* Changes in version 2.5 (????-??-??):
-** Named References Support
+** Named references:
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.
-** 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
- 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
LAC is an experimental feature. More user feedback will help to
stabilize it.
-** Unrecognized %code qualifiers are now an error not a warning.
+** Grammar symbol names can now contain dashes:
-** %define improvements.
-
-*** Unrecognized variables are now an error not a warning.
+ Consistently with directives (such as %error-verbose) and variables
+ (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).
-*** Multiple invocations for any variable is now an error not a warning.
+** %define improvements:
-*** Can now be invoked via the command line.
+*** Can now be invoked via the command line:
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.
-*** Variables renamed.
+*** Variables renamed:
The following %define variables
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,
%define api.push-pull push
-** Symbol names.
+*** Unrecognized variables are now errors not warnings.
- 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).
+*** Multiple invocations for any variable is now an error not a warning.
+
+** Unrecognized %code qualifiers are now errors not warnings.
+
+** 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
+ the following grammar to be the same token:
+
+ exp: exp '++'
+ | exp '+' exp
+ ;
-** YYFAIL now produces warnings and Java parsers no longer implement it.
+ Bison now warns when a character literal is not of length one. In
+ some future release, Bison will start reporting an error instead.
+
+** 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.
+
+** 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
+ to use it. If, for instance, your location structure has "first"
+ and "last" members, instead of
+
+ # define YYLLOC_DEFAULT(Current, Rhs, N) \
+ do \
+ if (N) \
+ { \
+ (Current).first = (Rhs)[1].location.first; \
+ (Current).last = (Rhs)[N].location.last; \
+ } \
+ else \
+ { \
+ (Current).first = (Current).last = (Rhs)[0].location.last; \
+ } \
+ while (false)
+
+ use:
+
+ # define YYLLOC_DEFAULT(Current, Rhs, N) \
+ do \
+ if (N) \
+ { \
+ (Current).first = YYRHSLOC (Rhs, 1).first; \
+ (Current).last = YYRHSLOC (Rhs, N).last; \
+ } \
+ else \
+ { \
+ (Current).first = (Current).last = YYRHSLOC (Rhs, 0).last; \
+ } \
+ while (false)
+
+** 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 user %code sections so that its #ifndef guard does not try to
+ override the user's YYLLOC_DEFAULT if provided.
+
+** 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
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
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.
-
- Previously, Bison quietly converted all character literals to length
- one. For example, without warning, Bison interpreted the operators in
- the following grammar to be the same token:
-
- exp: exp '++'
- | exp '+' exp
- ;
-
- Bison now warns when a character literal is not of length one. In
- some future release, Bison will report an error instead.
-
** Verbose syntax error message fixes:
When %error-verbose or `#define YYERROR_VERBOSE' is specified,
canonical LR. However, LAC is still experimental and is disabled
by default.
-** 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.
-
-** 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
- to use it. If, for instance, your location structure has "first"
- and "last" members, instead of
-
- # define YYLLOC_DEFAULT(Current, Rhs, N) \
- do \
- if (N) \
- { \
- (Current).first = (Rhs)[1].location.first; \
- (Current).last = (Rhs)[N].location.last; \
- } \
- else \
- { \
- (Current).first = (Current).last = (Rhs)[0].location.last; \
- } \
- while (false)
-
- use:
-
- # define YYLLOC_DEFAULT(Current, Rhs, N) \
- do \
- if (N) \
- { \
- (Current).first = YYRHSLOC (Rhs, 1).first; \
- (Current).last = YYRHSLOC (Rhs, N).last; \
- } \
- else \
- { \
- (Current).first = (Current).last = YYRHSLOC (Rhs, 0).last; \
- } \
- while (false)
-
-** 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 user %code sections so that its #ifndef guard does not try to
- override the user's YYLLOC_DEFAULT if provided.
-
* Changes in version 2.4.3 (2010-08-05):
** Bison now obeys -Werror and --warnings=error for warnings about
-----
-Copyright (C) 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003,
-2004, 2005, 2006, 2007, 2008, 2009, 2010 Free Software Foundation,
-Inc.
+Copyright (C) 1995-2011 Free Software Foundation, Inc.
This file is part of Bison, the GNU Parser Generator.
projects / bison.git / blobdiff