@contents
-@node Top, Introduction, (dir), (dir)
+@ifnottex
+@node Top
+@top Bison
-@ifinfo
-This manual documents version @value{VERSION} of Bison.
-@end ifinfo
+This manual documents version @value{VERSION} of Bison, updated
+@value{UPDATED}.
+@end ifnottex
@menu
* Introduction::
* Copying This Manual:: License for copying this manual.
* Index:: Cross-references to the text.
- --- The Detailed Node Listing ---
+@detailmenu --- The Detailed Node Listing ---
The Concepts of Bison
* Infix Calc:: Infix (algebraic) notation calculator.
Operator precedence is introduced.
* Simple Error Recovery:: Continuing after syntax errors.
+* Location Tracking Calc:: Demonstrating the use of @@@var{n} and @@$.
* Multi-function Calc:: Calculator with memory and trig functions.
It uses multiple data-types for semantic values.
* Exercises:: Ideas for improving the multi-function calculator.
Reverse Polish Notation Calculator
-* Decls: Rpcalc Decls. Bison and C declarations for rpcalc.
+* Decls: Rpcalc Decls. Prologue (declarations) for rpcalc.
* Rules: Rpcalc Rules. Grammar Rules for rpcalc, with explanation.
* Lexer: Rpcalc Lexer. The lexical analyzer.
* Main: Rpcalc Main. The controlling function.
* Rpcalc Line::
* Rpcalc Expr::
+Location Tracking Calculator: @code{ltcalc}
+
+* Decls: Ltcalc Decls. Bison and C declarations for ltcalc.
+* Rules: Ltcalc Rules. Grammar rules for ltcalc, with explanations.
+* Lexer: Ltcalc Lexer. The lexical analyzer.
+
Multi-Function Calculator: @code{mfcalc}
* Decl: Mfcalc Decl. Bison declarations for multi-function calculator.
Outline of a Bison Grammar
-* C Declarations:: Syntax and usage of the C declarations section.
+* Prologue:: Syntax and usage of the prologue (declarations section).
* Bison Declarations:: Syntax and usage of the Bison declarations section.
* Grammar Rules:: Syntax and usage of the grammar rules section.
-* C Code:: Syntax and usage of the additional C code section.
+* Epilogue:: Syntax and usage of the epilogue (additional code section).
Defining Language Semantics
* GNU Free Documentation License:: License for copying this manual.
+@end detailmenu
@end menu
-@node Introduction, Conditions, Top, Top
+@node Introduction
@unnumbered Introduction
@cindex introduction
This edition corresponds to version @value{VERSION} of Bison.
-@node Conditions, Copying, Introduction, Top
+@node Conditions
@unnumbered Conditions for Using Bison
As of Bison version 1.24, we have changed the distribution terms for
@include gpl.texi
-@node Concepts, Examples, Copying, Top
+@node Concepts
@chapter The Concepts of Bison
This chapter introduces many of the basic concepts without which the
* Grammar Layout:: Overall structure of a Bison grammar file.
@end menu
-@node Language and Grammar, Grammar in Bison, , Concepts
+@node Language and Grammar
@section Languages and Context-Free Grammars
@cindex context-free 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
must be a `sequence of definitions and declarations'. If not, the parser
reports a syntax error.
-@node Grammar in Bison, Semantic Values, Language and Grammar, Concepts
+@node Grammar in Bison
@section From Formal Rules to Bison Input
@cindex Bison grammar
@cindex grammar, Bison
@noindent
@xref{Rules, ,Syntax of Grammar Rules}.
-@node Semantic Values, Semantic Actions, Grammar in Bison, Concepts
+@node Semantic Values
@section Semantic Values
@cindex semantic value
@cindex value, semantic
language, an expression typically has a semantic value that is a tree
structure describing the meaning of the expression.
-@node Semantic Actions, Locations Overview, Semantic Values, Concepts
+@node Semantic Actions
@section Semantic Actions
@cindex semantic actions
@cindex actions, semantic
The action says how to produce the semantic value of the sum expression
from the values of the two subexpressions.
-@node Locations Overview, Bison Parser, Semantic Actions, Concepts
+@node Locations Overview
@section Locations
@cindex location
@cindex textual position
grouping, the default behavior of the output parser is to take the beginning
of the first symbol, and the end of the last symbol.
-@node Bison Parser, Stages, Locations Overview, Concepts
+@node Bison Parser
@section Bison Output: the Parser File
@cindex Bison parser
@cindex Bison utility
@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.
or @samp{YY} in the Bison grammar file except for the ones defined in
this manual.
-@node Stages, Grammar Layout, Bison Parser, Concepts
+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}
+(@pxref{Debugging, ,Debugging Your Parser}).
+
+@node Stages
@section Stages in Using Bison
@cindex stages in using Bison
@cindex using Bison
Link the object files to produce the finished product.
@end enumerate
-@node Grammar Layout, , Stages, Concepts
+@node Grammar Layout
@section The Overall Layout of a Bison Grammar
@cindex grammar file
@cindex file format
@example
%@{
-@var{C declarations}
+@var{Prologue (declarations)}
%@}
@var{Bison declarations}
%%
@var{Grammar rules}
%%
-@var{Additional C code}
+@var{Epilogue (additional code)}
@end example
@noindent
The @samp{%%}, @samp{%@{} and @samp{%@}} are punctuation that appears
in every Bison grammar file to separate the sections.
-The C declarations may define types and variables used in the actions.
-You can also use preprocessor commands to define macros used there, and use
+The prologue may define types and variables used in the actions. You can
+also use preprocessor commands to define macros used there, and use
@code{#include} to include header files that do any of these things.
The Bison declarations declare the names of the terminal and nonterminal
The grammar rules define how to construct each nonterminal symbol from its
parts.
-The additional C code can contain any C code you want to use. Often the
-definition of the lexical analyzer @code{yylex} goes here, plus subroutines
-called by the actions in the grammar rules. In a simple program, all the
-rest of the program can go here.
+The epilogue can contain any code you want to use. Often the definition of
+the lexical analyzer @code{yylex} goes here, plus subroutines called by the
+actions in the grammar rules. In a simple program, all the rest of the
+program can go here.
-@node Examples, Grammar File, Concepts, Top
+@node Examples
@chapter Examples
@cindex simple examples
@cindex examples, simple
* Infix Calc:: Infix (algebraic) notation calculator.
Operator precedence is introduced.
* Simple Error Recovery:: Continuing after syntax errors.
+* Location Tracking Calc:: Demonstrating the use of @@@var{n} and @@$.
* Multi-function Calc:: Calculator with memory and trig functions.
It uses multiple data-types for semantic values.
* Exercises:: Ideas for improving the multi-function calculator.
@end menu
-@node RPN Calc, Infix Calc, , Examples
+@node RPN Calc
@section Reverse Polish Notation Calculator
@cindex reverse polish notation
@cindex polish notation calculator
@samp{.y} extension is a convention used for Bison input files.
@menu
-* Decls: Rpcalc Decls. Bison and C declarations for rpcalc.
+* Decls: Rpcalc Decls. Prologue (declarations) for rpcalc.
* Rules: Rpcalc Rules. Grammar Rules for rpcalc, with explanation.
* Lexer: Rpcalc Lexer. The lexical analyzer.
* Main: Rpcalc Main. The controlling function.
* Comp: Rpcalc Compile. Run the C compiler on the output code.
@end menu
-@node Rpcalc Decls, Rpcalc Rules, , RPN Calc
+@node Rpcalc Decls
@subsection Declarations for @code{rpcalc}
Here are the C and Bison declarations for the reverse polish notation
%% /* Grammar rules and actions follow */
@end example
-The C declarations section (@pxref{C Declarations, ,The C Declarations Section}) contains two
+The declarations section (@pxref{Prologue, , The prologue}) contains two
preprocessor directives.
The @code{#define} directive defines the macro @code{YYSTYPE}, thus
-specifying the C data type for semantic values of both tokens and groupings
-(@pxref{Value Type, ,Data Types of Semantic Values}). The Bison parser will use whatever type
-@code{YYSTYPE} is defined as; if you don't define it, @code{int} is the
-default. Because we specify @code{double}, each token and each expression
-has an associated value, which is a floating point number.
+specifying the C data type for semantic values of both tokens and
+groupings (@pxref{Value Type, ,Data Types of Semantic Values}). The
+Bison parser will use whatever type @code{YYSTYPE} is defined as; if you
+don't define it, @code{int} is the default. Because we specify
+@code{double}, each token and each expression has an associated value,
+which is a floating point number.
The @code{#include} directive is used to declare the exponentiation
function @code{pow}.
only terminal symbol that needs to be declared is @code{NUM}, the token
type for numeric constants.
-@node Rpcalc Rules, Rpcalc Lexer, Rpcalc Decls, RPN Calc
+@node Rpcalc Rules
@subsection Grammar Rules for @code{rpcalc}
Here are the grammar rules for the reverse polish notation calculator.
* Rpcalc Expr::
@end menu
-@node Rpcalc Input, Rpcalc Line, , Rpcalc Rules
+@node Rpcalc Input
@subsubsection Explanation of @code{input}
Consider the definition of @code{input}:
grammatical error is seen or the lexical analyzer says there are no more
input tokens; we will arrange for the latter to happen at end of file.
-@node Rpcalc Line, Rpcalc Expr, Rpcalc Input, Rpcalc Rules
+@node Rpcalc Line
@subsubsection Explanation of @code{line}
Now consider the definition of @code{line}:
that value were ever used, but we don't use it: once rpcalc has printed the
value of the user's input line, that value is no longer needed.
-@node Rpcalc Expr, , Rpcalc Line, Rpcalc Rules
+@node Rpcalc Expr
@subsubsection Explanation of @code{expr}
The @code{exp} grouping has several rules, one for each kind of expression.
@noindent
The latter, however, is much more readable.
-@node Rpcalc Lexer, Rpcalc Main, Rpcalc Rules, RPN Calc
+@node Rpcalc Lexer
@subsection The @code{rpcalc} Lexical Analyzer
@cindex writing a lexical analyzer
@cindex lexical analyzer, writing
macro whose definition is the appropriate number. In this example,
therefore, @code{NUM} becomes a macro for @code{yylex} to use.
-The semantic value of the token (if it has one) is stored into the global
-variable @code{yylval}, which is where the Bison parser will look for it.
-(The C data type of @code{yylval} is @code{YYSTYPE}, which was defined
-at the beginning of the grammar; @pxref{Rpcalc Decls, ,Declarations for @code{rpcalc}}.)
+The semantic value of the token (if it has one) is stored into the
+global variable @code{yylval}, which is where the Bison parser will look
+for it. (The C data type of @code{yylval} is @code{YYSTYPE}, which was
+defined at the beginning of the grammar; @pxref{Rpcalc Decls,
+,Declarations for @code{rpcalc}}.)
A token type code of zero is returned if the end-of-file is encountered.
(Bison recognizes any nonpositive value as indicating the end of the
@end group
@end example
-@node Rpcalc Main, Rpcalc Error, Rpcalc Lexer, RPN Calc
+@node Rpcalc Main
@subsection The Controlling Function
@cindex controlling function
@cindex main function in simple example
@end group
@end example
-@node Rpcalc Error, Rpcalc Gen, Rpcalc Main, RPN Calc
+@node Rpcalc Error
@subsection The Error Reporting Routine
@cindex error reporting routine
cause the calculator program to exit. This is not clean behavior for a
real calculator, but it is adequate for the first example.
-@node Rpcalc Gen, Rpcalc Compile, Rpcalc Error, RPN Calc
+@node Rpcalc Gen
@subsection Running Bison to Make the Parser
@cindex running Bison (introduction)
arrange all the source code in one or more source files. For such a
simple example, the easiest thing is to put everything in one file. The
definitions of @code{yylex}, @code{yyerror} and @code{main} go at the
-end, in the ``additional C code'' section of the file (@pxref{Grammar
-Layout, ,The Overall Layout of a Bison Grammar}).
+end, in the epilogue of the file
+(@pxref{Grammar Layout, ,The Overall Layout of a Bison Grammar}).
For a large project, you would probably have several source files, and use
@code{make} to arrange to recompile them.
functions in the input file (@code{yylex}, @code{yyerror} and @code{main})
are copied verbatim to the output.
-@node Rpcalc Compile, , Rpcalc Gen, RPN Calc
+@node Rpcalc Compile
@subsection Compiling the Parser File
@cindex compiling the parser
@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
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, Simple Error Recovery, RPN Calc, Examples
+@node Infix Calc
@section Infix Notation Calculator: @code{calc}
@cindex infix notation calculator
@cindex @code{calc}
@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
-@node Simple Error Recovery, Multi-function Calc, Infix Calc, Examples
+@node Simple Error Recovery
@section Simple Error Recovery
@cindex error recovery, simple
input. We won't discuss this issue further because it is not specific to
Bison programs.
-@node Multi-function Calc, Exercises, Simple Error Recovery, Examples
+@node Location Tracking Calc
+@section Location Tracking Calculator: @code{ltcalc}
+@cindex location tracking calculator
+@cindex @code{ltcalc}
+@cindex calculator, location tracking
+
+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.
+* Rules: Ltcalc Rules. Grammar rules for ltcalc, with explanations.
+* Lexer: Ltcalc Lexer. The lexical analyzer.
+@end menu
+
+@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.
+
+@example
+/* Location tracking calculator. */
+
+%@{
+#define YYSTYPE int
+#include <math.h>
+%@}
+
+/* Bison declarations. */
+%token NUM
+
+%left '-' '+'
+%left '*' '/'
+%left NEG
+%right '^'
+
+%% /* Grammar follows */
+@end example
+
+@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 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.
+
+@example
+@group
+input : /* empty */
+ | input line
+;
+@end group
+
+@group
+line : '\n'
+ | exp '\n' @{ printf ("%d\n", $1); @}
+;
+@end group
+
+@group
+exp : NUM @{ $$ = $1; @}
+ | exp '+' exp @{ $$ = $1 + $3; @}
+ | exp '-' exp @{ $$ = $1 - $3; @}
+ | exp '*' exp @{ $$ = $1 * $3; @}
+@end group
+@group
+ | exp '/' exp
+ @{
+ if ($3)
+ $$ = $1 / $3;
+ else
+ @{
+ $$ = 1;
+ fprintf (stderr, "%d.%d-%d.%d: division by zero",
+ @@3.first_line, @@3.first_column,
+ @@3.last_line, @@3.last_column);
+ @}
+ @}
+@end group
+@group
+ | '-' exp %preg NEG @{ $$ = -$2; @}
+ | exp '^' exp @{ $$ = pow ($1, $3); @}
+ | '(' exp ')' @{ $$ = $2; @}
+@end group
+@end example
+
+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.
+
+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 the token locations, as it already does for
+semantic values.
+
+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
+int
+yylex (void)
+@{
+ int c;
+
+ /* skip white space */
+ while ((c = getchar ()) == ' ' || c == '\t')
+ ++yylloc.last_column;
+
+ /* step */
+ yylloc.first_line = yylloc.last_line;
+ yylloc.first_column = yylloc.last_column;
+@end group
+
+@group
+ /* process numbers */
+ if (isdigit (c))
+ @{
+ yylval = c - '0';
+ ++yylloc.last_column;
+ while (isdigit (c = getchar ()))
+ @{
+ ++yylloc.last_column;
+ yylval = yylval * 10 + c - '0';
+ @}
+ ungetc (c, stdin);
+ return NUM;
+ @}
+@end group
+
+ /* return end-of-file */
+ if (c == EOF)
+ return 0;
+
+ /* return single chars and update location */
+ if (c == '\n')
+ @{
+ ++yylloc.last_line;
+ yylloc.last_column = 0;
+ @}
+ else
+ ++yylloc.last_column;
+ return c;
+@}
+@end example
+
+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 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)
+@{
+ yylloc.first_line = yylloc.last_line = 1;
+ 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.
+
+@node Multi-function Calc
@section Multi-Function Calculator: @code{mfcalc}
@cindex multi-function calculator
@cindex @code{mfcalc}
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.
* Symtab: Mfcalc Symtab. Symbol table management subroutines.
@end menu
-@node Mfcalc Decl, Mfcalc Rules, , Multi-function Calc
+@node Mfcalc Decl
@subsection Declarations for @code{mfcalc}
Here are the C and Bison declarations for the multi-function calculator.
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, Mfcalc Symtab, Mfcalc Decl, Multi-function Calc
+@node Mfcalc Rules
@subsection Grammar Rules for @code{mfcalc}
Here are the grammar rules for the multi-function calculator.
%%
@end smallexample
-@node Mfcalc Symtab, , Mfcalc Rules, Multi-function Calc
+@node Mfcalc Symtab
@subsection The @code{mfcalc} Symbol Table
@cindex symbol table example
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, , Multi-function Calc, Examples
+@node Exercises
@section Exercises
@cindex exercises
uninitialized variable in any way except to store a value in it.
@end enumerate
-@node Grammar File, Interface, Examples, Top
+@node Grammar File
@chapter Bison Grammar Files
Bison takes as input a context-free grammar specification and produces a
* Multiple Parsers:: Putting more than one Bison parser in one program.
@end menu
-@node Grammar Outline, Symbols, , Grammar File
+@node Grammar Outline
@section Outline of a Bison Grammar
A Bison grammar file has four main sections, shown here with the
@example
%@{
-@var{C declarations}
+@var{Prologue}
%@}
@var{Bison declarations}
@var{Grammar rules}
%%
-@var{Additional C code}
+@var{Epilogue}
@end example
Comments enclosed in @samp{/* @dots{} */} may appear in any of the sections.
@menu
-* C Declarations:: Syntax and usage of the C declarations section.
+* Prologue:: Syntax and usage of the prologue.
* Bison Declarations:: Syntax and usage of the Bison declarations section.
* Grammar Rules:: Syntax and usage of the grammar rules section.
-* C Code:: Syntax and usage of the additional C code section.
+* Epilogue:: Syntax and usage of the epilogue.
@end menu
-@node C Declarations, Bison Declarations, , Grammar Outline
-@subsection The C Declarations Section
-@cindex C declarations section
-@cindex declarations, C
+@node Prologue, Bison Declarations, , Grammar Outline
+@subsection The prologue
+@cindex declarations section
+@cindex Prologue
+@cindex declarations
-The @var{C declarations} section contains macro definitions and
+The @var{prologue} section contains macro definitions and
declarations of functions and variables that are used in the actions in the
grammar rules. These are copied to the beginning of the parser file so
that they precede the definition of @code{yyparse}. You can use
need any C declarations, you may omit the @samp{%@{} and @samp{%@}}
delimiters that bracket this section.
-@node Bison Declarations, Grammar Rules, C Declarations, Grammar Outline
+@node Bison Declarations
@subsection The Bison Declarations Section
@cindex Bison declarations (introduction)
@cindex declarations, Bison (introduction)
In some simple grammars you may not need any declarations.
@xref{Declarations, ,Bison Declarations}.
-@node Grammar Rules, C Code, Bison Declarations, Grammar Outline
+@node Grammar Rules
@subsection The Grammar Rules Section
@cindex grammar rules section
@cindex rules section for grammar
@samp{%%} (which precedes the grammar rules) may never be omitted even
if it is the first thing in the file.
-@node C Code, , Grammar Rules, Grammar Outline
-@subsection The Additional C Code Section
+@node Epilogue, , Grammar Rules, Grammar Outline
+@subsection The epilogue
@cindex additional C code section
+@cindex epilogue
@cindex C code, section for additional
-The @var{additional C code} section is copied verbatim to the end of the
-parser file, just as the @var{C declarations} section is copied to the
-beginning. This is the most convenient place to put anything that you
-want to have in the parser file but which need not come before the
-definition of @code{yyparse}. For example, the definitions of
-@code{yylex} and @code{yyerror} often go here. @xref{Interface, ,Parser
-C-Language Interface}.
+The @var{epilogue} is copied verbatim to the end of the parser file, just as
+the @var{prologue} is copied to the beginning. This is the most convenient
+place to put anything that you want to have in the parser file but which need
+not come before the definition of @code{yyparse}. For example, the
+definitions of @code{yylex} and @code{yyerror} often go here.
+@xref{Interface, ,Parser C-Language Interface}.
If the last section is empty, you may omit the @samp{%%} that separates it
from the grammar rules.
The Bison parser itself contains many static variables whose names start
with @samp{yy} and many macros whose names start with @samp{YY}. It is a
good idea to avoid using any such names (except those documented in this
-manual) in the additional C code section of the grammar file.
+manual) in the epilogue of the grammar file.
-@node Symbols, Rules, Grammar Outline, Grammar File
+@node Symbols
@section Symbols, Terminal and Nonterminal
@cindex nonterminal symbol
@cindex terminal symbol
(@pxref{Error Recovery}); you shouldn't use it for any other purpose.
In particular, @code{yylex} should never return this value.
-@node Rules, Recursion, Symbols, Grammar File
+@node Rules
@section Syntax of Grammar Rules
@cindex rule syntax
@cindex grammar rule syntax
It is customary to write a comment @samp{/* empty */} in each rule
with no components.
-@node Recursion, Semantics, Rules, Grammar File
+@node Recursion
@section Recursive Rules
@cindex recursive rule
defines two mutually-recursive nonterminals, since each refers to the
other.
-@node Semantics, Locations, Recursion, Grammar File
+@node Semantics
@section Defining Language Semantics
@cindex defining language semantics
@cindex language semantics, defining
action in the middle of a rule.
@end menu
-@node Value Type, Multiple Types, , Semantics
+@node Value Type
@subsection Data Types of Semantic Values
@cindex semantic value type
@cindex value type, semantic
In a simple program it may be sufficient to use the same data type for
the semantic values of all language constructs. This was true in the
-RPN and infix calculator examples (@pxref{RPN Calc, ,Reverse Polish Notation Calculator}).
+RPN and infix calculator examples (@pxref{RPN Calc, ,Reverse Polish
+Notation Calculator}).
Bison's default is to use type @code{int} for all semantic values. To
specify some other type, define @code{YYSTYPE} as a macro, like this:
@end example
@noindent
-This macro definition must go in the C declarations section of the grammar
-file (@pxref{Grammar Outline, ,Outline of a Bison Grammar}).
+This macro definition must go in the prologue of the grammar file
+(@pxref{Grammar Outline, ,Outline of a Bison Grammar}).
-@node Multiple Types, Actions, Value Type, Semantics
+@node Multiple Types
@subsection More Than One Value Type
In most programs, you will need different data types for different kinds
Decl, ,Nonterminal Symbols}).
@end itemize
-@node Actions, Action Types, Multiple Types, Semantics
+@node Actions
@subsection Actions
@cindex action
@vindex $$
always refers to the @code{expr} which precedes @code{bar} in the
definition of @code{foo}.
-@node Action Types, Mid-Rule Actions, Actions, Semantics
+@node Action Types
@subsection Data Types of Values in Actions
@cindex action data types
@cindex data types in actions
then you can write @code{$<itype>1} to refer to the first subunit of the
rule as an integer, or @code{$<dtype>1} to refer to it as a double.
-@node Mid-Rule Actions, , Action Types, Semantics
+@node Mid-Rule Actions
@subsection Actions in Mid-Rule
@cindex actions in mid-rule
@cindex mid-rule actions
converted to an end-of-rule action in this way, and this is what Bison
actually does to implement mid-rule actions.
-@node Locations, Declarations, Semantics, Grammar File
+@node Locations
@section Tracking Locations
@cindex location
@cindex textual position
* Location Default Action:: Defining a general way to compute locations.
@end menu
-@node Location Type, Actions and Locations, , Locations
+@node Location Type
@subsection Data Type of Locations
@cindex data type of locations
@cindex default location type
@}
@end example
-@node Actions and Locations, Location Default Action, Location Type, Locations
+@node Actions and Locations
@subsection Actions and Locations
@cindex location actions
@cindex actions, location
@end group
@end example
-@node Location Default Action, , Actions and Locations, Locations
+@node Location Default Action
@subsection Default Action for Locations
@vindex YYLLOC_DEFAULT
range from 1 to @var{n}.
@end itemize
-@node Declarations, Multiple Parsers, Locations, Grammar File
+@node Declarations
@section Bison Declarations
@cindex declarations, Bison
@cindex Bison declarations
* Decl Summary:: Table of all Bison declarations.
@end menu
-@node Token Decl, Precedence Decl, , Declarations
+@node Token Decl
@subsection Token Type Names
@cindex declaring token type names
@cindex token type names, declaring
@code{yylex} function can use the token name or the literal string to
obtain the token type code number (@pxref{Calling Convention}).
-@node Precedence Decl, Union Decl, Token Decl, Declarations
+@node Precedence Decl
@subsection Operator Precedence
@cindex precedence declarations
@cindex declaring operator precedence
the one declared later has the higher precedence and is grouped first.
@end itemize
-@node Union Decl, Type Decl, Precedence Decl, Declarations
+@node Union Decl
@subsection The Collection of Value Types
@cindex declaring value types
@cindex value types, declaring
Note that, unlike making a @code{union} declaration in C, you do not write
a semicolon after the closing brace.
-@node Type Decl, Expect Decl, Union Decl, Declarations
+@node Type Decl
@subsection Nonterminal Symbols
@cindex declaring value types, nonterminals
@cindex value types, nonterminals, declaring
terminal symbol. All kinds of token declarations allow
@code{<@var{type}>}.
-@node Expect Decl, Start Decl, Type Decl, Declarations
+@node Expect Decl
@subsection Suppressing Conflict Warnings
@cindex suppressing conflict warnings
@cindex preventing warnings about conflicts
@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:
%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:
it will warn you again if changes in the grammar result in additional
conflicts.
-@node Start Decl, Pure Decl, Expect Decl, Declarations
+@node Start Decl
@subsection The Start-Symbol
@cindex declaring the start symbol
@cindex start symbol, declaring
%start @var{symbol}
@end example
-@node Pure Decl, Decl Summary, Start Decl, Declarations
+@node Pure Decl
@subsection A Pure (Reentrant) Parser
@cindex reentrant parser
@cindex pure parser
You can generate either a pure parser or a nonreentrant parser from any
valid grammar.
-@node Decl Summary, , Pure Decl, Declarations
+@node Decl Summary
@subsection Bison Declaration Summary
@cindex Bison declaration summary
@cindex declaration summary
@cindex summary, Bison declaration
-Here is a summary of all Bison declarations:
+Here is a summary of the declarations used to define a grammar:
@table @code
@item %union
@item %expect
Declare the expected number of shift-reduce conflicts
(@pxref{Expect Decl, ,Suppressing Conflict Warnings}).
+@end table
-@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.
+@sp 1
+@noindent
+In order to change the behavior of @command{bison}, use the following
+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}.
+
+@item %defines
+Write an extra output file containing macro definitions for the token
+type names defined in the grammar and the semantic value type
+@code{YYSTYPE}, as well as a few @code{extern} variable declarations.
+
+If the parser output file is named @file{@var{name}.c} then this file
+is named @file{@var{name}.h}.@refill
+
+This output file is essential if you wish to put the definition of
+@code{yylex} in a separate source file, because @code{yylex} needs to
+be able to refer to token type codes and the variable
+@code{yylval}. @xref{Token Values, ,Semantic Values of Tokens}.@refill
+
+@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 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 named @file{foo.tab.hh}
@item %locations
Generate the code processing the locations (@pxref{Action Features,
grammar does not use it, using @samp{%locations} allows for more
accurate parse error messages.
-@item %pure_parser
-Request a pure (reentrant) parser program (@pxref{Pure Decl, ,A Pure
-(Reentrant) Parser}).
+@item %name-prefix="@var{prefix}"
+Rename the external symbols used in the parser so that they start with
+@var{prefix} instead of @samp{yy}. The precise list of symbols renamed
+is @code{yyparse}, @code{yylex}, @code{yyerror}, @code{yynerrs},
+@code{yylval}, @code{yychar} and @code{yydebug}. For example, if you
+use @samp{%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
+@item %no-parser
Do not include any C code in the parser file; generate tables only. The
parser file contains just @code{#define} directives and static variable
declarations.
into a file named @file{@var{filename}.act}, in the form of a
brace-surrounded body fit for a @code{switch} statement.
-@item %no_lines
+@item %no-lines
Don't generate any @code{#line} preprocessor commands in the parser
file. Ordinarily Bison writes these commands in the parser file so that
the C compiler and debuggers will associate errors and object code with
associate errors with the parser file, treating it an independent source
file in its own right.
-@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}.
-
-@item %defines
-Write an extra output file containing macro definitions for the token
-type names defined in the grammar and the semantic value type
-@code{YYSTYPE}, as well as a few @code{extern} variable declarations.
-
-If the parser output file is named @file{@var{name}.c} then this file
-is named @file{@var{name}.h}.@refill
-
-This output file is essential if you wish to put the definition of
-@code{yylex} in a separate source file, because @code{yylex} needs to
-be able to refer to token type codes and the variable
-@code{yylval}. @xref{Token Values, ,Semantic Values of Tokens}.@refill
-
-@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.
-
-This file also describes all the conflicts, both those resolved by
-operator precedence and the unresolved ones.
+@item %output="@var{filename}"
+Specify the @var{filename} for the parser file.
-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
+@item %pure-parser
+Request a pure (reentrant) parser program (@pxref{Pure Decl, ,A Pure
+(Reentrant) Parser}).
-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
+@c @item %source_extension
+@c Specify the extension of the parser output file.
+@c
+@c For example, a grammar file named @file{foo.yy} and containing a
+@c @code{%source_extension .cpp} directive will produce a parser file
+@c named @file{foo.tab.cpp}
@item %token_table
Generate an array of token names in the parser file. The name of the
@item YYNSTATES
The number of parser states (@pxref{Parser States}).
@end table
+
+@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.
+
+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
-@node Multiple Parsers,, Declarations, Grammar File
+
+
+
+@node Multiple Parsers
@section Multiple Parsers in the Same Program
Most programs that use Bison parse only one language and therefore contain
@code{@var{prefix}parse}, and so on. This effectively substitutes one
name for the other in the entire parser file.
-@node Interface, Algorithm, Grammar File, Top
+@node Interface
@chapter Parser C-Language Interface
@cindex C-language interface
@cindex interface
Keep in mind that the parser uses many C identifiers starting with
@samp{yy} and @samp{YY} for internal purposes. If you use such an
-identifier (aside from those in this manual) in an action or in additional
-C code in the grammar file, you are likely to run into trouble.
+identifier (aside from those in this manual) in an action or in epilogue
+in the grammar file, you are likely to run into trouble.
@menu
* Parser Function:: How to call @code{yyparse} and what it returns.
* Action Features:: Special features for use in actions.
@end menu
-@node Parser Function, Lexical, , Interface
+@node Parser Function
@section The Parser Function @code{yyparse}
@findex yyparse
Return immediately with value 1 (to report failure).
@end table
-@node Lexical, Error Reporting, Parser Function, Interface
+@node Lexical
@section The Lexical Analyzer Function @code{yylex}
@findex yylex
@cindex lexical analyzer
in a pure parser (@pxref{Pure Decl, ,A Pure (Reentrant) Parser}).
@end menu
-@node Calling Convention, Token Values, , Lexical
+@node Calling Convention
@subsection Calling Convention for @code{yylex}
The value that @code{yylex} returns must be the numeric code for the type
@code{%token_table} declaration. @xref{Decl Summary}.
@end itemize
-@node Token Values, Token Positions, Calling Convention, Lexical
+@node Token Values
@subsection Semantic Values of Tokens
@vindex yylval
@end group
@end example
-@node Token Positions, Pure Calling, Token Values, Lexical
+@node Token Positions
@subsection Textual Positions of Tokens
@vindex yylloc
@tindex YYLTYPE
The data type of @code{yylloc} has the name @code{YYLTYPE}.
-@node Pure Calling, , Token Positions, Lexical
+@node Pure Calling
@subsection Calling Conventions for Pure Parsers
When you use the Bison declaration @code{%pure_parser} to request a
also using @code{YYPARSE_PARAM}. Then you should call @code{yyparse}
with no arguments, as usual.
-@node Error Reporting, Action Features, Lexical, Interface
+@node Error Reporting
@section The Error Reporting Function @code{yyerror}
@cindex error reporting function
@findex yyerror
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, , Error Reporting, Interface
+@node Action Features
@section Special Features for Use in Actions
@cindex summary, action features
@cindex action features summary
@end table
-@node Algorithm, Error Recovery, Interface, Top
+@node Algorithm
@chapter The Bison Parser Algorithm
@cindex Bison parser algorithm
@cindex algorithm of parser
* Stack Overflow:: What happens when stack gets full. How to avoid it.
@end menu
-@node Look-Ahead, Shift/Reduce, , Algorithm
+@node Look-Ahead
@section Look-Ahead Tokens
@cindex look-ahead token
The current look-ahead token is stored in the variable @code{yychar}.
@xref{Action Features, ,Special Features for Use in Actions}.
-@node Shift/Reduce, Precedence, Look-Ahead, Algorithm
+@node Shift/Reduce
@section Shift/Reduce Conflicts
@cindex conflicts
@cindex shift/reduce conflicts
;
@end example
-@node Precedence, Contextual Precedence, Shift/Reduce, Algorithm
+@node Precedence
@section Operator Precedence
@cindex operator precedence
@cindex precedence of operators
* How Precedence:: How they work.
@end menu
-@node Why Precedence, Using Precedence, , Precedence
+@node Why Precedence
@subsection When Precedence is Needed
Consider the following ambiguous grammar fragment (ambiguous because the
contains @w{@samp{1 - 2}} and the look-ahead token is @samp{-}: shifting
makes right-associativity.
-@node Using Precedence, Precedence Examples, Why Precedence, Precedence
+@node Using Precedence
@subsection Specifying Operator Precedence
@findex %left
@findex %right
precedence is lowest, the next such declaration declares the operators
whose precedence is a little higher, and so on.
-@node Precedence Examples, How Precedence, Using Precedence, Precedence
+@node Precedence Examples
@subsection Precedence Examples
In our example, we would want the following declarations:
and so on. We assume that these tokens are more than one character long
and therefore are represented by names, not character literals.)
-@node How Precedence, , Precedence Examples, Precedence
+@node How Precedence
@subsection How Precedence Works
The first effect of the precedence declarations is to assign precedence
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.
-@node Contextual Precedence, Parser States, Precedence, Algorithm
+@node Contextual Precedence
@section Context-Dependent Precedence
@cindex context-dependent precedence
@cindex unary operator precedence
@end group
@end example
-@node Parser States, Reduce/Reduce, Contextual Precedence, Algorithm
+@node Parser States
@section Parser States
@cindex finite-state machine
@cindex parser state
is erroneous in the current state. This causes error processing to begin
(@pxref{Error Recovery}).
-@node Reduce/Reduce, Mystery Conflicts, Parser States, Algorithm
+@node Reduce/Reduce
@section Reduce/Reduce Conflicts
@cindex reduce/reduce conflict
@cindex conflicts, reduce/reduce
;
@end example
-@node Mystery Conflicts, Stack Overflow, Reduce/Reduce, Algorithm
+@node Mystery Conflicts
@section Mysterious Reduce/Reduce Conflicts
Sometimes reduce/reduce conflicts can occur that don't look warranted.
;
@end example
-@node Stack Overflow, , Mystery Conflicts, Algorithm
+@node Stack Overflow
@section Stack Overflow, and How to Avoid It
@cindex stack overflow
@cindex parser stack overflow
macro @code{YYINITDEPTH}. This value too must be a compile-time
constant integer. The default is 200.
-@node Error Recovery, Context Dependency, Algorithm, Top
+@node Error Recovery
@chapter Error Recovery
@cindex error recovery
@cindex recovery from errors
rest of the time. A value of 1 indicates that error messages are
currently suppressed for new syntax errors.
-@node Context Dependency, Debugging, Error Recovery, Top
+@node Context Dependency
@chapter Handling Context Dependencies
The Bison paradigm is to parse tokens first, then group them into larger
(Actually, ``kludge'' means any technique that gets its job done but is
neither clean nor robust.)
-@node Semantic Tokens, Lexical Tie-ins, , Context Dependency
+@node Semantic Tokens
@section Semantic Info in Token Types
The C language has a context dependency: the way an identifier is used
program. A true lexical tie-in has a special-purpose flag controlled by
the syntactic context.
-@node Lexical Tie-ins, Tie-in Recovery, Semantic Tokens, Context Dependency
+@node Lexical Tie-ins
@section Lexical Tie-ins
@cindex lexical tie-in
it is nonzero, all integers are parsed in hexadecimal, and tokens starting
with letters are parsed as integers if possible.
-The declaration of @code{hexflag} shown in the C declarations section of
-the parser file is needed to make it accessible to the actions
-(@pxref{C Declarations, ,The C Declarations Section}). You must also write the code in @code{yylex}
-to obey the flag.
+The declaration of @code{hexflag} shown in the prologue of the parser file
+is needed to make it accessible to the actions (@pxref{Prologue, ,The Prologue}).
+You must also write the code in @code{yylex} to obey the flag.
-@node Tie-in Recovery, , Lexical Tie-ins, Context Dependency
+@node Tie-in Recovery
@section Lexical Tie-ins and Error Recovery
Lexical tie-ins make strict demands on any error recovery rules you have.
be such that you can be sure that it always will, or always won't, have to
clear the flag.
-@node Debugging, Invocation, Context Dependency, Top
+@node Debugging
@chapter Debugging Your Parser
@findex YYDEBUG
@findex yydebug
runs, the @code{yydebug} parser-trace feature can help you figure out why.
To enable compilation of trace facilities, you must define the macro
-@code{YYDEBUG} when you compile the parser. You could use
-@samp{-DYYDEBUG=1} as a compiler option or you could put @samp{#define
-YYDEBUG 1} in the C declarations section of the grammar file
-(@pxref{C Declarations, ,The C Declarations Section}). Alternatively, use the @samp{-t} option when
-you run Bison (@pxref{Invocation, ,Invoking Bison}). We always define @code{YYDEBUG} so that
-debugging is always possible.
-
-The trace facility uses @code{stderr}, so you must add @w{@code{#include
-<stdio.h>}} to the C declarations section unless it is already there.
+@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 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} 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}.
@}
@end smallexample
-@node Invocation, Table of Symbols, Debugging, Top
+@node Invocation
@chapter Invoking Bison
@cindex invoking Bison
@cindex Bison invocation
@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++}).
* VMS Invocation:: Bison command syntax on VMS.
@end menu
-@node Bison Options, Environment Variables, , Invocation
+@node Bison Options
@section Bison Options
Bison supports both traditional single-letter options and mnemonic long
Your Parser}.
@item --locations
-Pretend that @code{%locactions} was specified. @xref{Decl Summary}.
+Pretend that @code{%locations} was specified. @xref{Decl Summary}.
@item -p @var{prefix}
@itemx --name-prefix=@var{prefix}
-Rename the external symbols used in the parser so that they start with
-@var{prefix} instead of @samp{yy}. The precise list of symbols renamed
-is @code{yyparse}, @code{yylex}, @code{yyerror}, @code{yynerrs},
-@code{yylval}, @code{yychar} and @code{yydebug}.
-
-For example, if you use @samp{-p c}, the names become @code{cparse},
-@code{clex}, and so on.
-
-@xref{Multiple Parsers, ,Multiple Parsers in the Same Program}.
+Pretend that @code{%name-prefix="@var{prefix}"} was specified.
+@xref{Decl Summary}.
@item -l
@itemx --no-lines
@item -n
@itemx --no-parser
-Pretend that @code{%no_parser} was specified. @xref{Decl Summary}.
+Pretend that @code{%no-parser} was specified. @xref{Decl Summary}.
@item -k
@itemx --token-table
-Pretend that @code{%token_table} was specified. @xref{Decl Summary}.
+Pretend that @code{%token-table} was specified. @xref{Decl Summary}.
@end table
@noindent
@table @option
@item -d
@itemx --defines
-Pretend that @code{%verbose} was specified, i.e., write an extra output
+Pretend that @code{%defines} was specified, i.e., write an extra output
file containing macro definitions for the token type names defined in
the grammar and the semantic value type @code{YYSTYPE}, as well as a few
@code{extern} variable declarations. @xref{Decl Summary}.
+@item --defines=@var{defines-file}
+Same as above, but save in the file @var{defines-file}.
+
@item -b @var{file-prefix}
@itemx --file-prefix=@var{prefix}
-Specify a prefix to use for all Bison output file names. The names are
-chosen as if the input file were named @file{@var{prefix}.c}.
+Pretend that @code{%verbose} was specified, i.e, specify prefix to use
+for all Bison output file names. @xref{Decl Summary}.
@item -v
@itemx --verbose
Pretend that @code{%verbose} was specified, i.e, write an extra output
file containing verbose descriptions of the grammar and
-parser. @xref{Decl Summary}, for more.
+parser. @xref{Decl Summary}.
+
+@item -o @var{filename}
+@itemx --output=@var{filename}
+Specify the @var{filename} for the parser file.
-@item -o @var{outfile}
-@itemx --output-file=@var{outfile}
-Specify the name @var{outfile} for the parser file.
+The other output files' names are constructed from @var{filename} as
+described under the @samp{-v} and @samp{-d} options.
-The other output files' names are constructed from @var{outfile}
-as described under the @samp{-v} and @samp{-d} options.
+@item -g
+Output a VCG definition of the LALR(1) grammar automaton computed by
+Bison. If the grammar file is @file{foo.y}, the VCG output file will
+be @file{foo.vcg}.
+
+@item --graph=@var{graph-file}
+The behaviour of @var{--graph} is the same than @samp{-g}. The only
+difference is that it has an optionnal argument which is the name of
+the output graph filename.
@end table
-@node Environment Variables, Option Cross Key, Bison Options, Invocation
+@node Environment Variables
@section Environment Variables
@cindex environment variables
@cindex BISON_HAIRY
@end table
-@node Option Cross Key, VMS Invocation, Environment Variables, Invocation
+@node Option Cross Key
@section Option Cross Key
Here is a list of options, alphabetized by long option, to help you find
\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}
\line{ --no-lines \leaderfill -l}
\line{ --no-parser \leaderfill -n}
-\line{ --output-file \leaderfill -o}
+\line{ --output \leaderfill -o}
\line{ --token-table \leaderfill -k}
\line{ --verbose \leaderfill -v}
\line{ --version \leaderfill -V}
@ifinfo
@example
--debug -t
---defines -d
+--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}
--no-lines -l
--no-parser -n
---output-file=@var{outfile} -o @var{outfile}
+--output=@var{outfile} -o @var{outfile}
--token-table -k
--verbose -v
--version -V
@end example
@end ifinfo
-@node VMS Invocation, , Option Cross Key, Invocation
+@node VMS Invocation
@section Invoking Bison under VMS
@cindex invoking Bison under VMS
@cindex VMS
@file{foo.tab.c}. In the above example, the output file
would instead be named @file{foo_tab.c}.
-@node Table of Symbols, Glossary, Invocation, Top
+@node Table of Symbols
@appendix Bison Symbols
@cindex Bison symbols, table of
@cindex symbols in Bison, table of
Macro whose value indicates whether the parser is recovering from a
syntax error. @xref{Action Features, ,Special Features for Use in Actions}.
+@item YYSTACK_USE_ALLOCA
+Macro used to control the use of @code{alloca}. If defined to @samp{0},
+the parser will not use @code{alloca} but @code{malloc} when trying to
+grow its internal stacks. Do @emph{not} define @code{YYSTACK_USE_ALLOCA}
+to anything else.
+
@item YYSTYPE
Macro for the data type of semantic values; @code{int} by default.
@xref{Value Type, ,Data Types of Semantic Values}.
Bison declaration to create a header file meant for the scanner.
@xref{Decl Summary}.
+@item %file-prefix="@var{prefix}"
+Bison declaration to set tge prefix of the output files. @xref{Decl
+Summary}.
+
+@c @item %source_extension
+@c Bison declaration to specify the generated parser output file extension.
+@c @xref{Decl Summary}.
+@c
+@c @item %header_extension
+@c Bison declaration to specify the generated parser header file extension
+@c if required. @xref{Decl Summary}.
+
@item %left
Bison declaration to assign left associativity to token(s).
@xref{Precedence Decl, ,Operator Precedence}.
-@item %no_lines
+@item %name-prefix="@var{prefix}"
+Bison declaration to rename the external symbols. @xref{Decl Summary}.
+
+@item %no-lines
Bison declaration to avoid generating @code{#line} directives in the
parser file. @xref{Decl Summary}.
Bison declaration to assign non-associativity to token(s).
@xref{Precedence Decl, ,Operator Precedence}.
+@item %output="@var{filename}"
+Bison declaration to set the name of the parser file. @xref{Decl
+Summary}.
+
@item %prec
Bison declaration to assign a precedence to a specific rule.
@xref{Contextual Precedence, ,Context-Dependent Precedence}.
-@item %pure_parser
+@item %pure-parser
Bison declaration to request a pure (reentrant) parser.
@xref{Pure Decl, ,A Pure (Reentrant) Parser}.
Bison declaration to declare token(s) without specifying precedence.
@xref{Token Decl, ,Token Type Names}.
-@item %token_table
+@item %token-table
Bison declaration to include a token name table in the parser file.
@xref{Decl Summary}.
@table @samp
@item %%
Delimiter used to separate the grammar rule section from the
-Bison declarations section or the additional C code section.
+Bison declarations section or the epilogue.
@xref{Grammar Layout, ,The Overall Layout of a Bison Grammar}.
@item %@{ %@}
All code listed between @samp{%@{} and @samp{%@}} is copied directly to
-the output file uninterpreted. Such code forms the ``C declarations''
-section of the input file. @xref{Grammar Outline, ,Outline of a Bison
+the output file uninterpreted. Such code forms the prologue of the input
+file. @xref{Grammar Outline, ,Outline of a Bison
Grammar}.
@item /*@dots{}*/
@xref{Rules, ,Syntax of Grammar Rules}.
@end table
-@node Glossary, Copying This Manual, Table of Symbols, Top
+@node Glossary
@appendix Glossary
@cindex glossary
@xref{Language and Grammar, ,Languages and Context-Free Grammars}.
@end table
-@node Copying This Manual, Index, Glossary, Top
+@node Copying This Manual
@appendix Copying This Manual
-
+
@menu
* GNU Free Documentation License:: License for copying this manual.
@end menu
-
+
@include fdl.texi
-@node Index, , Copying This Manual, Top
+@node Index
@unnumbered Index
@printindex cp
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