This manual (@value{UPDATED}) is for GNU Bison (version
@value{VERSION}), the GNU parser generator.
-Copyright @copyright{} 1988-1993, 1995, 1998-2012 Free Software
+Copyright @copyright{} 1988-1993, 1995, 1998-2013 Free Software
Foundation, Inc.
@quotation
@example
/* Reverse polish notation calculator. */
+@group
%@{
#define YYSTYPE double
#include <stdio.h>
int yylex (void);
void yyerror (char const *);
%@}
+@end group
%token NUM
%type <val> exp
@group
-%right '='
+%precedence '='
%left '-' '+'
%left '*' '/'
%precedence NEG /* negation--unary minus */
@code{%union} declaration.
@example
+@group
%@{
#define _GNU_SOURCE
#include <stdio.h>
#include "ptypes.h"
%@}
+@end group
+@group
%union @{
long int n;
tree t; /* @r{@code{tree} is defined in @file{ptypes.h}.} */
@}
+@end group
+@group
%@{
static void print_token_value (FILE *, int, YYSTYPE);
#define YYPRINT(F, N, L) print_token_value (F, N, L)
%@}
+@end group
@dots{}
@end example
Look again at the example of the previous section:
@example
+@group
%@{
#define _GNU_SOURCE
#include <stdio.h>
#include "ptypes.h"
%@}
+@end group
+@group
%union @{
long int n;
tree t; /* @r{@code{tree} is defined in @file{ptypes.h}.} */
@}
+@end group
+@group
%@{
static void print_token_value (FILE *, int, YYSTYPE);
#define YYPRINT(F, N, L) print_token_value (F, N, L)
%@}
+@end group
@dots{}
@end example
@} YYLTYPE;
@}
+@group
%union @{
long int n;
tree t; /* @r{@code{tree} is defined in @file{ptypes.h}.} */
@}
+@end group
+@group
%code @{
static void print_token_value (FILE *, int, YYSTYPE);
#define YYPRINT(F, N, L) print_token_value (F, N, L)
static void trace_token (enum yytokentype token, YYLTYPE loc);
@}
+@end group
@dots{}
@end example
skeleton (@pxref{Decl Summary,,%language}, @pxref{Decl
Summary,,%skeleton}).
Unaccepted @var{variable}s produce an error.
-Some of the accepted @var{variable}s are:
+Some of the accepted @var{variable}s are described below.
-@table @code
-@c ================================================== api.namespace
-@item api.namespace
-@findex %define api.namespace
+@deffn Directive {%define api.namespace} "@var{namespace}"
@itemize
@item Languages(s): C++
The parser namespace is @code{foo} and @code{yylex} is referenced as
@code{bar::lex}.
@end itemize
-@c namespace
+@end deffn
+@c api.namespace
@c ================================================== api.location.type
-@item @code{api.location.type}
-@findex %define api.location.type
+@deffn {Directive} {%define api.location.type} @var{type}
@itemize @bullet
@item Language(s): C++, Java
@item Default Value: none
-@item History: introduced in Bison 2.7
+@item History:
+Introduced in Bison 2.7 for C, C++ and Java. Introduced under the name
+@code{location_type} for C++ in Bison 2.5 and for Java in Bison 2.4.
@end itemize
+@end deffn
@c ================================================== api.prefix
-@item api.prefix
-@findex %define api.prefix
+@deffn {Directive} {%define api.prefix} @var{prefix}
@itemize @bullet
@item Language(s): All
@item History: introduced in Bison 2.6
@end itemize
+@end deffn
@c ================================================== api.pure
-@item api.pure
-@findex %define api.pure
+@deffn Directive {%define api.pure}
@itemize @bullet
@item Language(s): C
@item Default Value: @code{false}
-@item History: the @code{full} value was introduced in Bison 2.7
+@item History:
+the @code{full} value was introduced in Bison 2.7
@end itemize
+@end deffn
@c api.pure
@c ================================================== api.push-pull
-@item api.push-pull
-@findex %define api.push-pull
+@deffn Directive {%define api.push-pull} @var{kind}
@itemize @bullet
@item Language(s): C (deterministic parsers only)
@item Default Value: @code{pull}
@end itemize
+@end deffn
@c api.push-pull
@c ================================================== api.token.constructor
-@item api.token.constructor
-@findex %define api.token.constructor
+@deffn Directive {%define api.token.constructor}
@itemize @bullet
@item Language(s):
@item History:
introduced in Bison 2.8
@end itemize
+@end deffn
@c api.token.constructor
@c ================================================== api.token.prefix
-@item api.token.prefix
-@findex %define api.token.prefix
+@deffn Directive {%define api.token.prefix} @var{prefix}
@itemize
@item Languages(s): all
@item History:
introduced in Bison 2.8
@end itemize
+@end deffn
@c api.token.prefix
+@c ================================================== api.value.type
+@deffn Directive {%define api.value.type} @var{type}
+@itemize @bullet
+@item Language(s):
+C++
+
+@item Purpose:
+Request variant-based semantic values.
+@xref{C++ Variants}.
+
+@item Default Value:
+FIXME:
+@item History:
+introduced in Bison 2.8. Was introduced for Java only in 2.3b as
+@code{stype}.
+@end itemize
+@end deffn
+@c api.value.type
+
+
+@c ================================================== location_type
+@deffn Directive {%define location_type}
+Obsoleted by @code{api.location.type} since Bison 2.7.
+@end deffn
+
+
@c ================================================== lr.default-reduction
-@item lr.default-reduction
-@findex %define lr.default-reduction
+@deffn Directive {%define lr.default-reduction} @var{when}
@itemize @bullet
@item Language(s): all
introduced as @code{lr.default-reduction} in 2.5, renamed as
@code{lr.default-reduction} in 2.8.
@end itemize
+@end deffn
@c ============================================ lr.keep-unreachable-state
-@item lr.keep-unreachable-state
-@findex %define lr.keep-unreachable-state
+@deffn Directive {%define lr.keep-unreachable-state}
@itemize @bullet
@item Language(s): all
remain in the parser tables. @xref{Unreachable States}.
@item Accepted Values: Boolean
@item Default Value: @code{false}
-@end itemize
+@item History:
introduced as @code{lr.keep_unreachable_states} in 2.3b, renamed as
@code{lr.keep-unreachable-states} in 2.5, and as
@code{lr.keep-unreachable-state} in 2.8.
+@end itemize
+@end deffn
@c lr.keep-unreachable-state
@c ================================================== lr.type
-@item lr.type
-@findex %define lr.type
+@deffn Directive {%define lr.type} @var{type}
@itemize @bullet
@item Language(s): all
@item Default Value: @code{lalr}
@end itemize
-
+@end deffn
@c ================================================== namespace
-@item namespace
-@findex %define namespace
+@deffn Directive %define namespace @var{namespace}
Obsoleted by @code{api.namespace}
@c namespace
-
+@end deffn
@c ================================================== parse.assert
-@item parse.assert
-@findex %define parse.assert
+@deffn Directive {%define parse.assert}
@itemize
@item Languages(s): C++
@item Default Value: @code{false}
@end itemize
+@end deffn
@c parse.assert
@c ================================================== parse.error
-@item parse.error
-@findex %define parse.error
+@deffn Directive {%define parse.error}
@itemize
@item Languages(s):
all
@item Default Value:
@code{simple}
@end itemize
+@end deffn
@c parse.error
@c ================================================== parse.lac
-@item parse.lac
-@findex %define parse.lac
+@deffn Directive {%define parse.lac}
@itemize
@item Languages(s): C (deterministic parsers only)
@item Accepted Values: @code{none}, @code{full}
@item Default Value: @code{none}
@end itemize
+@end deffn
@c parse.lac
@c ================================================== parse.trace
-@item parse.trace
-@findex %define parse.trace
+@deffn Directive {%define parse.trace}
@itemize
@item Languages(s): C, C++, Java
@item Default Value: @code{false}
@end itemize
+@end deffn
@c parse.trace
-@c ================================================== variant
-@item variant
-@findex %define variant
-
-@itemize @bullet
-@item Language(s):
-C++
-
-@item Purpose:
-Request variant-based semantic values.
-@xref{C++ Variants}.
-
-@item Accepted Values:
-Boolean.
-
-@item Default Value:
-@code{false}
-@end itemize
-@c variant
-@end table
-
-
@node %code Summary
@subsection %code Summary
@findex %code
@code{YYDEBUG} (not renamed) is used as a default value:
@example
-/* Enabling traces. */
+/* Debug traces. */
#ifndef CDEBUG
# if defined YYDEBUG
# if YYDEBUG
Deprecated constructs whose support will be removed in future versions of
Bison.
+@item precedence
+Useless precedence and associativity directives. Disabled by default.
+
+Consider for instance the following grammar:
+
+@example
+@group
+%nonassoc "="
+%left "+"
+%left "*"
+%precedence "("
+@end group
+%%
+@group
+stmt:
+ exp
+| "var" "=" exp
+;
+@end group
+
+@group
+exp:
+ exp "+" exp
+| exp "*" "num"
+| "(" exp ")"
+| "num"
+;
+@end group
+@end example
+
+Bison reports:
+
+@c cannot leave the location and the [-Wprecedence] for lack of
+@c width in PDF.
+@example
+@group
+warning: useless precedence and associativity for "="
+ %nonassoc "="
+ ^^^
+@end group
+@group
+warning: useless associativity for "*", use %precedence
+ %left "*"
+ ^^^
+@end group
+@group
+warning: useless precedence for "("
+ %precedence "("
+ ^^^
+@end group
+@end example
+
+One would get the exact same parser with the following directives instead:
+
+@example
+@group
+%left "+"
+%precedence "*"
+@end group
+@end example
+
@item other
All warnings not categorized above. These warnings are enabled by default.
exp: exp '+' exp @{ $exp = $1 + $2; @};
@end example
-When invoked with @option{-fcaret}, Bison will report:
+When invoked with @option{-fcaret} (or nothing), Bison will report:
@example
@group
@end group
@end example
+Whereas, when invoked with @option{-fno-caret}, Bison will only report:
+
+@example
+@group
+in.y:3.20-23: error: ambiguous reference: ‘$exp’
+in.y:3.1-3: refers to: $exp at $$
+in.y:3.6-8: refers to: $exp at $1
+in.y:3.14-16: refers to: $exp at $3
+in.y:3.32-33: error: $2 of ‘exp’ has no declared type
+@end group
+@end example
+
+This option is activated by default.
+
@end table
@end table
@node C++ Variants
@subsubsection C++ Variants
-Starting with version 2.6, Bison provides a @emph{variant} based
-implementation of semantic values for C++. This alleviates all the
-limitations reported in the previous section, and in particular, object
-types can be used without pointers.
+Bison provides a @emph{variant} based implementation of semantic values for
+C++. This alleviates all the limitations reported in the previous section,
+and in particular, object types can be used without pointers.
To enable variant-based semantic values, set @code{%define} variable
@code{variant} (@pxref{%define Summary,, variant}). Once this defined,
type on all platforms, alignments are enforced for @code{double} whatever
types are actually used. This may waste space in some cases.
-@item
-Our implementation is not conforming with strict aliasing rules. Alias
-analysis is a technique used in optimizing compilers to detect when two
-pointers are disjoint (they cannot ``meet''). Our implementation breaks
-some of the rules that G++ 4.4 uses in its alias analysis, so @emph{strict
-alias analysis must be disabled}. Use the option
-@option{-fno-strict-aliasing} to compile the generated parser.
-
@item
There might be portability issues we are not aware of.
@end itemize
@node Complete Symbols
@subsubsection Complete Symbols
-If you specified both @code{%define variant} and
+If you specified both @code{%define api.value.type variant} and
@code{%define api.token.constructor},
the @code{parser} class also defines the class @code{parser::symbol_type}
which defines a @emph{complete} symbol, aggregating its type (i.e., the
@noindent
@findex %define api.token.constructor
-@findex %define variant
+@findex %define api.value.type variant
This example will use genuine C++ objects as semantic values, therefore, we
require the variant-based interface. To make sure we properly use it, we
enable assertions. To fully benefit from type-safety and more natural
@comment file: calc++-parser.yy
@example
%define api.token.constructor
+%define api.value.type variant
%define parse.assert
-%define variant
@end example
@noindent
@comment file: calc++-scanner.ll
@example
-%option noyywrap nounput batch debug
+%option noyywrap nounput batch debug noinput
@end example
@noindent
By default, the semantic stack is declared to have @code{Object} members,
which means that the class types you specify can be of any class.
To improve the type safety of the parser, you can declare the common
-superclass of all the semantic values using the @samp{%define stype}
+superclass of all the semantic values using the @samp{%define api.value.type}
directive. For example, after the following declaration:
@example
-%define stype "ASTNode"
+%define api.value.type "ASTNode"
@end example
@noindent
@deftypemethod {Lexer} {Object} getLVal ()
Return the semantic value of the last token that yylex returned.
-The return type can be changed using @samp{%define stype
+The return type can be changed using @samp{%define api.value.type
"@var{class-name}".}
@end deftypemethod
@defvar $$
The semantic value for the grouping made by the current rule. As a
value, this is in the base type (@code{Object} or as specified by
-@samp{%define stype}) as in not cast to the declared subtype because
+@samp{%define api.value.type}) as in not cast to the declared subtype because
casts are not allowed on the left-hand side of Java assignments.
Use an explicit Java cast if the correct subtype is needed.
@xref{Java Semantic Values}.
@item
Java lacks unions, so @code{%union} has no effect. Instead, semantic
values have a common base type: @code{Object} or as specified by
-@samp{%define stype}. Angle brackets on @code{%token}, @code{type},
+@samp{%define api.value.type}. Angle brackets on @code{%token}, @code{type},
@code{$@var{n}} and @code{$$} specify subtypes rather than fields of
an union. The type of @code{$$}, even with angle brackets, is the base
type since Java casts are not allow on the left-hand side of assignments.
@xref{Java Bison Interface}.
@end deffn
-@deffn {Directive} {%define stype} "@var{class}"
+@deffn {Directive} {%define api.value.type} "@var{class}"
The base type of semantic values. Default is @code{Object}.
@xref{Java Semantic Values}.
@end deffn
@code{yylex}}.
@end deffn
-@deffn {Macro} YYLEX_PARAM
-An obsolete macro for specifying an extra argument (or list of extra
-arguments) for @code{yyparse} to pass to @code{yylex}. The use of this
-macro is deprecated, and is supported only for Yacc like parsers.
-@xref{Pure Calling,, Calling Conventions for Pure Parsers}.
-@end deffn
-
@deffn {Variable} yylloc
External variable in which @code{yylex} should place the line and column
numbers associated with a token. (In a pure parser, it is a local
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