface, Top
 @end table
 
 @node Algorithm, Error Recovery, Interface, Top

-@chapter The Bison Parser Algorithm 
-@cindex Bison parser algorithm 
+@chapter The Bison Parser Algorithm
+@cindex Bison parser algorithm

 @cindex algorithm of parser
 @cindex shifting
 @cindex reduction
 @cindex algorithm of parser
 @cindex shifting
 @cindex reduction


@@ -3983,7 +4024,7 @@ expr:     expr '-' expr
 
 @noindent
 Suppose the parser has seen the tokens @samp{1}, @samp{-} and @samp{2};
 
 @noindent
 Suppose the parser has seen the tokens @samp{1}, @samp{-} and @samp{2};

-should it reduce them via the rule for the addition operator?  It depends
+should it reduce them via the rule for the subtraction operator?  It depends

 on the next token.  Of course, if the next token is @samp{)}, we must
 reduce; shifting is invalid because no single rule can reduce the token
 sequence @w{@samp{- 2 )}} or anything starting with that.  But if the next
 on the next token.  Of course, if the next token is @samp{)}, we must
 reduce; shifting is invalid because no single rule can reduce the token
 sequence @w{@samp{- 2 )}} or anything starting with that.  But if the next


@@ -3994,7 +4035,7 @@ results.
 To decide which one Bison should do, we must consider the
 results.  If the next operator token @var{op} is shifted, then it
 must be reduced first in order to permit another opportunity to
 To decide which one Bison should do, we must consider the
 results.  If the next operator token @var{op} is shifted, then it
 must be reduced first in order to permit another opportunity to

-reduce the sum.  The result is (in effect) @w{@samp{1 - (2
+reduce the difference.  The result is (in effect) @w{@samp{1 - (2

 @var{op} 3)}}.  On the other hand, if the subtraction is reduced
 before shifting @var{op}, the result is @w{@samp{(1 - 2) @var{op}
 3}}.  Clearly, then, the choice of shift or reduce should depend
 @var{op} 3)}}.  On the other hand, if the subtraction is reduced
 before shifting @var{op}, the result is @w{@samp{(1 - 2) @var{op}
 3}}.  Clearly, then, the choice of shift or reduce should depend


@@ -4317,7 +4358,7 @@ name_list:
 @end example
 
 It would seem that this grammar can be parsed with only a single token
 @end example
 
 It would seem that this grammar can be parsed with only a single token

-of look-ahead: when a @code{param_spec} is being read, an @code{ID} is 
+of look-ahead: when a @code{param_spec} is being read, an @code{ID} is

 a @code{name} if a comma or colon follows, or a @code{type} if another
 @code{ID} follows.  In other words, this grammar is LR(1).
 
 a @code{name} if a comma or colon follows, or a @code{type} if another
 @code{ID} follows.  In other words, this grammar is LR(1).
 


@@ -4444,7 +4485,7 @@ recognize the special token @code{error}.  This is a terminal symbol that
 is always defined (you need not declare it) and reserved for error
 handling.  The Bison parser generates an @code{error} token whenever a
 syntax error happens; if you have provided a rule to recognize this token
 is always defined (you need not declare it) and reserved for error
 handling.  The Bison parser generates an @code{error} token whenever a
 syntax error happens; if you have provided a rule to recognize this token

-in the current context, the parse can continue.  
+in the current context, the parse can continue.

 
 For example:
 
 
 For example:
 


@@ -4600,7 +4641,7 @@ static int foo (lose);   /* @r{redeclare @code{foo} as function} */
 Unfortunately, the name being declared is separated from the declaration
 construct itself by a complicated syntactic structure---the ``declarator''.
 
 Unfortunately, the name being declared is separated from the declaration
 construct itself by a complicated syntactic structure---the ``declarator''.
 

-As a result, the part of Bison parser for C needs to be duplicated, with
+As a result, part of the Bison parser for C needs to be duplicated, with

 all the nonterminal names changed: once for parsing a declaration in which
 a typedef name can be redefined, and once for parsing a declaration in
 which that can't be done.  Here is a part of the duplication, with actions
 all the nonterminal names changed: once for parsing a declaration in which
 a typedef name can be redefined, and once for parsing a declaration in
 which that can't be done.  Here is a part of the duplication, with actions


@@ -4682,7 +4723,7 @@ 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
 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 
+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.
 
 (@pxref{C Declarations, ,The C Declarations Section}).  You must also write the code in @code{yylex}
 to obey the flag.
 


@@ -4754,7 +4795,7 @@ 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
 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 
+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.
 (@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.


@@ -4814,10 +4855,7 @@ calculator (@pxref{Mfcalc Decl, ,Declarations for @code{mfcalc}}):
 #define YYPRINT(file, type, value)   yyprint (file, type, value)
 
 static void
 #define YYPRINT(file, type, value)   yyprint (file, type, value)
 
 static void

-yyprint (file, type, value)
-     FILE *file;
-     int type;
-     YYSTYPE value;
+yyprint (FILE *file, int type, YYSTYPE value)

 @{
   if (type == VAR)
     fprintf (file, " %s", value.tptr->name);
 @{
   if (type == VAR)
     fprintf (file, " %s", value.tptr->name);


@@ -4845,13 +4883,14 @@ with @samp{.tab.c}.  Thus, the @samp{bison foo.y} filename yields
 @file{hack/foo.tab.c}.@refill
 
 @menu
 @file{hack/foo.tab.c}.@refill
 
 @menu

-* Bison Options::     All the options described in detail, 
+* Bison Options::     All the options described in detail,

                        in alphabetical order by short options.
                        in alphabetical order by short options.

+* Environment Variables::  Variables which affect Bison execution.

 * Option Cross Key::  Alphabetical list of long options.
 * VMS Invocation::    Bison command syntax on VMS.
 @end menu
 
 * Option Cross Key::  Alphabetical list of long options.
 * VMS Invocation::    Bison command syntax on VMS.
 @end menu
 

-@node Bison Options, Option Cross Key,  , Invocation
+@node Bison Options, Environment Variables,  , Invocation

 @section Bison Options
 
 Bison supports both traditional single-letter options and mnemonic long
 @section Bison Options
 
 Bison supports both traditional single-letter options and mnemonic long


@@ -4865,25 +4904,56 @@ Here is a list of options that can be used with Bison, alphabetized by
 short option.  It is followed by a cross key alphabetized by long
 option.
 
 short option.  It is followed by a cross key alphabetized by long
 option.
 

-@table @samp
-@item -b @var{file-prefix}
-@itemx --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}.c}.
+@c Please, keep this ordered as in `bison --help'.
+@noindent
+Operations modes:
+@table @option
+@item -h
+@itemx --help
+Print a summary of the command-line options to Bison and exit.

 
 

-@item -d
-@itemx --defines
-Write an extra output file containing macro definitions for the token
-type names defined in the grammar and the semantic value type
-@code{YYSTYPE}, as well as a few @code{extern} variable declarations.
+@item -V
+@itemx --version
+Print the version number of Bison and exit.

 
 

-If the parser output file is named @file{@var{name}.c} then this file
-is named @file{@var{name}.h}.@refill
+@need 1750
+@item -y
+@itemx --yacc
+@itemx --fixed-output-files
+Equivalent to @samp{-o y.tab.c}; the parser output file is called
+@file{y.tab.c}, and the other outputs are called @file{y.output} and
+@file{y.tab.h}.  The purpose of this option is to imitate Yacc's output
+file name conventions.  Thus, the following shell script can substitute
+for Yacc:@refill

 
 

-This output file is essential if you wish to put the definition of
-@code{yylex} in a separate source file, because @code{yylex} needs to
-be able to refer to token type codes and the variable
-@code{yylval}.  @xref{Token Values, ,Semantic Values of Tokens}.@refill
+@example
+bison -y $*
+@end example
+@end table
+
+@noindent
+Tuning the parser:
+
+@table @option
+@item -t
+@itemx --debug
+Output a definition of the macro @code{YYDEBUG} into the parser file,
+so that the debugging facilities are compiled.  @xref{Debugging, ,Debugging Your Parser}.
+
+@item --locations
+Pretend that @code{%locactions} was specified.  @xref{Decl Summary}.
+
+@item -p @var{prefix}
+@itemx --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
+is @code{yyparse}, @code{yylex}, @code{yyerror}, @code{yynerrs},
+@code{yylval}, @code{yychar} and @code{yydebug}.
+
+For example, if you use @samp{-p c}, the names become @code{cparse},
+@code{clex}, and so on.
+
+@xref{Multiple Parsers, ,Multiple Parsers in the Same Program}.

 
 @item -l
 @itemx --no-lines
 
 @item -l
 @itemx --no-lines


@@ -4903,33 +4973,37 @@ This option also tells Bison to write the C code for the grammar actions
 into a file named @file{@var{filename}.act}, in the form of a
 brace-surrounded body fit for a @code{switch} statement.
 
 into a file named @file{@var{filename}.act}, in the form of a
 brace-surrounded body fit for a @code{switch} statement.
 

-@item -o @var{outfile}
-@itemx --output-file=@var{outfile}
-Specify the name @var{outfile} for the parser file.
+@item -r
+@itemx --raw
+Pretend that @code{%raw} was specified.  @xref{Decl Summary}.

 
 

-The other output files' names are constructed from @var{outfile}
-as described under the @samp{-v} and @samp{-d} options.
+@item -k
+@itemx --token-table
+Pretend that @code{%token_table} was specified.  @xref{Decl Summary}.
+@end table

 
 

-@item -p @var{prefix}
-@itemx --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
-is @code{yyparse}, @code{yylex}, @code{yyerror}, @code{yynerrs},
-@code{yylval}, @code{yychar} and @code{yydebug}.
+@noindent
+Adjust the output:

 
 

-For example, if you use @samp{-p c}, the names become @code{cparse},
-@code{clex}, and so on.
+@table @option
+@item -d
+@itemx --defines
+Write an extra output file containing macro definitions for the token
+type names defined in the grammar and the semantic value type
+@code{YYSTYPE}, as well as a few @code{extern} variable declarations.

 
 

-@xref{Multiple Parsers, ,Multiple Parsers in the Same Program}.
+If the parser output file is named @file{@var{name}.c} then this file
+is named @file{@var{name}.h}.@refill

 
 

-@item -r
-@itemx --raw
-Pretend that @code{%raw} was specified.  @xref{Decl Summary}.
+This output file is essential if you wish to put the definition of
+@code{yylex} in a separate source file, because @code{yylex} needs to
+be able to refer to token type codes and the variable
+@code{yylval}.  @xref{Token Values, ,Semantic Values of Tokens}.@refill

 
 

-@item -t
-@itemx --debug
-Output a definition of the macro @code{YYDEBUG} into the parser file,
-so that the debugging facilities are compiled.  @xref{Debugging, ,Debugging Your Parser}.
+@item -b @var{file-prefix}
+@itemx --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}.c}.

 
 @item -v
 @itemx --verbose
 
 @item -v
 @itemx --verbose


@@ -4947,30 +5021,40 @@ Therefore, if the input file is @file{foo.y}, then the parser file is
 called @file{foo.tab.c} by default.  As a consequence, the verbose
 output file is called @file{foo.output}.@refill
 
 called @file{foo.tab.c} by default.  As a consequence, the verbose
 output file is called @file{foo.output}.@refill
 

-@item -V
-@itemx --version
-Print the version number of Bison and exit.
+@item -o @var{outfile}
+@itemx --output-file=@var{outfile}
+Specify the name @var{outfile} for the parser file.

 
 

-@item -h
-@itemx --help
-Print a summary of the command-line options to Bison and exit.
+The other output files' names are constructed from @var{outfile}
+as described under the @samp{-v} and @samp{-d} options.
+@end table

 
 

-@need 1750
-@item -y
-@itemx --yacc
-@itemx --fixed-output-files
-Equivalent to @samp{-o y.tab.c}; the parser output file is called
-@file{y.tab.c}, and the other outputs are called @file{y.output} and
-@file{y.tab.h}.  The purpose of this option is to imitate Yacc's output
-file name conventions.  Thus, the following shell script can substitute
-for Yacc:@refill
+@node Environment Variables, Option Cross Key, Bison Options, Invocation
+@section Environment Variables
+@cindex environment variables
+@cindex BISON_HAIRY
+@cindex BISON_SIMPLE
+
+Here is a list of environment variables which affect the way Bison
+runs.
+
+@table @samp
+@item BISON_SIMPLE
+@itemx BISON_HAIRY
+Much of the parser generated by Bison is copied verbatim from a file
+called @file{bison.simple}.  If Bison cannot find that file, or if you
+would like to direct Bison to use a different copy, setting the
+environment variable @code{BISON_SIMPLE} to the path of the file will
+cause Bison to use that copy instead.
+
+When the @samp{%semantic_parser} declaration is used, Bison copies from
+a file called @file{bison.hairy} instead.  The location of this file can
+also be specified or overridden in a similar fashion, with the
+@code{BISON_HAIRY} environment variable.

 
 

-@example
-bison -y $*
-@end example

 @end table
 
 @end table
 

-@node Option Cross Key, VMS Invocation, Bison Options, Invocation
+@node Option Cross Key, VMS Invocation, Environment Variables, Invocation

 @section Option Cross Key
 
 Here is a list of options, alphabetized by long option, to help you find
 @section Option Cross Key
 
 Here is a list of options, alphabetized by long option, to help you find


@@ -5008,7 +5092,7 @@ the corresponding short option.
 --no-lines                            -l
 --no-parser                           -n
 --output-file=@var{outfile}                 -o @var{outfile}
 --no-lines                            -l
 --no-parser                           -n
 --output-file=@var{outfile}                 -o @var{outfile}

---raw                                 -r                       
+--raw                                 -r

 --token-table                         -k
 --verbose                             -v
 --version                             -V
 --token-table                         -k
 --verbose                             -v
 --version                             -V


@@ -5062,11 +5146,12 @@ token is reset to the token that originally caused the violation.
 @item YYABORT
 Macro to pretend that an unrecoverable syntax error has occurred, by
 making @code{yyparse} return 1 immediately.  The error reporting
 @item YYABORT
 Macro to pretend that an unrecoverable syntax error has occurred, by
 making @code{yyparse} return 1 immediately.  The error reporting

-function @code{yyerror} is not called.  @xref{Parser Function, ,The Parser Function @code{yyparse}}.
+function @code{yyerror} is not called.  @xref{Parser Function, ,The
+Parser Function @code{yyparse}}.

 
 @item YYACCEPT
 Macro to pretend that a complete utterance of the language has been
 
 @item YYACCEPT
 Macro to pretend that a complete utterance of the language has been

-read, by making @code{yyparse} return 0 immediately.  
+read, by making @code{yyparse} return 0 immediately.

 @xref{Parser Function, ,The Parser Function @code{yyparse}}.
 
 @item YYBACKUP
 @xref{Parser Function, ,The Parser Function @code{yyparse}}.
 
 @item YYBACKUP


@@ -5117,10 +5202,10 @@ Macro for the data type of semantic values; @code{int} by default.
 @xref{Value Type, ,Data Types of Semantic Values}.
 
 @item yychar
 @xref{Value Type, ,Data Types of Semantic Values}.
 
 @item yychar

-External integer variable that contains the integer value of the
-current look-ahead token.  (In a pure parser, it is a local variable
-within @code{yyparse}.)  Error-recovery rule actions may examine this
-variable.  @xref{Action Features, ,Special Features for Use in Actions}.
+External integer variable that contains the integer value of the current
+look-ahead token.  (In a pure parser, it is a local variable within
+@code{yyparse}.)  Error-recovery rule actions may examine this variable.
+@xref{Action Features, ,Special Features for Use in Actions}.

 
 @item yyclearin
 Macro used in error-recovery rule actions.  It clears the previous
 
 @item yyclearin
 Macro used in error-recovery rule actions.  It clears the previous


@@ -5138,7 +5223,8 @@ after a parse error.  @xref{Error Recovery}.
 @item yyerror
 User-supplied function to be called by @code{yyparse} on error.  The
 function receives one argument, a pointer to a character string
 @item yyerror
 User-supplied function to be called by @code{yyparse} on error.  The
 function receives one argument, a pointer to a character string

-containing an error message.  @xref{Error Reporting, ,The Error Reporting Function @code{yyerror}}.
+containing an error message.  @xref{Error Reporting, ,The Error
+Reporting Function @code{yyerror}}.

 
 @item yylex
 User-supplied lexical analyzer function, called with no arguments
 
 @item yylex
 User-supplied lexical analyzer function, called with no arguments


@@ -5151,16 +5237,17 @@ variable within @code{yyparse}, and its address is passed to
 @code{yylex}.)  @xref{Token Values, ,Semantic Values of Tokens}.
 
 @item yylloc
 @code{yylex}.)  @xref{Token Values, ,Semantic Values of Tokens}.
 
 @item yylloc

-External variable in which @code{yylex} should place the line and
-column numbers associated with a token.  (In a pure parser, it is a
-local variable within @code{yyparse}, and its address is passed to
+External variable in which @code{yylex} should place the line and column
+numbers associated with a token.  (In a pure parser, it is a local
+variable within @code{yyparse}, and its address is passed to

 @code{yylex}.)  You can ignore this variable if you don't use the
 @code{yylex}.)  You can ignore this variable if you don't use the

-@samp{@@} feature in the grammar actions.  @xref{Token Positions, ,Textual Positions of Tokens}.
+@samp{@@} feature in the grammar actions.  @xref{Token Positions,
+,Textual Positions of Tokens}.

 
 @item yynerrs
 
 @item yynerrs

-Global variable which Bison increments each time there is a parse
-error.  (In a pure parser, it is a local variable within
-@code{yyparse}.)  @xref{Error Reporting, ,The Error Reporting Function @code{yyerror}}.
+Global variable which Bison increments each time there is a parse error.
+(In a pure parser, it is a local variable within @code{yyparse}.)
+@xref{Error Reporting, ,The Error Reporting Function @code{yyerror}}.

 
 @item yyparse
 The parser function produced by Bison; call this function to start
 
 @item yyparse
 The parser function produced by Bison; call this function to start


@@ -5223,15 +5310,17 @@ Bison declarations section or the additional C code section.
 @xref{Grammar Layout, ,The Overall Layout of a Bison Grammar}.
 
 @item %@{ %@}
 @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 Grammar}.
+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
+Grammar}.

 
 @item /*@dots{}*/
 Comment delimiters, as in C.
 
 @item :
 
 @item /*@dots{}*/
 Comment delimiters, as in C.
 
 @item :

-Separates a rule's result from its components.  @xref{Rules, ,Syntax of Grammar Rules}.
+Separates a rule's result from its components.  @xref{Rules, ,Syntax of
+Grammar Rules}.

 
 @item ;
 Terminates a rule.  @xref{Rules, ,Syntax of Grammar Rules}.
 
 @item ;
 Terminates a rule.  @xref{Rules, ,Syntax of Grammar Rules}.


@@ -5248,13 +5337,15 @@ Separates alternate rules for the same result nonterminal.
 @table @asis
 @item Backus-Naur Form (BNF)
 Formal method of specifying context-free grammars.  BNF was first used
 @table @asis
 @item Backus-Naur Form (BNF)
 Formal method of specifying context-free grammars.  BNF was first used

-in the @cite{ALGOL-60} report, 1963.  @xref{Language and Grammar, ,Languages and Context-Free Grammars}.
+in the @cite{ALGOL-60} report, 1963.  @xref{Language and Grammar,
+,Languages and Context-Free Grammars}.

 
 @item Context-free grammars
 Grammars specified as rules that can be applied regardless of context.
 Thus, if there is a rule which says that an integer can be used as an
 expression, integers are allowed @emph{anywhere} an expression is
 
 @item Context-free grammars
 Grammars specified as rules that can be applied regardless of context.
 Thus, if there is a rule which says that an integer can be used as an
 expression, integers are allowed @emph{anywhere} an expression is

-permitted.  @xref{Language and Grammar, ,Languages and Context-Free Grammars}.
+permitted.  @xref{Language and Grammar, ,Languages and Context-Free
+Grammars}.

 
 @item Dynamic allocation
 Allocation of memory that occurs during execution, rather than at
 
 @item Dynamic allocation
 Allocation of memory that occurs during execution, rather than at


@@ -5274,7 +5365,7 @@ rules.  @xref{Algorithm, ,The Bison Parser Algorithm }.
 
 @item Grouping
 A language construct that is (in general) grammatically divisible;
 
 @item Grouping
 A language construct that is (in general) grammatically divisible;

-for example, `expression' or `declaration' in C.  
+for example, `expression' or `declaration' in C.

 @xref{Language and Grammar, ,Languages and Context-Free Grammars}.
 
 @item Infix operator
 @xref{Language and Grammar, ,Languages and Context-Free Grammars}.
 
 @item Infix operator


@@ -5295,8 +5386,9 @@ Operators having left associativity are analyzed from left to right:
 @samp{c}.  @xref{Precedence, ,Operator Precedence}.
 
 @item Left recursion
 @samp{c}.  @xref{Precedence, ,Operator Precedence}.
 
 @item Left recursion

-A rule whose result symbol is also its first component symbol;
-for example, @samp{expseq1 : expseq1 ',' exp;}.  @xref{Recursion, ,Recursive Rules}.
+A rule whose result symbol is also its first component symbol; for
+example, @samp{expseq1 : expseq1 ',' exp;}.  @xref{Recursion, ,Recursive
+Rules}.

 
 @item Left-to-right parsing
 Parsing a sentence of a language by analyzing it token by token from
 
 @item Left-to-right parsing
 Parsing a sentence of a language by analyzing it token by token from


@@ -5311,11 +5403,12 @@ A flag, set by actions in the grammar rules, which alters the way
 tokens are parsed.  @xref{Lexical Tie-ins}.
 
 @item Literal string token
 tokens are parsed.  @xref{Lexical Tie-ins}.
 
 @item Literal string token

-A token which constists of two or more fixed characters.
+A token which consists of two or more fixed characters.

 @xref{Symbols}.
 
 @item Look-ahead token
 @xref{Symbols}.
 
 @item Look-ahead token

-A token already read but not yet shifted.  @xref{Look-Ahead, ,Look-Ahead Tokens}.
+A token already read but not yet shifted.  @xref{Look-Ahead, ,Look-Ahead
+Tokens}.

 
 @item LALR(1)
 The class of context-free grammars that Bison (like most other parser
 
 @item LALR(1)
 The class of context-free grammars that Bison (like most other parser


@@ -5346,7 +5439,8 @@ performs some operation.
 
 @item Reduction
 Replacing a string of nonterminals and/or terminals with a single
 
 @item Reduction
 Replacing a string of nonterminals and/or terminals with a single

-nonterminal, according to a grammar rule.  @xref{Algorithm, ,The Bison Parser Algorithm }.
+nonterminal, according to a grammar rule.  @xref{Algorithm, ,The Bison
+Parser Algorithm }.

 
 @item Reentrant
 A reentrant subprogram is a subprogram which can be in invoked any
 
 @item Reentrant
 A reentrant subprogram is a subprogram which can be in invoked any


@@ -5357,8 +5451,9 @@ invocations.  @xref{Pure Decl, ,A Pure (Reentrant) Parser}.
 A language in which all operators are postfix operators.
 
 @item Right recursion
 A language in which all operators are postfix operators.
 
 @item Right recursion

-A rule whose result symbol is also its last component symbol;
-for example, @samp{expseq1: exp ',' expseq1;}.  @xref{Recursion, ,Recursive Rules}.
+A rule whose result symbol is also its last component symbol; for
+example, @samp{expseq1: exp ',' expseq1;}.  @xref{Recursion, ,Recursive
+Rules}.

 
 @item Semantics
 In computer languages, the semantics are specified by the actions
 
 @item Semantics
 In computer languages, the semantics are specified by the actions


@@ -5377,7 +5472,7 @@ A single character that is recognized and interpreted as is.
 @item Start symbol
 The nonterminal symbol that stands for a complete valid utterance in
 the language being parsed.  The start symbol is usually listed as the
 @item Start symbol
 The nonterminal symbol that stands for a complete valid utterance in
 the language being parsed.  The start symbol is usually listed as the

-first nonterminal symbol in a language specification.  
+first nonterminal symbol in a language specification.

 @xref{Start Decl, ,The Start-Symbol}.
 
 @item Symbol table
 @xref{Start Decl, ,The Start-Symbol}.
 
 @item Symbol table


@@ -5392,9 +5487,9 @@ The input of the Bison parser is a stream of tokens which comes from
 the lexical analyzer.  @xref{Symbols}.
 
 @item Terminal symbol
 the lexical analyzer.  @xref{Symbols}.
 
 @item Terminal symbol

-A grammar symbol that has no rules in the grammar and therefore
-is grammatically indivisible.  The piece of text it represents
-is a token.  @xref{Language and Grammar, ,Languages and Context-Free Grammars}.
+A grammar symbol that has no rules in the grammar and therefore is
+grammatically indivisible.  The piece of text it represents is a token.
+@xref{Language and Grammar, ,Languages and Context-Free Grammars}.

 @end table
 
 @node Index,  , Glossary, Top
 @end table
 
 @node Index,  , Glossary, Top


@@ -5402,34 +5497,4 @@ is a token.  @xref{Language and Grammar, ,Languages and Context-Free Grammars}.
 
 @printindex cp
 
 
 @printindex cp
 

-@contents
-

 @bye
 @bye

-
-
-\f
-
-@c old menu
-
-* Introduction::
-* Conditions::
-* Copying::           The GNU General Public License says
-                        how you can copy and share Bison
-
-Tutorial sections:
-* Concepts::          Basic concepts for understanding Bison.
-* Examples::          Three simple explained examples of using Bison.
-
-Reference sections:
-* Grammar File::      Writing Bison declarations and rules.
-* Interface::         C-language interface to the parser function @code{yyparse}.
-* Algorithm::         How the Bison parser works at run-time.
-* Error Recovery::    Writing rules for error recovery.
-* Context Dependency::What to do if your language syntax is too
-                        messy for Bison to handle straightforwardly.
-* Debugging::         Debugging Bison parsers that parse wrong.
-* 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.
-* Index::             Cross-references to the text.
-