Fix documentation problems reported by Tim Josling at

[bison.git] / NEWS

diff --git a/NEWS b/NEWS
index 41eb292ca33b80f02a6f293b2f72fc1f4f0e38dd..1458cb2d3e06cf57bfca7276afedee34f2eebcbd 100644 (file)
--- a/NEWS
+++ b/NEWS
@@ -3,6 +3,31 @@ Bison News
 
 Changes in version 2.3a+ (????-??-??):
 
 
 Changes in version 2.3a+ (????-??-??):
 

+* 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 -g and --graph options now output graphs in Graphviz DOT format,
   not VCG format.
 
 * The -g and --graph options now output graphs in Graphviz DOT format,
   not VCG format.
 


@@ -16,26 +41,68 @@ Changes in version 2.3a+ (????-??-??):
 
     %defines "parser.h"
 
 
     %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 flag 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"
 

-* Bison 2.3a provided a new set of directives as a more flexible alternative to
+* 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:
 
   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}'
+    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 `Appendix A Bison Symbols' in the Bison manual for a
-  summary of the new functionality.  See the new section `Prologue
+  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.
 
   Alternatives' for a detailed discussion including the advantages of %code
   over the traditional Yacc prologues.
 


@@ -62,7 +129,9 @@ Changes in version 2.3a+ (????-??-??):
   To enable these warnings, specify the flag `--warnings=midrule-values' or
   `-W', which is a synonym for `--warnings=all'.
 
   To enable these warnings, specify the flag `--warnings=midrule-values' or
   `-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


@@ -85,6 +154,13 @@ 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.
 

+* %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.
+
+* The nonfunctional --no-parser, -n, and %no-parser options have been
+  completely removed from Bison.
+

 Changes in version 2.3a, 2006-09-13:
 
 * Instead of %union, you can define and use your own union type
 Changes in version 2.3a, 2006-09-13:
 
 * Instead of %union, you can define and use your own union type


@@ -909,21 +985,19 @@ 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/>.