* doc/bison.texinfo: Formatting changes.

[bison.git] / doc / bison.texinfo

diff --git a/doc/bison.texinfo b/doc/bison.texinfo
index c4f19339860b83ba8da67068d3dcdf679c4b2299..ff86f539d0eb4df6ddaac14f258d9a4290dbfbae 100644 (file)
--- a/doc/bison.texinfo
+++ b/doc/bison.texinfo
@@ -447,16 +447,26 @@ lexicography, not grammar.)
 
 Here is a simple C function subdivided into tokens:
 
 
 Here is a simple C function subdivided into tokens:
 

+@ifinfo

 @example
 int             /* @r{keyword `int'} */
 @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,}
+                   @r{identifier, close-paren} */

 @{               /* @r{open-brace} */
 @{               /* @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
 @}               /* @r{close-brace} */
 @end example

+@end ifinfo
+@ifnotinfo
+@example
+int             /* @r{keyword `int'} */
+square (int x)  /* @r{identifier, open-paren, identifier, identifier, close-paren} */
+@{               /* @r{open-brace} */
+  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
 
 The syntactic groupings of C include the expression, the statement, the
 declaration, and the function definition.  These are represented in the


@@ -666,12 +676,13 @@ 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.
 
 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
 
 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 +694,7 @@ 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
 @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.
 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 +703,15 @@ 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.
 
 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.  In the same situation,
+C++ parsers may include @code{<cstddef>} and @code{<cstdlib>} instead.
+Other system headers may be included if you define @code{YYDEBUG} to a
+nonzero value (@pxref{Debugging, ,Debugging Your Parser}).
+

 @node Stages
 @section Stages in Using Bison
 @cindex stages in using Bison
 @node Stages
 @section Stages in Using Bison
 @cindex stages in using Bison


@@ -703,15 +723,16 @@ to a working compiler or interpreter, has these parts:
 @enumerate
 @item
 Formally specify the grammar in a form recognized by Bison
 @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
 
 @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.
 
 @item
 Write a controlling function that calls the Bison-produced parser.


@@ -865,9 +886,10 @@ which is a floating point number.
 The @code{#include} directive is used to declare the exponentiation
 function @code{pow}.
 
 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
 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 +1069,10 @@ The latter, however, is much more readable.
 @cindex writing a lexical analyzer
 @cindex lexical analyzer, writing
 
 @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
 
 Only a simple lexical analyzer is needed for the RPN calculator.  This
 lexical analyzer skips blanks and tabs, then reads in numbers as


@@ -1204,19 +1227,19 @@ Here is how to compile and run the parser file:
 @example
 @group
 # @r{List files in current directory.}
 @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}.}
 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.}
 @end group
 
 @group
 # @r{List files again.}

-% ls
+$ @kbd{ls}

 rpcalc  rpcalc.tab.c  rpcalc.y
 @end group
 @end example
 rpcalc  rpcalc.tab.c  rpcalc.y
 @end group
 @end example


@@ -1225,19 +1248,19 @@ The file @file{rpcalc} now contains the executable code.  Here is an
 example session using @code{rpcalc}.
 
 @example
 example session using @code{rpcalc}.
 
 @example

-% rpcalc
-4 9 +
+$ @kbd{rpcalc}
+@kbd{4 9 +}

 13
 13

-3 7 + 3 4 5 *+-
+@kbd{3 7 + 3 4 5 *+-}

 -13
 -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
 13

-5 6 / 4 n +
+@kbd{5 6 / 4 n +}

 -3.166666667
 -3.166666667

-3 4 ^                            @r{Exponentiation}
+@kbd{3 4 ^}                            @r{Exponentiation}

 81
 81

-^D                               @r{End-of-file indicator}
-%
+@kbd{^D}                               @r{End-of-file indicator}
+$

 @end example
 
 @node Infix Calc
 @end example
 
 @node Infix Calc


@@ -1306,23 +1329,25 @@ 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
 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
 
 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
 6.880952381

--56 + 2
+@kbd{-56 + 2}

 -54
 -54

-3 ^ 2
+@kbd{3 ^ 2}

 9
 @end example
 
 9
 @end example
 


@@ -1374,13 +1399,11 @@ Bison programs.
 @cindex @code{ltcalc}
 @cindex calculator, location tracking
 
 @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.
 
 @menu
 * Decls: Ltcalc Decls.  Bison and C declarations for ltcalc.


@@ -1391,8 +1414,8 @@ in the lexical analyser.
 @node Ltcalc Decls
 @subsection Declarations for @code{ltcalc}
 
 @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.  */
 
 @example
 /* Location tracking calculator.  */


@@ -1413,22 +1436,24 @@ as the declarations for the infix notation calculator.
 %% /* Grammar follows */
 @end example
 
 %% /* 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}
 
 
 @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
 
 @example
 @group


@@ -1449,17 +1474,17 @@ exp     : NUM           @{ $$ = $1; @}
         | exp '-' exp   @{ $$ = $1 - $3; @}
         | exp '*' exp   @{ $$ = $1 * $3; @}
 @end group
         | exp '-' exp   @{ $$ = $1 - $3; @}
         | exp '*' exp   @{ $$ = $1 * $3; @}
 @end group

-        | exp '/' exp

 @group
 @group

+        | exp '/' exp

             @{
               if ($3)
                 $$ = $1 / $3;
               else
                 @{
                   $$ = 1;
             @{
               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
                 @}
             @}
 @end group


@@ -1474,25 +1499,24 @@ 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.
 
 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.
 
 
 @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
 
 @example
 @group


@@ -1542,17 +1566,18 @@ yylex (void)
 @}
 @end example
 
 @}
 @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
 
 @example

+@group

 int
 main (void)
 @{
 int
 main (void)
 @{


@@ -1560,11 +1585,12 @@ main (void)
   yylloc.first_column = yylloc.last_column = 0;
   return yyparse ();
 @}
   yylloc.first_column = yylloc.last_column = 0;
   return yyparse ();
 @}

+@end group

 @end example
 
 @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}
 
 @node Multi-function Calc
 @section Multi-Function Calculator: @code{mfcalc}


@@ -1594,20 +1620,20 @@ to create named variables, store values in them, and use them later.
 Here is a sample session with the multi-function calculator:
 
 @example
 Here is a sample session with the multi-function calculator:
 
 @example

-% mfcalc
-pi = 3.141592653589
+$ @kbd{mfcalc}
+@kbd{pi = 3.141592653589}

 3.1415926536
 3.1415926536

-sin(pi)
+@kbd{sin(pi)}

 0.0000000000
 0.0000000000

-alpha = beta1 = 2.3
+@kbd{alpha = beta1 = 2.3}

 2.3000000000
 2.3000000000

-alpha
+@kbd{alpha}

 2.3000000000
 2.3000000000

-ln(alpha)
+@kbd{ln(alpha)}

 0.8329091229
 0.8329091229

-exp(ln(beta1))
+@kbd{exp(ln(beta1))}

 2.3000000000
 2.3000000000

-%
+$

 @end example
 
 Note that multiple assignment and nested function calls are permitted.
 @end example
 
 Note that multiple assignment and nested function calls are permitted.


@@ -1663,11 +1689,12 @@ are @code{NUM}, @code{VAR}, @code{FNCT}, and @code{exp}.  Their
 declarations are augmented with information about their data type (placed
 between angle brackets).
 
 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}
 
 @node Mfcalc Rules
 @subsection Grammar Rules for @code{mfcalc}


@@ -1941,8 +1968,8 @@ yylex (void)
 @end smallexample
 
 This program is both powerful and flexible. You may easily add new
 @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
 
 @node Exercises
 @section Exercises


@@ -2405,7 +2432,8 @@ requires you to do two things:
 @itemize @bullet
 @item
 Specify the entire collection of possible data types, with the
 @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
 
 @item
 Choose one of those types for each symbol (terminal or nonterminal) for


@@ -2427,10 +2455,11 @@ 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
 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
 
 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


@@ -2710,8 +2739,8 @@ especially symbol locations.
 
 @c (terminal or not) ?
 
 
 @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.
 
 @menu
 * Location Type::               Specifying a data type for locations.


@@ -2812,11 +2841,11 @@ exp:    @dots{}
 @subsection Default Action for Locations
 @vindex YYLLOC_DEFAULT
 
 @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.
 
 Most of the time, this macro is general enough to suppress location
 dedicated code from semantic actions.


@@ -2868,7 +2897,8 @@ 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
 
 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.
 
 @menu
 * Token Decl::        Declaring terminal symbols.


@@ -2917,7 +2947,8 @@ 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:
 


@@ -2964,7 +2995,8 @@ 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}.
 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
 
 The syntax of a precedence declaration is the same as that of
 @code{%token}: either


@@ -3051,11 +3083,12 @@ used.  This is done with a @code{%type} declaration, like this:
 @end example
 
 @noindent
 @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
 
 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


@@ -3071,11 +3104,11 @@ terminal symbol.  All kinds of token declarations allow
 @findex %expect
 
 Bison normally warns if there are any conflicts in the grammar
 @findex %expect
 
 Bison normally warns if there are any conflicts in the grammar

-(@pxref{Shift/Reduce, ,Shift/Reduce Conflicts}), but most real grammars have harmless shift/reduce
-conflicts which are resolved in a predictable way and would be difficult to
-eliminate.  It is desirable to suppress the warning about these conflicts
-unless the number of conflicts changes.  You can do this with the
-@code{%expect} declaration.
+(@pxref{Shift/Reduce, ,Shift/Reduce Conflicts}), but most real grammars
+have harmless shift/reduce conflicts which are resolved in a predictable
+way and would be difficult to eliminate.  It is desirable to suppress
+the warning about these conflicts unless the number of conflicts
+changes.  You can do this with the @code{%expect} declaration.

 
 The declaration looks like this:
 
 
 The declaration looks like this:
 


@@ -3083,10 +3116,11 @@ The declaration looks like this:
 %expect @var{n}
 @end example
 
 %expect @var{n}
 @end example
 

-Here @var{n} is a decimal integer.  The declaration says there should be no
-warning if there are @var{n} shift/reduce conflicts and no reduce/reduce
-conflicts.  The usual warning is given if there are either more or fewer
-conflicts, or if there are any reduce/reduce conflicts.
+Here @var{n} is a decimal integer.  The declaration says there should be
+no warning if there are @var{n} shift/reduce conflicts and no
+reduce/reduce conflicts.  An error, instead of the usual warning, is
+given if there are either more or fewer conflicts, or if there are any
+reduce/reduce conflicts.

 
 In general, using @code{%expect} involves these steps:
 
 
 In general, using @code{%expect} involves these steps:
 


@@ -3215,9 +3249,9 @@ directives:
 
 @table @code
 @item %debug
 
 @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{Debugging, ,Debugging Your Parser}.

 
 @item %defines
 Write an extra output file containing macro definitions for the token
 
 @item %defines
 Write an extra output file containing macro definitions for the token


@@ -3357,10 +3391,10 @@ 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}}
 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
 
 The precise list of symbols renamed is @code{yyparse}, @code{yylex},
 @code{yyerror}, @code{yynerrs}, @code{yylval}, @code{yychar} and


@@ -3554,9 +3588,10 @@ 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
 @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
 
 @example
 @group


@@ -3765,8 +3800,8 @@ 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
 @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
 
 @node Action Features
 @section Special Features for Use in Actions


@@ -3787,7 +3822,8 @@ Acts like a variable that contains the semantic value for the
 
 @item $<@var{typealt}>$
 Like @code{$$} but specifies alternative @var{typealt} in the union
 
 @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
 
 @item $<@var{typealt}>@var{n}
 Like @code{$@var{n}} but specifies alternative @var{typealt} in the


@@ -4216,18 +4252,19 @@ 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
 
 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.
 
 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.


@@ -4904,14 +4941,23 @@ 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
 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.
-
-The trace facility uses @code{stderr}, so you must add
-@w{@code{#include <stdio.h>}} to the prologue unless it is already there.
+@code{YYDEBUG} to a nonzero value 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}) or the
+@code{%debug} declaration (@pxref{Decl Summary, ,Bison Declaration
+Summary}).  We suggest that you always define @code{YYDEBUG} so that
+debugging is always possible.
+
+The trace facility outputs messages with macro calls of the form
+@code{YYFPRINTF (YYSTDERR, @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 the macros are defined to @code{fprintf} and @code{stderr}.  In
+the same situation, C++ parsers include @code{<cstdio.h>} instead, and
+use @code{std::fprintf} and @code{std::stderr}.

 
 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}.
 
 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}.


@@ -4936,13 +4982,14 @@ of the state stack afterward.
 @end itemize
 
 To make sense of this information, it helps to refer to the listing file
 @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
 
 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


@@ -4990,7 +5037,7 @@ 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
 @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++}).
 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++}).


@@ -5072,9 +5119,9 @@ you are developing Bison.
 
 @item -t
 @itemx --debug
 
 @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{Debugging, ,Debugging Your Parser}.

 
 @item --locations
 Pretend that @code{%locations} was specified.  @xref{Decl Summary}.
 
 @item --locations
 Pretend that @code{%locations} was specified.  @xref{Decl Summary}.


@@ -5348,8 +5395,9 @@ containing an error message.  @xref{Error Reporting, ,The Error
 Reporting Function @code{yyerror}}.
 
 @item yylex
 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
 
 @item yylval
 External variable in which @code{yylex} should place the semantic


@@ -5425,7 +5473,8 @@ Bison declaration to assign right associativity to token(s).
 @xref{Precedence Decl, ,Operator Precedence}.
 
 @item %start
 @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.
 
 @item %token
 Bison declaration to declare token(s) without specifying precedence.


@@ -5436,7 +5485,8 @@ Bison declaration to include a token name table in the parser file.
 @xref{Decl Summary}.
 
 @item %type
 @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
 
 @item %union
 Bison declaration to specify several possible data types for semantic