X-Git-Url: https://git.saurik.com/bison.git/blobdiff_plain/7da99edea76d6148c776214a71bc09dacfc0cb7b..1ce5149ac8ffb10e03301661ac3abcc39de31702:/doc/bison.texinfo?ds=inline

diff --git a/doc/bison.texinfo b/doc/bison.texinfo
index 9f769460..0d3ce7d5 100644
--- a/doc/bison.texinfo
+++ b/doc/bison.texinfo
@@ -5,9 +5,7 @@
 @settitle Bison @value{VERSION}
 @setchapternewpage odd
 
-@iftex
 @finalout
-@end iftex
 
 @c SMALL BOOK version
 @c This edition has been formatted so that you can format and print it in
@@ -23,6 +21,7 @@
 @c Check COPYRIGHT dates.  should be updated in the titlepage, ifinfo
 @c titlepage; should NOT be changed in the GPL.  --mew
 
+@c FIXME: I don't understand this `iftex'.  Obsolete? --akim.
 @iftex
 @syncodeindex fn cp
 @syncodeindex vr cp
@@ -47,7 +46,7 @@ END-INFO-DIR-ENTRY
 This file documents the Bison parser generator.
 
 Copyright (C) 1988, 1989, 1990, 1991, 1992, 1993, 1995, 1998, 1999,
-2000, 2001
+2000, 2001, 2002
 Free Software Foundation, Inc.
 
 Permission is granted to make and distribute verbatim copies of
@@ -89,7 +88,7 @@ instead of in the original English.
 @page
 @vskip 0pt plus 1filll
 Copyright @copyright{} 1988, 1989, 1990, 1991, 1992, 1993, 1995, 1998,
-1999, 2000, 2001
+1999, 2000, 2001, 2002
 Free Software Foundation, Inc.
 
 @sp 2
@@ -154,7 +153,7 @@ Reference sections:
 * 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.
+* Debugging::         Understanding or debugging Bison parsers.
 * 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.
@@ -299,6 +298,11 @@ Handling Context Dependencies
 * Tie-in Recovery::   Lexical tie-ins have implications for how
                         error recovery rules must be written.
 
+Understanding or Debugging Your Parser
+
+* Understanding::     Understanding the structure of your parser.
+* Tracing::           Tracing the execution of your parser.
+
 Invoking Bison
 
 * Bison Options::     All the options described in detail,
@@ -433,7 +437,7 @@ smaller constructs according to grammatical rules are called
 @dfn{nonterminal symbols}; those which can't be subdivided are called
 @dfn{terminal symbols} or @dfn{token types}.  We call a piece of input
 corresponding to a single terminal symbol a @dfn{token}, and a piece
-corresponding to a single nonterminal symbol a @dfn{grouping}.@refill
+corresponding to a single nonterminal symbol a @dfn{grouping}.
 
 We can use the C language as an example of what symbols, terminal and
 nonterminal, mean.  The tokens of C are identifiers, constants (numeric and
@@ -447,16 +451,26 @@ lexicography, not grammar.)
 
 Here is a simple C function subdivided into tokens:
 
+@ifinfo
+@example
+int             /* @r{keyword `int'} */
+square (int x)  /* @r{identifier, open-paren, identifier,}
+                   @r{identifier, close-paren} */
+@{               /* @r{open-brace} */
+  return x * x; /* @r{keyword `return', identifier, asterisk,
+                   identifier, semicolon} */
+@}               /* @r{close-brace} */
+@end example
+@end ifinfo
+@ifnotinfo
 @example
 int             /* @r{keyword `int'} */
-square (x)      /* @r{identifier, open-paren,} */
-                /* @r{identifier, close-paren} */
-     int x;     /* @r{keyword `int', identifier, semicolon} */
+square (int x)  /* @r{identifier, open-paren, identifier, identifier, close-paren} */
 @{               /* @r{open-brace} */
-  return x * x; /* @r{keyword `return', identifier,} */
-                /* @r{asterisk, identifier, semicolon} */
+  return x * x; /* @r{keyword `return', identifier, asterisk, identifier, semicolon} */
 @}               /* @r{close-brace} */
 @end example
+@end ifnotinfo
 
 The syntactic groupings of C include the expression, the statement, the
 declaration, and the function definition.  These are represented in the
@@ -555,7 +569,7 @@ if a rule mentions the terminal symbol `integer constant', it means that
 @emph{any} integer constant is grammatically valid in that position.  The
 precise value of the constant is irrelevant to how to parse the input: if
 @samp{x+4} is grammatical then @samp{x+1} or @samp{x+3989} is equally
-grammatical.@refill
+grammatical.
 
 But the precise value is very important for what the input means once it is
 parsed.  A compiler is useless if it fails to distinguish between 4, 1 and
@@ -567,7 +581,7 @@ The token type is a terminal symbol defined in the grammar, such as
 @code{INTEGER}, @code{IDENTIFIER} or @code{','}.  It tells everything
 you need to know to decide where the token may validly appear and how to
 group it with other tokens.  The grammar rules know nothing about tokens
-except their types.@refill
+except their types.
 
 The semantic value has all the rest of the information about the
 meaning of the token, such as the value of an integer, or the name of an
@@ -666,12 +680,13 @@ the grammar rules---for example, to build identifiers and operators into
 expressions.  As it does this, it runs the actions for the grammar rules it
 uses.
 
-The tokens come from a function called the @dfn{lexical analyzer} that you
-must supply in some fashion (such as by writing it in C).  The Bison parser
-calls the lexical analyzer each time it wants a new token.  It doesn't know
-what is ``inside'' the tokens (though their semantic values may reflect
-this).  Typically the lexical analyzer makes the tokens by parsing
-characters of text, but Bison does not depend on this.  @xref{Lexical, ,The Lexical Analyzer Function @code{yylex}}.
+The tokens come from a function called the @dfn{lexical analyzer} that
+you must supply in some fashion (such as by writing it in C).  The Bison
+parser calls the lexical analyzer each time it wants a new token.  It
+doesn't know what is ``inside'' the tokens (though their semantic values
+may reflect this).  Typically the lexical analyzer makes the tokens by
+parsing characters of text, but Bison does not depend on this.
+@xref{Lexical, ,The Lexical Analyzer Function @code{yylex}}.
 
 The Bison parser file is C code which defines a function named
 @code{yyparse} which implements that grammar.  This function does not make
@@ -683,7 +698,7 @@ arrange for it to call @code{yyparse} or the parser will never run.
 @xref{Interface, ,Parser C-Language Interface}.
 
 Aside from the token type names and the symbols in the actions you
-write, all variable and function names used in the Bison parser file
+write, all symbols defined in the Bison parser file itself
 begin with @samp{yy} or @samp{YY}.  This includes interface functions
 such as the lexical analyzer function @code{yylex}, the error reporting
 function @code{yyerror} and the parser function @code{yyparse} itself.
@@ -692,6 +707,14 @@ Therefore, you should avoid using C identifiers starting with @samp{yy}
 or @samp{YY} in the Bison grammar file except for the ones defined in
 this manual.
 
+In some cases the Bison parser file includes system headers, and in
+those cases your code should respect the identifiers reserved by those
+headers.  On some non-@sc{gnu} hosts, @code{<alloca.h>},
+@code{<stddef.h>}, and @code{<stdlib.h>} are included as needed to
+declare memory allocators and related types.  Other system headers may
+be included if you define @code{YYDEBUG} to a nonzero value
+(@pxref{Tracing, ,Tracing Your Parser}).
+
 @node Stages
 @section Stages in Using Bison
 @cindex stages in using Bison
@@ -703,15 +726,16 @@ to a working compiler or interpreter, has these parts:
 @enumerate
 @item
 Formally specify the grammar in a form recognized by Bison
-(@pxref{Grammar File, ,Bison Grammar Files}).  For each grammatical rule in the language,
-describe the action that is to be taken when an instance of that rule
-is recognized.  The action is described by a sequence of C statements.
+(@pxref{Grammar File, ,Bison Grammar Files}).  For each grammatical rule
+in the language, describe the action that is to be taken when an
+instance of that rule is recognized.  The action is described by a
+sequence of C statements.
 
 @item
-Write a lexical analyzer to process input and pass tokens to the
-parser.  The lexical analyzer may be written by hand in C
-(@pxref{Lexical, ,The Lexical Analyzer Function @code{yylex}}).  It could also be produced using Lex, but the use
-of Lex is not discussed in this manual.
+Write a lexical analyzer to process input and pass tokens to the parser.
+The lexical analyzer may be written by hand in C (@pxref{Lexical, ,The
+Lexical Analyzer Function @code{yylex}}).  It could also be produced
+using Lex, but the use of Lex is not discussed in this manual.
 
 @item
 Write a controlling function that calls the Bison-produced parser.
@@ -746,7 +770,7 @@ general form of a Bison grammar file is as follows:
 
 @example
 %@{
-@var{Prologue (declarations)}
+@var{Prologue}
 %@}
 
 @var{Bison declarations}
@@ -754,7 +778,7 @@ general form of a Bison grammar file is as follows:
 %%
 @var{Grammar rules}
 %%
-@var{Epilogue (additional code)}
+@var{Epilogue}
 @end example
 
 @noindent
@@ -865,9 +889,10 @@ which is a floating point number.
 The @code{#include} directive is used to declare the exponentiation
 function @code{pow}.
 
-The second section, Bison declarations, provides information to Bison about
-the token types (@pxref{Bison Declarations, ,The Bison Declarations Section}).  Each terminal symbol that is
-not a single-character literal must be declared here.  (Single-character
+The second section, Bison declarations, provides information to Bison
+about the token types (@pxref{Bison Declarations, ,The Bison
+Declarations Section}).  Each terminal symbol that is not a
+single-character literal must be declared here.  (Single-character
 literals normally don't need to be declared.)  In this example, all the
 arithmetic operators are designated by single-character literals, so the
 only terminal symbol that needs to be declared is @code{NUM}, the token
@@ -1047,9 +1072,10 @@ The latter, however, is much more readable.
 @cindex writing a lexical analyzer
 @cindex lexical analyzer, writing
 
-The lexical analyzer's job is low-level parsing: converting characters or
-sequences of characters into tokens.  The Bison parser gets its tokens by
-calling the lexical analyzer.  @xref{Lexical, ,The Lexical Analyzer Function @code{yylex}}.
+The lexical analyzer's job is low-level parsing: converting characters
+or sequences of characters into tokens.  The Bison parser gets its
+tokens by calling the lexical analyzer.  @xref{Lexical, ,The Lexical
+Analyzer Function @code{yylex}}.
 
 Only a simple lexical analyzer is needed for the RPN calculator.  This
 lexical analyzer skips blanks and tabs, then reads in numbers as
@@ -1061,7 +1087,7 @@ The return value of the lexical analyzer function is a numeric code which
 represents a token type.  The same text used in Bison rules to stand for
 this token type is also a C expression for the numeric code for the type.
 This works in two ways.  If the token type is a character literal, then its
-numeric code is the ASCII code for that character; you can use the same
+numeric code is that of the character; you can use the same
 character literal in the lexical analyzer to express the number.  If the
 token type is an identifier, that identifier is defined by Bison as a C
 macro whose definition is the appropriate number.  In this example,
@@ -1082,8 +1108,8 @@ Here is the code for the lexical analyzer:
 @example
 @group
 /* 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
+   number on the stack and the token NUM, or the numeric code
+   of the character read if not a number.  Skips all blanks
    and tabs, returns 0 for EOF. */
 
 #include <ctype.h>
@@ -1204,19 +1230,19 @@ Here is how to compile and run the parser file:
 @example
 @group
 # @r{List files in current directory.}
-% ls
+$ @kbd{ls}
 rpcalc.tab.c  rpcalc.y
 @end group
 
 @group
 # @r{Compile the Bison parser.}
 # @r{@samp{-lm} tells compiler to search math library for @code{pow}.}
-% cc rpcalc.tab.c -lm -o rpcalc
+$ @kbd{cc rpcalc.tab.c -lm -o rpcalc}
 @end group
 
 @group
 # @r{List files again.}
-% ls
+$ @kbd{ls}
 rpcalc  rpcalc.tab.c  rpcalc.y
 @end group
 @end example
@@ -1225,19 +1251,19 @@ The file @file{rpcalc} now contains the executable code.  Here is an
 example session using @code{rpcalc}.
 
 @example
-% rpcalc
-4 9 +
+$ @kbd{rpcalc}
+@kbd{4 9 +}
 13
-3 7 + 3 4 5 *+-
+@kbd{3 7 + 3 4 5 *+-}
 -13
-3 7 + 3 4 5 * + - n              @r{Note the unary minus, @samp{n}}
+@kbd{3 7 + 3 4 5 * + - n}              @r{Note the unary minus, @samp{n}}
 13
-5 6 / 4 n +
+@kbd{5 6 / 4 n +}
 -3.166666667
-3 4 ^                            @r{Exponentiation}
+@kbd{3 4 ^}                            @r{Exponentiation}
 81
-^D                               @r{End-of-file indicator}
-%
+@kbd{^D}                               @r{End-of-file indicator}
+$
 @end example
 
 @node Infix Calc
@@ -1306,23 +1332,25 @@ Operator precedence is determined by the line ordering of the
 declarations; the higher the line number of the declaration (lower on
 the page or screen), the higher the precedence.  Hence, exponentiation
 has the highest precedence, unary minus (@code{NEG}) is next, followed
-by @samp{*} and @samp{/}, and so on.  @xref{Precedence, ,Operator Precedence}.
+by @samp{*} and @samp{/}, and so on.  @xref{Precedence, ,Operator
+Precedence}.
 
-The other important new feature is the @code{%prec} in the grammar section
-for the unary minus operator.  The @code{%prec} simply instructs Bison that
-the rule @samp{| '-' exp} has the same precedence as @code{NEG}---in this
-case the next-to-highest.  @xref{Contextual Precedence, ,Context-Dependent Precedence}.
+The other important new feature is the @code{%prec} in the grammar
+section for the unary minus operator.  The @code{%prec} simply instructs
+Bison that the rule @samp{| '-' exp} has the same precedence as
+@code{NEG}---in this case the next-to-highest.  @xref{Contextual
+Precedence, ,Context-Dependent Precedence}.
 
 Here is a sample run of @file{calc.y}:
 
 @need 500
 @example
-% calc
-4 + 4.5 - (34/(8*3+-3))
+$ @kbd{calc}
+@kbd{4 + 4.5 - (34/(8*3+-3))}
 6.880952381
--56 + 2
+@kbd{-56 + 2}
 -54
-3 ^ 2
+@kbd{3 ^ 2}
 9
 @end example
 
@@ -1358,7 +1386,7 @@ 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
+misprint.
 
 This form of error recovery deals with syntax errors.  There are other
 kinds of errors; for example, division by zero, which raises an exception
@@ -1374,13 +1402,11 @@ Bison programs.
 @cindex @code{ltcalc}
 @cindex calculator, location tracking
 
-This example extends the infix notation calculator with location tracking.
-This feature will be used to improve error reporting, and provide better
-error messages.
-
-For the sake of clarity, we will switch for this example to an integer
-calculator, since most of the work needed to use locations will be done
-in the lexical analyser.
+This example extends the infix notation calculator with location
+tracking.  This feature will be used to improve the error messages.  For
+the sake of clarity, this example is a simple integer calculator, since
+most of the work needed to use locations will be done in the lexical
+analyser.
 
 @menu
 * Decls: Ltcalc Decls.  Bison and C declarations for ltcalc.
@@ -1391,8 +1417,8 @@ in the lexical analyser.
 @node Ltcalc Decls
 @subsection Declarations for @code{ltcalc}
 
-The C and Bison declarations for the location tracking calculator are the same
-as the declarations for the infix notation calculator.
+The C and Bison declarations for the location tracking calculator are
+the same as the declarations for the infix notation calculator.
 
 @example
 /* Location tracking calculator.  */
@@ -1413,22 +1439,24 @@ as the declarations for the infix notation calculator.
 %% /* Grammar follows */
 @end example
 
-In the code above, there are no declarations specific to locations.  Defining
-a data type for storing locations is not needed: we will use the type provided
-by default (@pxref{Location Type, ,Data Types of Locations}), which is a four
-member structure with the following integer fields: @code{first_line},
-@code{first_column}, @code{last_line} and @code{last_column}.
+@noindent
+Note there are no declarations specific to locations.  Defining a data
+type for storing locations is not needed: we will use the type provided
+by default (@pxref{Location Type, ,Data Types of Locations}), which is a
+four member structure with the following integer fields:
+@code{first_line}, @code{first_column}, @code{last_line} and
+@code{last_column}.
 
 @node Ltcalc Rules
 @subsection Grammar Rules for @code{ltcalc}
 
-Whether you choose to handle locations or not has no effect on the syntax of
-your language.  Therefore, grammar rules for this example will be very close to
-those of the previous example: we will only modify them to benefit from the new
-informations we will have.
+Whether handling locations or not has no effect on the syntax of your
+language.  Therefore, grammar rules for this example will be very close
+to those of the previous example: we will only modify them to benefit
+from the new information.
 
-Here, we will use locations to report divisions by zero, and locate the wrong
-expressions or subexpressions.
+Here, we will use locations to report divisions by zero, and locate the
+wrong expressions or subexpressions.
 
 @example
 @group
@@ -1449,17 +1477,17 @@ exp     : NUM           @{ $$ = $1; @}
         | exp '-' exp   @{ $$ = $1 - $3; @}
         | exp '*' exp   @{ $$ = $1 * $3; @}
 @end group
-        | exp '/' exp
 @group
+        | exp '/' exp
             @{
               if ($3)
                 $$ = $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);
+                  fprintf (stderr, "%d.%d-%d.%d: division by zero",
+                           @@3.first_line, @@3.first_column,
+                           @@3.last_line, @@3.last_column);
                 @}
             @}
 @end group
@@ -1474,25 +1502,24 @@ This code shows how to reach locations inside of semantic actions, by
 using the pseudo-variables @code{@@@var{n}} for rule components, and the
 pseudo-variable @code{@@$} for groupings.
 
-In this example, we never assign a value to @code{@@$}, because the
-output parser can do this automatically.  By default, before executing
-the C code of each action, @code{@@$} is set to range from the beginning
-of @code{@@1} to the end of @code{@@@var{n}}, for a rule with @var{n}
-components.
-
-Of course, this behavior can be redefined (@pxref{Location Default
-Action, , Default Action for Locations}), and for very specific rules,
-@code{@@$} can be computed by hand.
+We don't need to assign a value to @code{@@$}: the output parser does it
+automatically.  By default, before executing the C code of each action,
+@code{@@$} is set to range from the beginning of @code{@@1} to the end
+of @code{@@@var{n}}, for a rule with @var{n} components.  This behavior
+can be redefined (@pxref{Location Default Action, , Default Action for
+Locations}), and for very specific rules, @code{@@$} can be computed by
+hand.
 
 @node Ltcalc Lexer
 @subsection The @code{ltcalc} Lexical Analyzer.
 
-Until now, we relied on Bison's defaults to enable location tracking. The next
-step is to rewrite the lexical analyser, and make it able to feed the parser
-with locations of tokens, as he already does for semantic values.
+Until now, we relied on Bison's defaults to enable location
+tracking. The next step is to rewrite the lexical analyser, and make it
+able to feed the parser with the token locations, as it already does for
+semantic values.
 
-To do so, we must take into account every single character of the input text,
-to avoid the computed locations of being fuzzy or wrong:
+To this end, we must take into account every single character of the
+input text, to avoid the computed locations of being fuzzy or wrong:
 
 @example
 @group
@@ -1542,17 +1569,18 @@ yylex (void)
 @}
 @end example
 
-Basically, the lexical analyzer does the same processing as before: it skips
-blanks and tabs, and reads numbers or single-character tokens.  In addition
-to this, it updates the @code{yylloc} global variable (of type @code{YYLTYPE}),
-where the location of tokens is stored.
+Basically, the lexical analyzer performs the same processing as before:
+it skips blanks and tabs, and reads numbers or single-character tokens.
+In addition, it updates @code{yylloc}, the global variable (of type
+@code{YYLTYPE}) containing the token's location.
 
-Now, each time this function returns a token, the parser has it's number as
-well as it's semantic value, and it's position in the text. The last needed
-change is to initialize @code{yylloc}, for example in the controlling
-function:
+Now, each time this function returns a token, the parser has its number
+as well as its semantic value, and its location in the text. The last
+needed change is to initialize @code{yylloc}, for example in the
+controlling function:
 
 @example
+@group
 int
 main (void)
 @{
@@ -1560,11 +1588,12 @@ main (void)
   yylloc.first_column = yylloc.last_column = 0;
   return yyparse ();
 @}
+@end group
 @end example
 
-Remember that computing locations is not a matter of syntax.  Every character
-must be associated to a location update, whether it is in valid input, in
-comments, in literal strings, and so on...
+Remember that computing locations is not a matter of syntax.  Every
+character must be associated to a location update, whether it is in
+valid input, in comments, in literal strings, and so on.
 
 @node Multi-function Calc
 @section Multi-Function Calculator: @code{mfcalc}
@@ -1594,20 +1623,20 @@ to create named variables, store values in them, and use them later.
 Here is a sample session with the multi-function calculator:
 
 @example
-% mfcalc
-pi = 3.141592653589
+$ @kbd{mfcalc}
+@kbd{pi = 3.141592653589}
 3.1415926536
-sin(pi)
+@kbd{sin(pi)}
 0.0000000000
-alpha = beta1 = 2.3
+@kbd{alpha = beta1 = 2.3}
 2.3000000000
-alpha
+@kbd{alpha}
 2.3000000000
-ln(alpha)
+@kbd{ln(alpha)}
 0.8329091229
-exp(ln(beta1))
+@kbd{exp(ln(beta1))}
 2.3000000000
-%
+$
 @end example
 
 Note that multiple assignment and nested function calls are permitted.
@@ -1663,11 +1692,12 @@ are @code{NUM}, @code{VAR}, @code{FNCT}, and @code{exp}.  Their
 declarations are augmented with information about their data type (placed
 between angle brackets).
 
-The Bison construct @code{%type} is used for declaring nonterminal symbols,
-just as @code{%token} is used for declaring token types.  We have not used
-@code{%type} before because nonterminal symbols are normally declared
-implicitly by the rules that define them.  But @code{exp} must be declared
-explicitly so we can specify its value type.  @xref{Type Decl, ,Nonterminal Symbols}.
+The Bison construct @code{%type} is used for declaring nonterminal
+symbols, just as @code{%token} is used for declaring token types.  We
+have not used @code{%type} before because nonterminal symbols are
+normally declared implicitly by the rules that define them.  But
+@code{exp} must be declared explicitly so we can specify its value type.
+@xref{Type Decl, ,Nonterminal Symbols}.
 
 @node Mfcalc Rules
 @subsection Grammar Rules for @code{mfcalc}
@@ -1855,7 +1885,7 @@ the name appears in the table, a pointer to its location and its type
 (@code{VAR} or @code{FNCT}) is returned to @code{yyparse}.  If it is not
 already in the table, then it is installed as a @code{VAR} using
 @code{putsym}.  Again, a pointer and its type (which must be @code{VAR}) is
-returned to @code{yyparse}.@refill
+returned to @code{yyparse}.
 
 No change is needed in the handling of numeric values and arithmetic
 operators in @code{yylex}.
@@ -1941,8 +1971,8 @@ yylex (void)
 @end smallexample
 
 This program is both powerful and flexible. You may easily add new
-functions, and it is a simple job to modify this code to install predefined
-variables such as @code{pi} or @code{e} as well.
+functions, and it is a simple job to modify this code to install
+predefined variables such as @code{pi} or @code{e} as well.
 
 @node Exercises
 @section Exercises
@@ -2017,7 +2047,7 @@ Comments enclosed in @samp{/* @dots{} */} may appear in any of the sections.
 @cindex Prologue
 @cindex declarations
 
-The @var{prologue} 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
@@ -2025,6 +2055,33 @@ 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.
 
+You may have more than one @var{Prologue} section, intermixed with the
+@var{Bison declarations}.  This allows you to have C and Bison
+declarations that refer to each other.  For example, the @code{%union}
+declaration may use types defined in a header file, and you may wish to
+prototype functions that take arguments of type @code{YYSTYPE}.  This
+can be done with two @var{Prologue} blocks, one before and one after the
+@code{%union} declaration.
+
+@smallexample
+%@{
+#include <stdio.h>
+#include "ptypes.h"
+%@}
+
+%union @{
+  long n;
+  tree t;  /* @r{@code{tree} is defined in @file{ptypes.h}.} */
+@}
+
+%@{
+static void yyprint(FILE *, int, YYSTYPE);
+#define YYPRINT(F, N, L) yyprint(F, N, L)
+%@}
+
+@dots{}
+@end smallexample
+
 @node Bison Declarations
 @subsection The Bison Declarations Section
 @cindex Bison declarations (introduction)
@@ -2053,8 +2110,8 @@ if it is the first thing in the file.
 @cindex epilogue
 @cindex C code, section for additional
 
-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
+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.
@@ -2122,7 +2179,7 @@ your program will confuse other readers.
 
 All the usual escape sequences used in character literals in C can be
 used in Bison as well, but you must not use the null character as a
-character literal because its ASCII code, zero, is the code @code{yylex}
+character literal because its numeric code, zero, is the code @code{yylex}
 returns for end-of-input (@pxref{Calling Convention, ,Calling Convention
 for @code{yylex}}).
 
@@ -2163,7 +2220,7 @@ on when the parser function returns that symbol.
 The value returned by @code{yylex} is always one of the terminal symbols
 (or 0 for end-of-input).  Whichever way you write the token type in the
 grammar rules, you write it the same way in the definition of @code{yylex}.
-The numeric code for a character token type is simply the ASCII code for
+The numeric code for a character token type is simply the numeric code of
 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.
@@ -2176,9 +2233,25 @@ option when you run Bison, so that it will write these macro definitions
 into a separate header file @file{@var{name}.tab.h} which you can include
 in the other source files that need it.  @xref{Invocation, ,Invoking Bison}.
 
+The @code{yylex} function must use the same character set and encoding
+that was used by Bison.  For example, if you run Bison in an
+@sc{ascii} environment, but then compile and run the resulting program
+in an environment that uses an incompatible character set like
+@sc{ebcdic}, the resulting program will probably not work because the
+tables generated by Bison will assume @sc{ascii} numeric values for
+character tokens.  Portable grammars should avoid non-@sc{ascii}
+character tokens, as implementations in practice often use different
+and incompatible extensions in this area.  However, it is standard
+practice for software distributions to contain C source files that
+were generated by Bison in an @sc{ascii} environment, so installers on
+platforms that are incompatible with @sc{ascii} must rebuild those
+files before compiling them.
+
 The symbol @code{error} is a terminal symbol reserved for error recovery
 (@pxref{Error Recovery}); you shouldn't use it for any other purpose.
-In particular, @code{yylex} should never return this value.
+In particular, @code{yylex} should never return this value.  The default
+value of the error token is 256, unless you explicitly assigned 256 to
+one of your tokens with a @code{%token} declaration.
 
 @node Rules
 @section Syntax of Grammar Rules
@@ -2309,14 +2382,14 @@ expseq1:  exp
 @end example
 
 @noindent
-Any kind of sequence can be defined using either left recursion or
-right recursion, but you should always use left recursion, because it
-can parse a sequence of any number of elements with bounded stack
-space.  Right recursion uses up space on the Bison stack in proportion
-to the number of elements in the sequence, because all the elements
-must be shifted onto the stack before the rule can be applied even
-once.  @xref{Algorithm, ,The Bison Parser Algorithm }, for
-further explanation of this.
+Any kind of sequence can be defined using either left recursion or right
+recursion, but you should always use left recursion, because it can
+parse a sequence of any number of elements with bounded stack space.
+Right recursion uses up space on the Bison stack in proportion to the
+number of elements in the sequence, because all the elements must be
+shifted onto the stack before the rule can be applied even once.
+@xref{Algorithm, ,The Bison Parser Algorithm}, for further explanation
+of this.
 
 @cindex mutual recursion
 @dfn{Indirect} or @dfn{mutual} recursion occurs when the result of the
@@ -2405,7 +2478,8 @@ requires you to do two things:
 @itemize @bullet
 @item
 Specify the entire collection of possible data types, with the
-@code{%union} Bison declaration (@pxref{Union Decl, ,The Collection of Value Types}).
+@code{%union} Bison declaration (@pxref{Union Decl, ,The Collection of
+Value Types}).
 
 @item
 Choose one of those types for each symbol (terminal or nonterminal) for
@@ -2427,10 +2501,11 @@ is to compute a semantic value for the grouping built by the rule from the
 semantic values associated with tokens or smaller groupings.
 
 An action consists of C statements surrounded by braces, much like a
-compound statement in C.  It can be placed at any position in the rule; it
-is executed at that position.  Most rules have just one action at the end
-of the rule, following all the components.  Actions in the middle of a rule
-are tricky and used only for special purposes (@pxref{Mid-Rule Actions, ,Actions in Mid-Rule}).
+compound statement in C.  It can be placed at any position in the rule;
+it is executed at that position.  Most rules have just one action at the
+end of the rule, following all the components.  Actions in the middle of
+a rule are tricky and used only for special purposes (@pxref{Mid-Rule
+Actions, ,Actions in Mid-Rule}).
 
 The C code in an action can refer to the semantic values of the components
 matched by the rule with the construct @code{$@var{n}}, which stands for
@@ -2457,7 +2532,19 @@ which are the first and third symbols on the right hand side of the rule.
 The sum is stored into @code{$$} so that it becomes the semantic value of
 the addition-expression just recognized by the rule.  If there were a
 useful semantic value associated with the @samp{+} token, it could be
-referred to as @code{$2}.@refill
+referred to as @code{$2}.
+
+Note that the vertical-bar character @samp{|} is really a rule
+separator, and actions are attached to a single rule.  This is a
+difference with tools like Flex, for which @samp{|} stands for either
+``or'', or ``the same action as that of the next rule''.  In the
+following example, the action is triggered only when @samp{b} is found:
+
+@example
+@group
+a-or-b: 'a'|'b'   @{ a_or_b_found = 1; @};
+@end group
+@end example
 
 @cindex default action
 If you don't specify an action for a rule, Bison supplies a default:
@@ -2503,7 +2590,7 @@ If you have used @code{%union} to specify a variety of data types, then you
 must declare a choice among these types for each terminal or nonterminal
 symbol that can have a semantic value.  Then each time you use @code{$$} or
 @code{$@var{n}}, its data type is determined by which symbol it refers to
-in the rule.  In this example,@refill
+in the rule.  In this example,
 
 @example
 @group
@@ -2517,7 +2604,7 @@ exp:    @dots{}
 @code{$1} and @code{$3} refer to instances of @code{exp}, so they all
 have the data type declared for the nonterminal symbol @code{exp}.  If
 @code{$2} were used, it would have the data type declared for the
-terminal symbol @code{'+'}, whatever that might be.@refill
+terminal symbol @code{'+'}, whatever that might be.
 
 Alternatively, you can specify the data type when you refer to the value,
 by inserting @samp{<@var{type}>} after the @samp{$} at the beginning of the
@@ -2710,8 +2797,8 @@ 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.
+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.
@@ -2812,11 +2899,11 @@ exp:    @dots{}
 @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.
+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 invoked 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.
@@ -2830,9 +2917,11 @@ 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;
+#define YYLLOC_DEFAULT(Current, Rhs, N)          \
+  Current.first_line   = Rhs[1].first_line;      \
+  Current.first_column = Rhs[1].first_column;    \
+  Current.last_line    = Rhs[N].last_line;       \
+  Current.last_column  = Rhs[N].last_column;
 @end group
 @end example
 
@@ -2844,12 +2933,8 @@ 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}.
+For consistency with semantic actions, valid indexes for the location
+array range from 1 to @var{n}.
 @end itemize
 
 @node Declarations
@@ -2868,7 +2953,8 @@ value (@pxref{Multiple Types, ,More Than One Value Type}).
 
 The first rule in the file also specifies the start symbol, by default.
 If you want some other symbol to be the start symbol, you must declare
-it explicitly (@pxref{Language and Grammar, ,Languages and Context-Free Grammars}).
+it explicitly (@pxref{Language and Grammar, ,Languages and Context-Free
+Grammars}).
 
 @menu
 * Token Decl::        Declaring terminal symbols.
@@ -2913,11 +2999,12 @@ an integer value in the field immediately following the token name:
 @noindent
 It is generally best, however, to let Bison choose the numeric codes for
 all token types.  Bison will automatically select codes that don't conflict
-with each other or with ASCII characters.
+with each other or with normal 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
-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:
 
@@ -2964,7 +3051,8 @@ obtain the token type code number (@pxref{Calling Convention}).
 Use the @code{%left}, @code{%right} or @code{%nonassoc} declaration to
 declare a token and specify its precedence and associativity, all at
 once.  These are called @dfn{precedence declarations}.
-@xref{Precedence, ,Operator Precedence}, for general information on operator precedence.
+@xref{Precedence, ,Operator Precedence}, for general information on
+operator precedence.
 
 The syntax of a precedence declaration is the same as that of
 @code{%token}: either
@@ -3051,11 +3139,12 @@ used.  This is done with a @code{%type} declaration, like this:
 @end example
 
 @noindent
-Here @var{nonterminal} is the name of a nonterminal symbol, and @var{type}
-is the name given in the @code{%union} to the alternative that you want
-(@pxref{Union Decl, ,The Collection of Value Types}).  You can give any number of nonterminal symbols in
-the same @code{%type} declaration, if they have the same value type.  Use
-spaces to separate the symbol names.
+Here @var{nonterminal} is the name of a nonterminal symbol, and
+@var{type} is the name given in the @code{%union} to the alternative
+that you want (@pxref{Union Decl, ,The Collection of Value Types}).  You
+can give any number of nonterminal symbols in the same @code{%type}
+declaration, if they have the same value type.  Use spaces to separate
+the symbol names.
 
 You can also declare the value type of a terminal symbol.  To do this,
 use the same @code{<@var{type}>} construction in a declaration for the
@@ -3130,7 +3219,7 @@ may override this restriction with the @code{%start} declaration as follows:
 @subsection A Pure (Reentrant) Parser
 @cindex reentrant parser
 @cindex pure parser
-@findex %pure_parser
+@findex %pure-parser
 
 A @dfn{reentrant} program is one which does not alter in the course of
 execution; in other words, it consists entirely of @dfn{pure} (read-only)
@@ -3146,11 +3235,11 @@ statically allocated variables for communication with @code{yylex},
 including @code{yylval} and @code{yylloc}.)
 
 Alternatively, you can generate a pure, reentrant parser.  The Bison
-declaration @code{%pure_parser} says that you want the parser to be
+declaration @code{%pure-parser} says that you want the parser to be
 reentrant.  It looks like this:
 
 @example
-%pure_parser
+%pure-parser
 @end example
 
 The result is that the communication variables @code{yylval} and
@@ -3216,9 +3305,9 @@ directives:
 
 @table @code
 @item %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}.
+In the parser file, define the macro @code{YYDEBUG} to 1 if it is not
+already defined, so that the debugging facilities are compiled.
+@xref{Tracing, ,Tracing Your Parser}.
 
 @item %defines
 Write an extra output file containing macro definitions for the token
@@ -3226,23 +3315,23 @@ type names defined in the grammar and the semantic value type
 @code{YYSTYPE}, as well as a few @code{extern} variable declarations.
 
 If the parser output file is named @file{@var{name}.c} then this file
-is named @file{@var{name}.h}.@refill
+is named @file{@var{name}.h}.
 
 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
+@code{yylval}.  @xref{Token Values, ,Semantic Values of Tokens}.
 
 @item %file-prefix="@var{prefix}"
 Specify a prefix to use for all Bison output file names.  The names are
 chosen as if the input file were named @file{@var{prefix}.y}.
 
-@c @item %header_extension
+@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 grammar file named @file{foo.ypp} and containing a
-@c @code{%header_extension .hh} directive will produce a header file
+@c @code{%header-extension .hh} directive will produce a header file
 @c named @file{foo.tab.hh}
 
 @item %locations
@@ -3256,10 +3345,10 @@ accurate parse error messages.
 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{%name-prefix="c_"}, the names become @code{c_parse},
-@code{c_lex}, and so on.  @xref{Multiple Parsers, ,Multiple Parsers in
-the Same Program}.
+@code{yylval}, @code{yychar}, @code{yydebug}, and possible
+@code{yylloc}.  For example, if you use @samp{%name-prefix="c_"}, the
+names become @code{c_parse}, @code{c_lex}, and so on.  @xref{Multiple
+Parsers, ,Multiple Parsers in the Same Program}.
 
 @item %no-parser
 Do not include any C code in the parser file; generate tables only.  The
@@ -3285,14 +3374,14 @@ Specify the @var{filename} for the parser file.
 Request a pure (reentrant) parser program (@pxref{Pure Decl, ,A Pure
 (Reentrant) Parser}).
 
-@c @item %source_extension
+@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 @code{%source-extension .cpp} directive will produce a parser file
 @c named @file{foo.tab.cpp}
 
-@item %token_table
+@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
 token whose internal Bison token code number is @var{i}.  The first three
@@ -3310,7 +3399,7 @@ consists of three characters @samp{*"*}, its string in @code{yytname}
 contains @samp{"*"*"}.  (In C, that would be written as
 @code{"\"*\"*\""}).
 
-When you specify @code{%token_table}, Bison also generates macro
+When you specify @code{%token-table}, Bison also generates macro
 definitions for macros @code{YYNTOKENS}, @code{YYNNTS}, and
 @code{YYNRULES}, and @code{YYNSTATES}:
 
@@ -3328,20 +3417,12 @@ The number of parser states (@pxref{Parser States}).
 @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
-that state.
+that state. @xref{Understanding, , Understanding Your Parser}, for more
+information.
 
-This file also describes all the conflicts, both those resolved by
-operator precedence and the unresolved ones.
 
-The file's name is made by removing @samp{.tab.c} or @samp{.c} from
-the parser output file name, and adding @samp{.output} instead.@refill
-
-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
 
 @item %yacc
-@itemx %fixed-output-files
 Pretend the option @option{--yacc} was given, i.e., imitate Yacc,
 including its naming conventions.  @xref{Bison Options}, for more.
 @end table
@@ -3358,10 +3439,10 @@ language with the same program?  Then you need to avoid a name conflict
 between different definitions of @code{yyparse}, @code{yylval}, and so on.
 
 The easy way to do this is to use the option @samp{-p @var{prefix}}
-(@pxref{Invocation, ,Invoking Bison}).  This renames the interface functions and
-variables of the Bison parser to start with @var{prefix} instead of
-@samp{yy}.  You can use this to give each parser distinct names that do
-not conflict.
+(@pxref{Invocation, ,Invoking Bison}).  This renames the interface
+functions and variables of the Bison parser to start with @var{prefix}
+instead of @samp{yy}.  You can use this to give each parser distinct
+names that do not conflict.
 
 The precise list of symbols renamed is @code{yyparse}, @code{yylex},
 @code{yyerror}, @code{yynerrs}, @code{yylval}, @code{yychar} and
@@ -3445,7 +3526,7 @@ need to arrange for the token-type macro definitions to be available there.
 To do this, use the @samp{-d} option when you run Bison, so that it will
 write these macro definitions into a separate header file
 @file{@var{name}.tab.h} which you can include in the other source files
-that need it.  @xref{Invocation, ,Invoking Bison}.@refill
+that need it.  @xref{Invocation, ,Invoking Bison}.
 
 @menu
 * Calling Convention::  How @code{yyparse} calls @code{yylex}.
@@ -3532,7 +3613,7 @@ for (i = 0; i < YYNTOKENS; i++)
 @end smallexample
 
 The @code{yytname} table is generated only if you use the
-@code{%token_table} declaration.  @xref{Decl Summary}.
+@code{%token-table} declaration.  @xref{Decl Summary}.
 @end itemize
 
 @node Token Values
@@ -3555,9 +3636,10 @@ Thus, if the type is @code{int} (the default), you might write this in
 @end example
 
 When you are using multiple data types, @code{yylval}'s type is a union
-made from the @code{%union} declaration (@pxref{Union Decl, ,The Collection of Value Types}).  So when
-you store a token's value, you must use the proper member of the union.
-If the @code{%union} declaration looks like this:
+made from the @code{%union} declaration (@pxref{Union Decl, ,The
+Collection of Value Types}).  So when you store a token's value, you
+must use the proper member of the union.  If the @code{%union}
+declaration looks like this:
 
 @example
 @group
@@ -3605,7 +3687,7 @@ The data type of @code{yylloc} has the name @code{YYLTYPE}.
 @node Pure Calling
 @subsection Calling Conventions for Pure Parsers
 
-When you use the Bison declaration @code{%pure_parser} to request a
+When you use the Bison declaration @code{%pure-parser} to request a
 pure, reentrant parser, the global communication variables @code{yylval}
 and @code{yylloc} cannot be used.  (@xref{Pure Decl, ,A Pure (Reentrant)
 Parser}.)  In such parsers the two global variables are replaced by
@@ -3705,7 +3787,7 @@ arguments in total, depending on whether an argument of type
 the proper object type, or you can declare it as @code{void *} and
 access the contents as shown above.
 
-You can use @samp{%pure_parser} to request a reentrant parser without
+You can use @samp{%pure-parser} to request a reentrant parser without
 also using @code{YYPARSE_PARAM}.  Then you should call @code{yyparse}
 with no arguments, as usual.
 
@@ -3766,8 +3848,8 @@ immediately return 1.
 @vindex yynerrs
 The variable @code{yynerrs} contains the number of syntax errors
 encountered so far.  Normally this variable is global; but if you
-request a pure parser (@pxref{Pure Decl, ,A Pure (Reentrant) Parser}) then it is a local variable
-which only the actions can access.
+request a pure parser (@pxref{Pure Decl, ,A Pure (Reentrant) Parser})
+then it is a local variable which only the actions can access.
 
 @node Action Features
 @section Special Features for Use in Actions
@@ -3788,12 +3870,13 @@ Acts like a variable that contains the semantic value for the
 
 @item $<@var{typealt}>$
 Like @code{$$} but specifies alternative @var{typealt} in the union
-specified by the @code{%union} declaration.  @xref{Action Types, ,Data Types of Values in Actions}.
+specified by the @code{%union} declaration.  @xref{Action Types, ,Data
+Types of Values in Actions}.
 
 @item $<@var{typealt}>@var{n}
 Like @code{$@var{n}} but specifies alternative @var{typealt} in the
 union specified by the @code{%union} declaration.
-@xref{Action Types, ,Data Types of Values in Actions}.@refill
+@xref{Action Types, ,Data Types of Values in Actions}.
 
 @item YYABORT;
 Return immediately from @code{yyparse}, indicating failure.
@@ -4217,18 +4300,19 @@ and therefore are represented by names, not character literals.)
 
 The first effect of the precedence declarations is to assign precedence
 levels to the terminal symbols declared.  The second effect is to assign
-precedence levels to certain rules: each rule gets its precedence from the
-last terminal symbol mentioned in the components.  (You can also specify
-explicitly the precedence of a rule.  @xref{Contextual Precedence, ,Context-Dependent Precedence}.)
-
-Finally, the resolution of conflicts works by comparing the
-precedence of the rule being considered with that of the
-look-ahead token.  If the token's precedence is higher, the
-choice is to shift.  If the rule's precedence is higher, the
-choice is to reduce.  If they have equal precedence, the choice
-is made based on the associativity of that precedence level.  The
-verbose output file made by @samp{-v} (@pxref{Invocation, ,Invoking Bison}) says
-how each conflict was resolved.
+precedence levels to certain rules: each rule gets its precedence from
+the last terminal symbol mentioned in the components.  (You can also
+specify explicitly the precedence of a rule.  @xref{Contextual
+Precedence, ,Context-Dependent Precedence}.)
+
+Finally, the resolution of conflicts works by comparing the precedence
+of the rule being considered with that of the look-ahead token.  If the
+token's precedence is higher, the choice is to shift.  If the rule's
+precedence is higher, the choice is to reduce.  If they have equal
+precedence, the choice is made based on the associativity of that
+precedence level.  The verbose output file made by @samp{-v}
+(@pxref{Invocation, ,Invoking Bison}) says how each conflict was
+resolved.
 
 Not all rules and not all tokens have precedence.  If either the rule or
 the look-ahead token has no precedence, then the default is to shift.
@@ -4250,7 +4334,7 @@ The Bison precedence declarations, @code{%left}, @code{%right} and
 @code{%nonassoc}, can only be used once for a given token; so a token has
 only one precedence declared in this way.  For context-dependent
 precedence, you need to use an additional mechanism: the @code{%prec}
-modifier for rules.@refill
+modifier for rules.
 
 The @code{%prec} modifier declares the precedence of a particular rule by
 specifying a terminal symbol whose precedence should be used for that rule.
@@ -4894,9 +4978,414 @@ make sure your error recovery rules are not of this kind.  Each rule must
 be such that you can be sure that it always will, or always won't, have to
 clear the flag.
 
+@c ================================================== Debugging Your Parser
+
 @node Debugging
 @chapter Debugging Your Parser
-@findex YYDEBUG
+
+Developing a parser can be a challenge, especially if you don't
+understand the algorithm (@pxref{Algorithm, ,The Bison Parser
+Algorithm}).  Even so, sometimes a detailed description of the automaton
+can help (@pxref{Understanding, , Understanding Your Parser}), or
+tracing the execution of the parser can give some insight on why it
+behaves improperly (@pxref{Tracing, , Tracing Your Parser}).
+
+@menu
+* Understanding::     Understanding the structure of your parser.
+* Tracing::           Tracing the execution of your parser.
+@end menu
+
+@node Understanding
+@section Understanding Your Parser
+
+As documented elsewhere (@pxref{Algorithm, ,The Bison Parser Algorithm})
+Bison parsers are @dfn{shift/reduce automata}.  In some cases (much more
+frequent than one would hope), looking at this automaton is required to
+tune or simply fix a parser.  Bison provides two different
+representation of it, either textually or graphically (as a @sc{vcg}
+file).
+
+The textual file is generated when the options @option{--report} or
+@option{--verbose} are specified, see @xref{Invocation, , Invoking
+Bison}.  Its name is made by removing @samp{.tab.c} or @samp{.c} from
+the parser output file name, and adding @samp{.output} instead.
+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}.
+
+The following grammar file, @file{calc.y}, will be used in the sequel:
+
+@example
+%token NUM STR
+%left '+' '-'
+%left '*'
+%%
+exp: exp '+' exp
+   | exp '-' exp
+   | exp '*' exp
+   | exp '/' exp
+   | NUM
+   ;
+useless: STR;
+%%
+@end example
+
+@command{bison} reports that @samp{calc.y contains 1 useless nonterminal
+and 1 useless rule} and that @samp{calc.y contains 7 shift/reduce
+conflicts}.  When given @option{--report=state}, in addition to
+@file{calc.tab.c}, it creates a file @file{calc.output} with contents
+detailed below.  The order of the output and the exact presentation
+might vary, but the interpretation is the same.
+
+The first section includes details on conflicts that were solved thanks
+to precedence and/or associativity:
+
+@example
+Conflict in state 8 between rule 2 and token '+' resolved as reduce.
+Conflict in state 8 between rule 2 and token '-' resolved as reduce.
+Conflict in state 8 between rule 2 and token '*' resolved as shift.
+@exdent @dots{}
+@end example
+
+@noindent
+The next section lists states that still have conflicts.
+
+@example
+State 8 contains 1 shift/reduce conflict.
+State 9 contains 1 shift/reduce conflict.
+State 10 contains 1 shift/reduce conflict.
+State 11 contains 4 shift/reduce conflicts.
+@end example
+
+@noindent
+@cindex token, useless
+@cindex useless token
+@cindex nonterminal, useless
+@cindex useless nonterminal
+@cindex rule, useless
+@cindex useless rule
+The next section reports useless tokens, nonterminal and rules.  Useless
+nonterminals and rules are removed in order to produce a smaller parser,
+but useless tokens are preserved, since they might be used by the
+scanner (note the difference between ``useless'' and ``not used''
+below):
+
+@example
+Useless nonterminals:
+   useless
+
+Terminals which are not used:
+   STR
+
+Useless rules:
+#6     useless: STR;
+@end example
+
+@noindent
+The next section reproduces the exact grammar that Bison used:
+
+@example
+Grammar
+
+  Number, Line, Rule
+    0   5 $axiom -> exp $
+    1   5 exp -> exp '+' exp
+    2   6 exp -> exp '-' exp
+    3   7 exp -> exp '*' exp
+    4   8 exp -> exp '/' exp
+    5   9 exp -> NUM
+@end example
+
+@noindent
+and reports the uses of the symbols:
+
+@example
+Terminals, with rules where they appear
+
+$ (0) 0
+'*' (42) 3
+'+' (43) 1
+'-' (45) 2
+'/' (47) 4
+error (256)
+NUM (258) 5
+
+Nonterminals, with rules where they appear
+
+$axiom (8)
+    on left: 0
+exp (9)
+    on left: 1 2 3 4 5, on right: 0 1 2 3 4
+@end example
+
+@noindent
+@cindex item
+@cindex pointed rule
+@cindex rule, pointed
+Bison then proceeds onto the automaton itself, describing each state
+with it set of @dfn{items}, also known as @dfn{pointed rules}.  Each
+item is a production rule together with a point (marked by @samp{.})
+that the input cursor.
+
+@example
+state 0
+
+    $axiom  ->  . exp $   (rule 0)
+
+    NUM 	shift, and go to state 1
+
+    exp 	go to state 2
+@end example
+
+This reads as follows: ``state 0 corresponds to being at the very
+beginning of the parsing, in the initial rule, right before the start
+symbol (here, @code{exp}).  When the parser returns to this state right
+after having reduced a rule that produced an @code{exp}, the control
+flow jumps to state 2.  If there is no such transition on a nonterminal
+symbol, and the lookahead is a @code{NUM}, then this token is shifted on
+the parse stack, and the control flow jumps to state 1.  Any other
+lookahead triggers a parse error.''
+
+@cindex core, item set
+@cindex item set core
+@cindex kernel, item set
+@cindex item set core
+Even though the only active rule in state 0 seems to be rule 0, the
+report lists @code{NUM} as a lookahead symbol because @code{NUM} can be
+at the beginning of any rule deriving an @code{exp}.  By default Bison
+reports the so-called @dfn{core} or @dfn{kernel} of the item set, but if
+you want to see more detail you can invoke @command{bison} with
+@option{--report=itemset} to list all the items, include those that can
+be derived:
+
+@example
+state 0
+
+    $axiom  ->  . exp $   (rule 0)
+    exp  ->  . exp '+' exp   (rule 1)
+    exp  ->  . exp '-' exp   (rule 2)
+    exp  ->  . exp '*' exp   (rule 3)
+    exp  ->  . exp '/' exp   (rule 4)
+    exp  ->  . NUM   (rule 5)
+
+    NUM         shift, and go to state 1
+
+    exp         go to state 2
+@end example
+
+@noindent
+In the state 1...
+
+@example
+state 1
+
+    exp  ->  NUM .   (rule 5)
+
+    $default	reduce using rule 5 (exp)
+@end example
+
+@noindent
+the rule 5, @samp{exp: NUM;}, is completed.  Whatever the lookahead
+(@samp{$default}), the parser will reduce it.  If it was coming from
+state 0, then, after this reduction it will return to state 0, and will
+jump to state 2 (@samp{exp: go to state 2}).
+
+@example
+state 2
+
+    $axiom  ->  exp . $   (rule 0)
+    exp  ->  exp . '+' exp   (rule 1)
+    exp  ->  exp . '-' exp   (rule 2)
+    exp  ->  exp . '*' exp   (rule 3)
+    exp  ->  exp . '/' exp   (rule 4)
+
+    $   	shift, and go to state 3
+    '+' 	shift, and go to state 4
+    '-' 	shift, and go to state 5
+    '*' 	shift, and go to state 6
+    '/' 	shift, and go to state 7
+@end example
+
+@noindent
+In state 2, the automaton can only shift a symbol.  For instance,
+because of the item @samp{exp -> exp . '+' exp}, if the lookahead if
+@samp{+}, it will be shifted on the parse stack, and the automaton
+control will jump to state 4, corresponding to the item @samp{exp -> exp
+'+' . exp}.  Since there is no default action, any other token than
+those listed above will trigger a parse error.
+
+The state 3 is named the @dfn{final state}, or the @dfn{accepting
+state}:
+
+@example
+state 3
+
+    $axiom  ->  exp $ .   (rule 0)
+
+    $default	accept
+@end example
+
+@noindent
+the initial rule is completed (the start symbol and the end
+of input were read), the parsing exits successfully.
+
+The interpretation of states 4 to 7 is straightforward, and is left to
+the reader.
+
+@example
+state 4
+
+    exp  ->  exp '+' . exp   (rule 1)
+
+    NUM 	shift, and go to state 1
+
+    exp 	go to state 8
+
+state 5
+
+    exp  ->  exp '-' . exp   (rule 2)
+
+    NUM 	shift, and go to state 1
+
+    exp 	go to state 9
+
+state 6
+
+    exp  ->  exp '*' . exp   (rule 3)
+
+    NUM 	shift, and go to state 1
+
+    exp 	go to state 10
+
+state 7
+
+    exp  ->  exp '/' . exp   (rule 4)
+
+    NUM 	shift, and go to state 1
+
+    exp 	go to state 11
+@end example
+
+As was announced in beginning of the report, @samp{State 8 contains 1
+shift/reduce conflict}:
+
+@example
+state 8
+
+    exp  ->  exp . '+' exp   (rule 1)
+    exp  ->  exp '+' exp .   (rule 1)
+    exp  ->  exp . '-' exp   (rule 2)
+    exp  ->  exp . '*' exp   (rule 3)
+    exp  ->  exp . '/' exp   (rule 4)
+
+    '*' 	shift, and go to state 6
+    '/' 	shift, and go to state 7
+
+    '/' 	[reduce using rule 1 (exp)]
+    $default	reduce using rule 1 (exp)
+@end example
+
+Indeed, there are two actions associated to the lookahead @samp{/}:
+either shifting (and going to state 7), or reducing rule 1.  The
+conflict means that either the grammar is ambiguous, or the parser lacks
+information to make the right decision.  Indeed the grammar is
+ambiguous, as, since we did not specify the precedence of @samp{/}, the
+sentence @samp{NUM + NUM / NUM} can be parsed as @samp{NUM + (NUM /
+NUM)}, which corresponds to shifting @samp{/}, or as @samp{(NUM + NUM) /
+NUM}, which corresponds to reducing rule 1.
+
+Because in LALR(1) parsing a single decision can be made, Bison
+arbitrarily chose to disable the reduction, see @ref{Shift/Reduce, ,
+Shift/Reduce Conflicts}.  Discarded actions are reported in between
+square brackets.
+
+Note that all the previous states had a single possible action: either
+shifting the next token and going to the corresponding state, or
+reducing a single rule.  In the other cases, i.e., when shifting
+@emph{and} reducing is possible or when @emph{several} reductions are
+possible, the lookahead is required to select the action.  State 8 is
+one such state: if the lookahead is @samp{*} or @samp{/} then the action
+is shifting, otherwise the action is reducing rule 1.  In other words,
+the first two items, corresponding to rule 1, are not eligible when the
+lookahead is @samp{*}, since we specified that @samp{*} has higher
+precedence that @samp{+}.  More generally, some items are eligible only
+with some set of possible lookaheads.  When run with
+@option{--report=lookahead}, Bison specifies these lookaheads:
+
+@example
+state 8
+
+    exp  ->  exp . '+' exp  [$, '+', '-', '/']   (rule 1)
+    exp  ->  exp '+' exp .  [$, '+', '-', '/']   (rule 1)
+    exp  ->  exp . '-' exp   (rule 2)
+    exp  ->  exp . '*' exp   (rule 3)
+    exp  ->  exp . '/' exp   (rule 4)
+
+    '*'         shift, and go to state 6
+    '/'         shift, and go to state 7
+
+    '/'         [reduce using rule 1 (exp)]
+    $default    reduce using rule 1 (exp)
+@end example
+
+The remaining states are similar:
+
+@example
+state 9
+
+    exp  ->  exp . '+' exp   (rule 1)
+    exp  ->  exp . '-' exp   (rule 2)
+    exp  ->  exp '-' exp .   (rule 2)
+    exp  ->  exp . '*' exp   (rule 3)
+    exp  ->  exp . '/' exp   (rule 4)
+
+    '*' 	shift, and go to state 6
+    '/' 	shift, and go to state 7
+
+    '/' 	[reduce using rule 2 (exp)]
+    $default	reduce using rule 2 (exp)
+
+state 10
+
+    exp  ->  exp . '+' exp   (rule 1)
+    exp  ->  exp . '-' exp   (rule 2)
+    exp  ->  exp . '*' exp   (rule 3)
+    exp  ->  exp '*' exp .   (rule 3)
+    exp  ->  exp . '/' exp   (rule 4)
+
+    '/' 	shift, and go to state 7
+
+    '/' 	[reduce using rule 3 (exp)]
+    $default	reduce using rule 3 (exp)
+
+state 11
+
+    exp  ->  exp . '+' exp   (rule 1)
+    exp  ->  exp . '-' exp   (rule 2)
+    exp  ->  exp . '*' exp   (rule 3)
+    exp  ->  exp . '/' exp   (rule 4)
+    exp  ->  exp '/' exp .   (rule 4)
+
+    '+' 	shift, and go to state 4
+    '-' 	shift, and go to state 5
+    '*' 	shift, and go to state 6
+    '/' 	shift, and go to state 7
+
+    '+' 	[reduce using rule 4 (exp)]
+    '-' 	[reduce using rule 4 (exp)]
+    '*' 	[reduce using rule 4 (exp)]
+    '/' 	[reduce using rule 4 (exp)]
+    $default	reduce using rule 4 (exp)
+@end example
+
+@noindent
+Observe that state 11 contains conflicts due to the lack of precedence
+of @samp{/} wrt @samp{+}, @samp{-}, and @samp{*}, but also because the
+associativity of @samp{/} is not specified.
+
+
+@node Tracing
+@section Tracing Your Parser
 @findex yydebug
 @cindex debugging
 @cindex tracing the parser
@@ -4904,15 +5393,39 @@ clear the flag.
 If a Bison grammar compiles properly but doesn't do what you want when it
 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 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.
+There are several means to enable compilation of trace facilities:
 
-The trace facility uses @code{stderr}, so you must add
-@w{@code{#include <stdio.h>}} to the prologue unless it is already there.
+@table @asis
+@item the macro @code{YYDEBUG}
+@findex YYDEBUG
+Define the macro @code{YYDEBUG} to a nonzero value when you compile the
+parser.  This is compliant with POSIX Yacc.  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}).
+
+@item the option @option{-t}, @option{--debug}
+Use the @samp{-t} option when you run Bison (@pxref{Invocation,
+,Invoking Bison}).  This is POSIX compliant too.
+
+@item the directive @samp{%debug}
+@findex %debug
+Add the @code{%debug} directive (@pxref{Decl Summary, ,Bison
+Declaration Summary}).  This is a Bison extension, which will prove
+useful when Bison will output parsers for languages that don't use a
+preprocessor.  Useless POSIX and Yacc portability matter to you, this is
+the preferred solution.
+@end table
+
+We suggest that you always enable the debug option so that debugging is
+always possible.
+
+The trace facility outputs messages with macro calls of the form
+@code{YYFPRINTF (stderr, @var{format}, @var{args})} where
+@var{format} and @var{args} are the usual @code{printf} format and
+arguments.  If you define @code{YYDEBUG} to a nonzero value but do not
+define @code{YYFPRINTF}, @code{<stdio.h>} is automatically included
+and @code{YYPRINTF} is defined to @code{fprintf}.
 
 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}.
@@ -4937,13 +5450,14 @@ of the state stack afterward.
 @end itemize
 
 To make sense of this information, it helps to refer to the listing file
-produced by the Bison @samp{-v} option (@pxref{Invocation, ,Invoking Bison}).  This file
-shows the meaning of each state in terms of positions in various rules, and
-also what each state will do with each possible input token.  As you read
-the successive trace messages, you can see that the parser is functioning
-according to its specification in the listing file.  Eventually you will
-arrive at the place where something undesirable happens, and you will see
-which parts of the grammar are to blame.
+produced by the Bison @samp{-v} option (@pxref{Invocation, ,Invoking
+Bison}).  This file shows the meaning of each state in terms of
+positions in various rules, and also what each state will do with each
+possible input token.  As you read the successive trace messages, you
+can see that the parser is functioning according to its specification in
+the listing file.  Eventually you will arrive at the place where
+something undesirable happens, and you will see which parts of the
+grammar are to blame.
 
 The parser file is a C program and you can use C debuggers on it, but it's
 not easy to interpret what it is doing.  The parser function is a
@@ -4975,6 +5489,8 @@ yyprint (FILE *file, int type, YYSTYPE value)
 @}
 @end smallexample
 
+@c ================================================= Invoking Bison
+
 @node Invocation
 @chapter Invoking Bison
 @cindex invoking Bison
@@ -4991,7 +5507,7 @@ Here @var{infile} is the grammar file name, which usually ends in
 @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}. It's is also possible, in case you are writting
+@file{hack/foo.tab.c}. It's is also possible, in case you are writing
 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++}).
@@ -5050,12 +5566,11 @@ Print the version number of Bison and exit.
 @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
+for Yacc:
 
 @example
 bison -y $*
@@ -5073,9 +5588,9 @@ you are developing Bison.
 
 @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}.
+In the parser file, define the macro @code{YYDEBUG} to 1 if it is not
+already defined, so that the debugging facilities are compiled.
+@xref{Tracing, ,Tracing Your Parser}.
 
 @item --locations
 Pretend that @code{%locations} was specified.  @xref{Decl Summary}.
@@ -5121,6 +5636,27 @@ Same as above, but save in the file @var{defines-file}.
 Pretend that @code{%verbose} was specified, i.e, specify prefix to use
 for all Bison output file names. @xref{Decl Summary}.
 
+@item -r @var{things}
+@itemx --report=@var{things}
+Write an extra output file containing verbose description of the comma
+separated list of @var{things} among:
+
+@table @code
+@item state
+Description of the grammar, conflicts (resolved and unresolved), and
+LALR automaton.
+
+@item lookahead
+Implies @code{state} and augments the description of the automaton with
+each rule's lookahead set.
+
+@item itemset
+Implies @code{state} and augments the description of the automaton with
+the full set of items for each state, instead of its core only.
+@end table
+
+For instance, on the following grammar
+
 @item -v
 @itemx --verbose
 Pretend that @code{%verbose} was specified, i.e, write an extra output
@@ -5148,7 +5684,6 @@ the output graph filename.
 @node Environment Variables
 @section Environment Variables
 @cindex environment variables
-@cindex BISON_HAIRY
 @cindex BISON_SIMPLE
 
 Here is a list of environment variables which affect the way Bison
@@ -5156,18 +5691,11 @@ 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.
-
 @end table
 
 @node Option Cross Key
@@ -5183,7 +5711,6 @@ the corresponding short option.
 \line{ --debug \leaderfill -t}
 \line{ --defines \leaderfill -d}
 \line{ --file-prefix \leaderfill -b}
-\line{ --fixed-output-files \leaderfill -y}
 \line{ --graph \leaderfill -g}
 \line{ --help \leaderfill -h}
 \line{ --name-prefix \leaderfill -p}
@@ -5202,7 +5729,6 @@ the corresponding short option.
 --debug                               -t
 --defines=@var{defines-file}          -d
 --file-prefix=@var{prefix}                  -b @var{file-prefix}
---fixed-output-files --yacc           -y
 --graph=@var{graph-file}              -d
 --help                                -h
 --name-prefix=@var{prefix}                  -p @var{name-prefix}
@@ -5212,6 +5738,7 @@ the corresponding short option.
 --token-table                         -k
 --verbose                             -v
 --version                             -V
+--yacc                                -y
 @end example
 @end ifinfo
 
@@ -5249,6 +5776,22 @@ would instead be named @file{foo_tab.c}.
 @cindex symbols in Bison, table of
 
 @table @code
+@item @@$
+In an action, the location of the left-hand side of the rule.
+  @xref{Locations, , Locations Overview}.
+
+@item @@@var{n}
+In an action, the location of the @var{n}-th symbol of the right-hand
+side of the rule.  @xref{Locations, , Locations Overview}.
+
+@item $$
+In an action, the semantic value of the left-hand side of the rule.
+@xref{Actions}.
+
+@item $@var{n}
+In an action, the semantic value of the @var{n}-th symbol of the
+right-hand side of the rule.  @xref{Actions}.
+
 @item error
 A token name reserved for error recovery.  This token may be used in
 grammar rules so as to allow the Bison parser to recognize an error in
@@ -5274,6 +5817,10 @@ read, by making @code{yyparse} return 0 immediately.
 Macro to discard a value from the parser stack and fake a look-ahead
 token.  @xref{Action Features, ,Special Features for Use in Actions}.
 
+@item YYDEBUG
+Macro to define to equip the parser with tracing code. @xref{Tracing,
+,Tracing Your Parser}.
+
 @item YYERROR
 Macro to pretend that a syntax error has just been detected: call
 @code{yyerror} and then perform normal error recovery if possible
@@ -5336,7 +5883,7 @@ look-ahead token.  @xref{Error Recovery}.
 @item yydebug
 External integer variable set to zero by default.  If @code{yydebug}
 is given a nonzero value, the parser will output information on input
-symbols and parser action.  @xref{Debugging, ,Debugging Your Parser}.
+symbols and parser action.  @xref{Tracing, ,Tracing Your Parser}.
 
 @item yyerrok
 Macro to cause parser to recover immediately to its normal mode
@@ -5349,8 +5896,9 @@ containing an error message.  @xref{Error Reporting, ,The Error
 Reporting Function @code{yyerror}}.
 
 @item yylex
-User-supplied lexical analyzer function, called with no arguments
-to get the next token.  @xref{Lexical, ,The Lexical Analyzer Function @code{yylex}}.
+User-supplied lexical analyzer function, called with no arguments to get
+the next token.  @xref{Lexical, ,The Lexical Analyzer Function
+@code{yylex}}.
 
 @item yylval
 External variable in which @code{yylex} should place the semantic
@@ -5386,11 +5934,11 @@ Bison declaration to create a header file meant for the scanner.
 Bison declaration to set tge prefix of the output files. @xref{Decl
 Summary}.
 
-@c @item %source_extension
+@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 @item %header-extension
 @c Bison declaration to specify the generated parser header file extension
 @c if required. @xref{Decl Summary}.
 
@@ -5426,7 +5974,8 @@ Bison declaration to assign right associativity to token(s).
 @xref{Precedence Decl, ,Operator Precedence}.
 
 @item %start
-Bison declaration to specify the start symbol.  @xref{Start Decl, ,The Start-Symbol}.
+Bison declaration to specify the start symbol.  @xref{Start Decl, ,The
+Start-Symbol}.
 
 @item %token
 Bison declaration to declare token(s) without specifying precedence.
@@ -5437,13 +5986,16 @@ Bison declaration to include a token name table in the parser file.
 @xref{Decl Summary}.
 
 @item %type
-Bison declaration to declare nonterminals.  @xref{Type Decl, ,Nonterminal Symbols}.
+Bison declaration to declare nonterminals.  @xref{Type Decl,
+,Nonterminal Symbols}.
 
 @item %union
 Bison declaration to specify several possible data types for semantic
 values.  @xref{Union Decl, ,The Collection of Value Types}.
 @end table
 
+@sp 1
+
 These are the punctuation and delimiters used in Bison input:
 
 @table @samp