* NEWS (2.5): Make some minor improvements to wording, and format
entries more consistently.
* doc/bison.texinfo (Language and Grammar): Point out that IELR
and canonical LR are experimental features.
(Decl Summary): In list of %define variables, make wording more
consistent. Improve discussion of using LALR for GLR.
(cherry picked from commit
f1b238df182101b9c9d3808bf2d5e2333e27c50f)
Conflicts:
doc/bison.texinfo
+2010-12-19 Joel E. Denny <jdenny@clemson.edu>
+
+ doc: cleanup.
+ * NEWS (2.5): Make some minor improvements to wording, and format
+ entries more consistently.
+ * doc/bison.texinfo (Language and Grammar): Point out that IELR
+ and canonical LR are experimental features.
+ (Decl Summary): In list of %define variables, make wording more
+ consistent. Improve discussion of using LALR for GLR.
+
2010-12-19 Joel E. Denny <jdenny@clemson.edu>
parse.lac: document.
2010-12-19 Joel E. Denny <jdenny@clemson.edu>
parse.lac: document.
* Changes in version 2.5 (????-??-??):
* Changes in version 2.5 (????-??-??):
-** Named References Support
Historically, Yacc and Bison have supported positional references
($n, $$) to allow access to symbol values from inside of semantic
Historically, Yacc and Bison have supported positional references
($n, $$) to allow access to symbol values from inside of semantic
These features are experimental in this version. More user feedback
will help to stabilize them.
These features are experimental in this version. More user feedback
will help to stabilize them.
-** IELR(1) and Canonical LR(1) Support
+** IELR(1) and canonical LR(1):
IELR(1) is a minimal LR(1) parser table generation algorithm. That
is, given any context-free grammar, IELR(1) generates parser tables
with the full language recognition power of canonical LR(1) but with
IELR(1) is a minimal LR(1) parser table generation algorithm. That
is, given any context-free grammar, IELR(1) generates parser tables
with the full language recognition power of canonical LR(1) but with
- nearly the same number of parser states as LALR(1). This reduction in
- parser states is often an order of magnitude. More importantly,
+ nearly the same number of parser states as LALR(1). This reduction
+ in parser states is often an order of magnitude. More importantly,
because canonical LR(1)'s extra parser states may contain duplicate
conflicts in the case of non-LR(1) grammars, the number of conflicts
for IELR(1) is often an order of magnitude less as well. This can
because canonical LR(1)'s extra parser states may contain duplicate
conflicts in the case of non-LR(1) grammars, the number of conflicts
for IELR(1) is often an order of magnitude less as well. This can
LAC is an experimental feature. More user feedback will help to
stabilize it.
LAC is an experimental feature. More user feedback will help to
stabilize it.
-** Unrecognized %code qualifiers are now an error not a warning.
+** Unrecognized %code qualifiers are now errors not warnings.
-** %define improvements.
+** %define improvements:
-*** Unrecognized variables are now an error not a warning.
+*** Unrecognized variables are now errors not warnings.
*** Multiple invocations for any variable is now an error not a warning.
*** Multiple invocations for any variable is now an error not a warning.
-*** Can now be invoked via the command line.
+*** Can now be invoked via the command line:
Each of these command-line options
Each of these command-line options
quietly override %define, but -D and --define do not. For further
details, see the section "Bison Options" in the Bison manual.
quietly override %define, but -D and --define do not. For further
details, see the section "Bison Options" in the Bison manual.
The following %define variables
The following %define variables
The old names are now deprecated but will be maintained indefinitely
for backward compatibility.
The old names are now deprecated but will be maintained indefinitely
for backward compatibility.
-*** Values no longer need to be quoted in grammar file.
+*** Values no longer need to be quoted in grammar file:
If a %define value is an identifier, it no longer needs to be placed
within quotations marks. For example,
If a %define value is an identifier, it no longer needs to be placed
within quotations marks. For example,
%define api.push-pull push
%define api.push-pull push
+** Grammar symbol names can now contain dashes:
Consistently with directives (such as %error-verbose) and variables
Consistently with directives (such as %error-verbose) and variables
- (e.g. push-pull), symbol names may include dashes in any position,
- similarly to periods and underscores. This is GNU extension over
- POSIX Yacc whose use is reported by -Wyacc, and rejected in Yacc
- mode (--yacc).
+ (e.g. push-pull), grammar symbol names may include dashes in any
+ position, similarly to periods and underscores. This is GNU
+ extension over POSIX Yacc whose use is reported by -Wyacc, and
+ rejected in Yacc mode (--yacc).
-** YYFAIL now produces warnings and Java parsers no longer implement it.
+** YYFAIL now produces warnings and Java parsers no longer implement it:
YYFAIL has existed for many years as an undocumented feature of
deterministic parsers in C generated by Bison. More recently, it was
YYFAIL has existed for many years as an undocumented feature of
deterministic parsers in C generated by Bison. More recently, it was
discussion of how to suppress C preprocessor warnings about YYFAIL
being unused, see the Bison 2.4.2 NEWS entry.
discussion of how to suppress C preprocessor warnings about YYFAIL
being unused, see the Bison 2.4.2 NEWS entry.
-** Temporary hack for adding a semicolon to the user action.
+** Temporary hack for adding a semicolon to the user action:
Previously, Bison appended a semicolon to every user action for
reductions when the output language defaulted to C (specifically, when
Previously, Bison appended a semicolon to every user action for
reductions when the output language defaulted to C (specifically, when
about a missing semicolon where it did not before. Future releases of
Bison will cease to append semicolons entirely.
about a missing semicolon where it did not before. Future releases of
Bison will cease to append semicolons entirely.
-** Character literals not of length one.
+** Character literals not of length one:
Previously, Bison quietly converted all character literals to length
one. For example, without warning, Bison interpreted the operators in
Previously, Bison quietly converted all character literals to length
one. For example, without warning, Bison interpreted the operators in
;
Bison now warns when a character literal is not of length one. In
;
Bison now warns when a character literal is not of length one. In
- some future release, Bison will report an error instead.
+ some future release, Bison will start reporting an error instead.
** Verbose syntax error message fixes:
** Verbose syntax error message fixes:
canonical LR. However, LAC is still experimental and is disabled
by default.
canonical LR. However, LAC is still experimental and is disabled
by default.
-** Destructor calls fixed for lookaheads altered in semantic actions.
+** Destructor calls fixed for lookaheads altered in semantic actions:
Previously for deterministic parsers in C, if a user semantic action
altered yychar, the parser in some cases used the old yychar value to
determine which destructor to call for the lookahead upon a syntax
error or upon parser return. This bug has been fixed.
Previously for deterministic parsers in C, if a user semantic action
altered yychar, the parser in some cases used the old yychar value to
determine which destructor to call for the lookahead upon a syntax
error or upon parser return. This bug has been fixed.
-** C++ parsers use YYRHSLOC
+** C++ parsers use YYRHSLOC:
Similarly to the C parsers, the C++ parsers now define the YYRHSLOC
macro and use it in the default YYLLOC_DEFAULT. You are encouraged
Similarly to the C parsers, the C++ parsers now define the YYRHSLOC
macro and use it in the default YYLLOC_DEFAULT. You are encouraged
-** YYLLOC_DEFAULT in C++
+** YYLLOC_DEFAULT in C++:
The default implementation of YYLLOC_DEFAULT used to be issued in
the header file. It is now output in the implementation file, after
The default implementation of YYLLOC_DEFAULT used to be issued in
the header file. It is now output in the implementation file, after
restrictions of @acronym{LALR}(1), which is hard to explain simply.
@xref{Mystery Conflicts, ,Mysterious Reduce/Reduce Conflicts}, for
more information on this.
restrictions of @acronym{LALR}(1), which is hard to explain simply.
@xref{Mystery Conflicts, ,Mysterious Reduce/Reduce Conflicts}, for
more information on this.
-To escape these additional restrictions, you can request
-@acronym{IELR}(1) or canonical @acronym{LR}(1) parser tables.
+As an experimental feature, you can escape these additional restrictions by
+requesting @acronym{IELR}(1) or canonical @acronym{LR}(1) parser tables.
@xref{Decl Summary,,lr.type}, to learn how.
@cindex @acronym{GLR} parsing
@xref{Decl Summary,,lr.type}, to learn how.
@cindex @acronym{GLR} parsing
@itemize @bullet
@item Language(s): C (deterministic parsers only)
@itemize @bullet
@item Language(s): C (deterministic parsers only)
-@item Purpose: Requests a pull parser, a push parser, or both.
+@item Purpose: Request a pull parser, a push parser, or both.
@xref{Push Decl, ,A Push Parser}.
(The current push parsing interface is experimental and may evolve.
More user feedback will help to stabilize it.)
@xref{Push Decl, ,A Push Parser}.
(The current push parsing interface is experimental and may evolve.
More user feedback will help to stabilize it.)
@itemize @bullet
@item Language(s): all
@itemize @bullet
@item Language(s): all
-@item Purpose: Requests that Bison allow unreachable parser states to remain in
-the parser tables.
+@item Purpose: Request that Bison allow unreachable parser states to
+remain in the parser tables.
Bison considers a state to be unreachable if there exists no sequence of
transitions from the start state to that state.
A state can become unreachable during conflict resolution if Bison disables a
Bison considers a state to be unreachable if there exists no sequence of
transitions from the start state to that state.
A state can become unreachable during conflict resolution if Bison disables a
@itemize @bullet
@item Language(s): all
@itemize @bullet
@item Language(s): all
-@item Purpose: Specifies the type of parser tables within the
+@item Purpose: Specify the type of parser tables within the
@acronym{LR}(1) family.
(This feature is experimental.
More user feedback will help to stabilize it.)
@acronym{LR}(1) family.
(This feature is experimental.
More user feedback will help to stabilize it.)
to alter the language accepted by the parser.
@acronym{LALR} parser tables are the smallest parser tables Bison can
currently generate, so they may be preferable.
to alter the language accepted by the parser.
@acronym{LALR} parser tables are the smallest parser tables Bison can
currently generate, so they may be preferable.
+Nevertheless, once you begin to resolve conflicts statically,
+@acronym{GLR} begins to behave more like a deterministic parser, and so
+@acronym{IELR} and canonical @acronym{LR} can be helpful to avoid
+@acronym{LALR}'s mysterious behavior.
@item Occasionally during development, an especially malformed grammar
with a major recurring flaw may severely impede the @acronym{IELR} or
@item Occasionally during development, an especially malformed grammar
with a major recurring flaw may severely impede the @acronym{IELR} or
@itemize
@item Languages(s): C++
@itemize
@item Languages(s): C++
-@item Purpose: Specifies the namespace for the parser class.
+@item Purpose: Specify the namespace for the parser class.
For example, if you specify:
@smallexample
For example, if you specify:
@smallexample
projects / bison.git / commitdiff
