Update README.

[bison.git] / NEWS

diff --git a/NEWS b/NEWS
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+++ b/NEWS
@@ -1,23 +1,142 @@
 Bison News
 ----------
 
 Bison News
 ----------
 

-Changes in version 2.3a+ (????-??-??):
+Changes in version ?.? (????-??-??):
+
+*
+
+Changes in version 2.3b (2008-05-27):
+
+* The quotes around NAME that used to be required in the following directive
+  are now deprecated:
+
+    %define NAME "VALUE"
+
+* The directive `%pure-parser' is now deprecated in favor of:
+
+    %define api.pure
+
+  which has the same effect except that Bison is more careful to warn about
+  unreasonable usage in the latter case.
+
+* Push Parsing
+
+  Bison can now generate an LALR(1) parser in C with a push interface.  That
+  is, instead of invoking `yyparse', which pulls tokens from `yylex', you can
+  push one token at a time to the parser using `yypush_parse', which will
+  return to the caller after processing each token.  By default, the push
+  interface is disabled.  Either of the following directives will enable it:
+
+    %define api.push_pull "push" // Just push; does not require yylex.
+    %define api.push_pull "both" // Push and pull; requires yylex.
+
+  See the new section `A Push Parser' in the Bison manual for details.
+
+  The current push parsing interface is experimental and may evolve.  More user
+  feedback will help to stabilize it.

 
 * The -g and --graph options now output graphs in Graphviz DOT format,
 
 * The -g and --graph options now output graphs in Graphviz DOT format,

-  not VCG format.
+  not VCG format.  Like --graph, -g now also takes an optional FILE argument
+  and thus cannot be bundled with other short options.
+
+* Java
+
+  Bison can now generate an LALR(1) parser in Java.  The skeleton is
+  `data/lalr1.java'.  Consider using the new %language directive instead of
+  %skeleton to select it.
+
+  See the new section `Java Parsers' in the Bison manual for details.
+
+  The current Java interface is experimental and may evolve.  More user
+  feedback will help to stabilize it.
+
+* %language
+
+  This new directive specifies the programming language of the generated
+  parser, which can be C (the default), C++, or Java.  Besides the skeleton
+  that Bison uses, the directive affects the names of the generated files if
+  the grammar file's name ends in ".y".
+
+* XML Automaton Report
+
+  Bison can now generate an XML report of the LALR(1) automaton using the new
+  `--xml' option.  The current XML schema is experimental and may evolve.  More
+  user feedback will help to stabilize it.

 
 * The grammar file may now specify the name of the parser header file using
   %defines.  For example:
 
     %defines "parser.h"
 
 
 * The grammar file may now specify the name of the parser header file using
   %defines.  For example:
 
     %defines "parser.h"
 

-* The `=' that used to be required in the following declarations is now
+* When reporting useless rules, useless nonterminals, and unused terminals,
+  Bison now employs the terms "useless in grammar" instead of "useless",
+  "useless in parser" instead of "never reduced", and "unused in grammar"
+  instead of "unused".
+
+* Unreachable State Removal
+
+  Previously, Bison sometimes generated parser tables containing unreachable
+  states.  A state can become unreachable during conflict resolution if Bison
+  disables a shift action leading to it from a predecessor state.  Bison now:
+
+    1. Removes unreachable states.
+
+    2. Does not report any conflicts that appeared in unreachable states.
+       WARNING: As a result, you may need to update %expect and %expect-rr
+       directives in existing grammar files.
+
+    3. For any rule used only in such states, Bison now reports the rule as
+       "useless in parser due to conflicts".
+
+  This feature can be disabled with the following directive:
+
+    %define lr.keep_unreachable_states
+
+  See the %define entry in the `Bison Declaration Summary' in the Bison manual
+  for further discussion.
+
+* Lookahead Set Correction in the `.output' Report
+
+  When instructed to generate a `.output' file including lookahead sets
+  (using `--report=lookahead', for example), Bison now prints each reduction's
+  lookahead set only next to the associated state's one item that (1) is
+  associated with the same rule as the reduction and (2) has its dot at the end
+  of its RHS.  Previously, Bison also erroneously printed the lookahead set
+  next to all of the state's other items associated with the same rule.  This
+  bug affected only the `.output' file and not the generated parser source
+  code.
+
+* --report-file=FILE is a new option to override the default `.output' file
+  name.
+
+* The `=' that used to be required in the following directives is now

   deprecated:
 
     %file-prefix "parser"
     %name-prefix "c_"
     %output "parser.c"
 
   deprecated:
 
     %file-prefix "parser"
     %name-prefix "c_"
     %output "parser.c"
 

+* An Alternative to `%{...%}' -- `%code QUALIFIER {CODE}'
+
+  Bison 2.3a provided a new set of directives as a more flexible alternative to
+  the traditional Yacc prologue blocks.  Those have now been consolidated into
+  a single %code directive with an optional qualifier field, which identifies
+  the purpose of the code and thus the location(s) where Bison should generate
+  it:
+
+    1. `%code          {CODE}' replaces `%after-header  {CODE}'
+    2. `%code requires {CODE}' replaces `%start-header  {CODE}'
+    3. `%code provides {CODE}' replaces `%end-header    {CODE}'
+    4. `%code top      {CODE}' replaces `%before-header {CODE}'
+
+  See the %code entries in section `Bison Declaration Summary' in the Bison
+  manual for a summary of the new functionality.  See the new section `Prologue
+  Alternatives' for a detailed discussion including the advantages of %code
+  over the traditional Yacc prologues.
+
+  The prologue alternatives are experimental.  More user feedback will help to
+  determine whether they should become permanent features.
+

 * Revised warning: unset or unused mid-rule values
 
   Since Bison 2.2, Bison has warned about mid-rule values that are set but not
 * Revised warning: unset or unused mid-rule values
 
   Since Bison 2.2, Bison has warned about mid-rule values that are set but not


@@ -35,10 +154,12 @@ Changes in version 2.3a+ (????-??-??):
   sometimes prove to be false alarms in existing grammars employing the Yacc
   constructs $0 or $-N (where N is some positive integer).
 
   sometimes prove to be false alarms in existing grammars employing the Yacc
   constructs $0 or $-N (where N is some positive integer).
 

-  To enable these warnings, specify the flag `--warnings=midrule-values' or
+  To enable these warnings, specify the option `--warnings=midrule-values' or

   `-W', which is a synonym for `--warnings=all'.
 
   `-W', which is a synonym for `--warnings=all'.
 

-* Bison now recognizes two separate kinds of default %destructor's and
+* Default %destructor or %printer with `<*>' or `<>'
+
+  Bison now recognizes two separate kinds of default %destructor's and

   %printer's:
 
     1. Place `<*>' in a %destructor/%printer symbol list to define a default
   %printer's:
 
     1. Place `<*>' in a %destructor/%printer symbol list to define a default


@@ -61,75 +182,12 @@ Changes in version 2.3a+ (????-??-??):
   See the section `Freeing Discarded Symbols' in the Bison manual for further
   details.
 
   See the section `Freeing Discarded Symbols' in the Bison manual for further
   details.
 

-* The Yacc prologue alternatives from Bison 2.3a have been rewritten as the
-  following directives:
-
-    1. %code {CODE}
-
-       Other than semantic actions, this is probably the most common place you
-       should write verbatim code for the parser implementation.  It replaces
-       the traditional Yacc prologue, `%{CODE%}', for most purposes.  Compare
-       with:
-
-         - `%{CODE%}' appearing after the first `%union {CODE}' in a grammar
-          file.  While Bison will continue to support `%{CODE%}' for backward
-          compatibility, `%code {CODE}' is cleaner as its functionality does
-          not depend on its position in the grammar file relative to any
-          `%union {CODE}'.  Specifically, `%code {CODE}' always inserts your
-          CODE into the parser code file after the usual contents of the
-          parser header file.
-         - `%after-header {CODE}', which only Bison 2.3a supported.
-
-    2. %requires {CODE}
-
-       This is the right place to write dependency code for externally exposed
-       definitions required by Bison.  Such exposed definitions are those
-       usually appearing in the parser header file.  Thus, this is the right
-       place to define types referenced in `%union {CODE}' directives, and it
-       is the right place to override Bison's default YYSTYPE and YYLTYPE
-       definitions.  Compare with:
-
-         - `%{CODE%}' appearing before the first `%union {CODE}' in a grammar
-           file.  Unlike `%{CODE%}', `%requires {CODE}' inserts your CODE both
-           into the parser code file and into the parser header file since
-           Bison's required definitions should depend on it in both places.
-         - `%start-header {CODE}', which only Bison 2.3a supported.
-
-    3. %provides {CODE}
-    
-       This is the right place to write additional definitions you would like
-       Bison to expose externally.  That is, this directive inserts your CODE
-       both into the parser header file and into the parser code file after
-       Bison's required definitions.  Compare with:
-
-         - `%end-header {CODE}', which only Bison 2.3a supported.
-
-    4. %code-top {CODE}
-
-       Occasionally it is desirable to insert code near the top of the parser
-       code file.  For example:
-
-         %code-top {
-           #define _GNU_SOURCE
-           #include <stdio.h>
-         }
-
-       Compare with:
-
-         - `%{CODE%}' appearing before the first `%union {CODE}' in a grammar
-           file.  `%code-top {CODE}' is cleaner as its functionality does not
-           depend on its position in the grammar file relative to any
-           `%union {CODE}'.
-         - `%before-header {CODE}', which only Bison 2.3a supported.
-
-  If you have multiple occurrences of any one of the above four directives,
-  Bison will concatenate the contents in the order they appear in the grammar
-  file.
-
-  The prologue alternatives are experimental.  More user feedback will help to
-  determine whether they should become permanent features.
+* %left, %right, and %nonassoc can now declare token numbers.  This is required
+  by POSIX.  However, see the end of section `Operator Precedence' in the Bison
+  manual for a caveat concerning the treatment of literal strings.

 
 

-  Also see the new section `Prologue Alternatives' in the Bison manual.
+* The nonfunctional --no-parser, -n, and %no-parser options have been
+  completely removed from Bison.

 
 Changes in version 2.3a, 2006-09-13:
 
 
 Changes in version 2.3a, 2006-09-13:
 


@@ -955,21 +1013,19 @@ End:
 -----
 
 Copyright (C) 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003,
 -----
 
 Copyright (C) 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003,

-2004, 2005, 2006 Free Software Foundation, Inc.
+2004, 2005, 2006, 2007, 2008 Free Software Foundation, Inc.

 
 This file is part of Bison, the GNU Compiler Compiler.
 
 
 This file is part of Bison, the GNU Compiler Compiler.
 

-Bison is free software; you can redistribute it and/or modify
+This program is free software: you can redistribute it and/or modify

 it under the terms of the GNU General Public License as published by
 it under the terms of the GNU General Public License as published by

-the Free Software Foundation; either version 2, or (at your option)
-any later version.
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.

 
 

-Bison is distributed in the hope that it will be useful,
+This program is distributed in the hope that it will be useful,

 but WITHOUT ANY WARRANTY; without even the implied warranty of
 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 GNU General Public License for more details.
 
 You should have received a copy of the GNU General Public License
 but WITHOUT ANY WARRANTY; without even the implied warranty of
 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 GNU General Public License for more details.
 
 You should have received a copy of the GNU General Public License

-along with autoconf; see the file COPYING.  If not, write to
-the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
-Boston, MA 02110-1301, USA.
+along with this program.  If not, see <http://www.gnu.org/licenses/>.