"initial push" (corresponding to an hypothetical beginning-of-file).
And let lalr1.cc honor %initial-action.
* doc/bison.texinfo (Initial Action Decl): Clarify, and add an
example.
* data/lalr1.cc (Parser::initlocation_): Remove, bad experiment.
(Parser::Parser): Remove the ctor that used to initialize it.
(Parser::parse): Like in the other skeletons, issue the "starting
parse" message before any action.
Honor %initial-action.
Initialize the stacks with the lookahead.
* data/yacc.c: Let $$ and @$ in %initial-action designate the
look-ahead.
Push them in the stacks.
* tests/actions.at, tests/calc.at: Adjust the C++ ctor invocations.
+2004-09-20 Akim Demaille <akim@epita.fr>
+
+ Let the initial-action act on the look-ahead, and use it for the
+ "initial push" (corresponding to an hypothetical beginning-of-file).
+ And let lalr1.cc honor %initial-action.
+
+ * doc/bison.texinfo (Initial Action Decl): Clarify, and add an
+ example.
+ * data/lalr1.cc (Parser::initlocation_): Remove, bad experiment.
+ (Parser::Parser): Remove the ctor that used to initialize it.
+ (Parser::parse): Like in the other skeletons, issue the "starting
+ parse" message before any action.
+ Honor %initial-action.
+ Initialize the stacks with the lookahead.
+ * data/yacc.c: Let $$ and @$ in %initial-action designate the
+ look-ahead.
+ Push them in the stacks.
+ * tests/actions.at, tests/calc.at: Adjust the C++ ctor invocations.
+
2004-09-20 Akim Demaille <akim@epita.fr>
* doc/bison.texinfo (Initial Action Decl): New.
typedef Stack< SemanticType > SemanticStack;
typedef Stack< LocationType > LocationStack;
-#if YYLSP_NEEDED
- ]b4_parser_class_name[ (bool debug,
- LocationType initlocation][]b4_param[]b4_parse_param_decl[) :
- ]b4_constructor[][debug_ (debug),
- cdebug_ (std::cerr),
- initlocation_ (initlocation)]b4_parse_param_cons[
-#else
]b4_parser_class_name[ (bool debug][]b4_param[]b4_parse_param_decl[) :
]b4_constructor[][debug_ (debug),
cdebug_ (std::cerr)]b4_parse_param_cons[
-#endif
{
}
/* Message. */
std::string message;
- /* Semantic value and location of look-ahead token. */
+ /// Semantic value of the look-ahead.
SemanticType value;
+ /// Location of the look-ahead.
LocationType location;
/// The locations where the error started and ended.
Location error_range_[2];
- /* @@$ and $$. */
+ /// $$.
SemanticType yyval;
+ /// @@$.
LocationType yyloc;
-
- /* Initial location. */
- LocationType initlocation_;
]b4_parse_param_vars[
};
}
int
yy::]b4_parser_class_name[::parse ()
{
+ YYCDEBUG << "Starting parse" << std::endl;
+
nerrs_ = 0;
errstatus_ = 0;
- /* Initialize the stacks. The initial state will be pushed in
+ /* Start. */
+ state_ = 0;
+ looka_ = empty_;
+
+]m4_ifdef([b4_initial_action], [
+m4_pushdef([b4_at_dollar], [location])dnl
+m4_pushdef([b4_dollar_dollar], [value])dnl
+ /* User initialization code. */
+ b4_initial_action
+m4_popdef([b4_dollar_dollar])dnl
+m4_popdef([b4_at_dollar])dnl
+/* Line __line__ of yacc.c. */
+b4_syncline([@oline@], [@ofile@])])dnl
+
+[ /* Initialize the stacks. The initial state will be pushed in
yynewstate, since the latter expects the semantical and the
location values to have been already stored, initialize these
stacks with a primary value. */
state_stack_ = StateStack (0);
- semantic_stack_ = SemanticStack (1);
- location_stack_ = LocationStack (1);
-
- /* Start. */
- state_ = 0;
- looka_ = empty_;
-#if YYLSP_NEEDED
- location = initlocation_;
-#endif
- YYCDEBUG << "Starting parse" << std::endl;
+ semantic_stack_ = SemanticStack (0);
+ location_stack_ = LocationStack (0);
+ semantic_stack_.push (value);
+ location_stack_.push (location);
/* New state. */
yynewstate:
]b4_location_if([[ yylsp = yyls;
#if YYLTYPE_IS_TRIVIAL
/* Initialize the default location before parsing starts. */
- yyls[0].first_line = yyls[0].last_line = 1;
- yyls[0].first_column = yyls[0].last_column = 0;
+ yylloc.first_line = yylloc.last_line = 1;
+ yylloc.first_column = yylloc.last_column = 0;
#endif
]])
m4_ifdef([b4_initial_action], [
-m4_pushdef([b4_at_dollar], [(*yylsp)])dnl
-m4_pushdef([b4_dollar_dollar], [(*yyvsp)])dnl
+m4_pushdef([b4_at_dollar], [(yylloc)])dnl
+m4_pushdef([b4_dollar_dollar], [(yylval)])dnl
/* User initialization code. */
b4_initial_action
m4_popdef([b4_dollar_dollar])dnl
m4_popdef([b4_at_dollar])dnl
/* Line __line__ of yacc.c. */
b4_syncline([@oline@], [@ofile@])])dnl
-
+[
+ yyvsp[0] = yylval;
+]b4_location_if([[ yylsp[0] = yylloc;
+]])
[ goto yysetstate;
/*------------------------------------------------------------.
@deffn {Directive} %initial-action @{ @var{code} @}
@findex %initial-action
Declare that the @var{code} must be invoked before parsing each time
-@code{yyparse} is called. The @var{code} may use @code{@@$} to
-designate the initial location, and the @code{%parse-param}.
+@code{yyparse} is called. The @var{code} may use @code{$$} and
+@code{@@$} --- initial value and location of the look-ahead --- and the
+@code{%parse-param}.
@end deffn
+For instance, if your locations use a file name, you may use
+
+@example
+%parse-param @{ const char *filename @};
+%initial-action
+@{
+ @@$.begin.filename = @@$.end.filename = filename;
+@};
+@end example
+
@node Destructor Decl
@subsection Freeing Discarded Symbols
@item
incoming terminals during the second phase of error recovery,
@item
-the current lookahead when the parser aborts (either via an explicit
+the current look-ahead when the parser aborts (either via an explicit
call to @code{YYABORT}, or as a consequence of a failed error recovery).
@end itemize
@c FIXME: C++ output.
Because of semantical differences between C and C++, the
-@acronym{LALR}(1) parsers
-in C produced by Bison by compiled as C++ cannot grow. In this precise
-case (compiling a C parser as C++) you are suggested to grow
-@code{YYINITDEPTH}. In the near future, a C++ output output will be
-provided which addresses this issue.
+@acronym{LALR}(1) parsers in C produced by Bison by compiled as C++
+cannot grow. In this precise case (compiling a C parser as C++) you are
+suggested to grow @code{YYINITDEPTH}. In the near future, a C++ output
+output will be provided which addresses this issue.
@node Error Recovery
@chapter Error Recovery
How can I generate parsers in C++?
@end display
-We are working on a C++ output for Bison, but unfortunately, for lack
-of time, the skeleton is not finished. It is functional, but in
-numerous respects, it will require additional work which @emph{might}
-break backward compatibility. Since the skeleton for C++ is not
-documented, we do not consider ourselves bound to this interface,
-nevertheless, as much as possible we will try to keep compatibility.
-
-Another possibility is to use the regular C parsers, and to compile
-them with a C++ compiler. This works properly, provided that you bear
-some simple C++ rules in mind, such as not including ``real classes''
-(i.e., structure with constructors) in unions. Therefore, in the
-@code{%union}, use pointers to classes, or better yet, a single
-pointer type to the root of your lexical/syntactic hierarchy.
+We are working on a C++ output for Bison, but unfortunately, for lack of
+time, the skeleton is not finished. It is functional, but in numerous
+respects, it will require additional work which @emph{might} break
+backward compatibility. Since the skeleton for C++ is not documented,
+we do not consider ourselves bound to this interface, nevertheless, as
+much as possible we will try to keep compatibility.
+
+Another possibility is to use the regular C parsers, and to compile them
+with a C++ compiler. This works properly, provided that you bear some
+simple C++ rules in mind, such as not including ``real classes'' (i.e.,
+structure with constructors) in unions. Therefore, in the
+@code{%union}, use pointers to classes.
@node Implementing Gotos/Loops
int
yyparse ()
{
- yy::Parser parser (yydebug, yy::Location ());
+ yy::Parser parser (yydebug);
return parser.parse ();
}
],
int
yyparse (AT_PARAM_IF([semantic_value *result, int *count]))
{
- yy::Parser parser (!!YYDEBUG[]AT_LOCATION_IF([, yy::Location ()])AT_PARAM_IF([, result, count]));
+ yy::Parser parser (!!YYDEBUG[]AT_PARAM_IF([, result, count]));
return parser.parse ();
}
],
projects / bison.git / commitdiff
