* doc/yacc.1.in: New.

[bison.git] / NEWS

diff --git a/NEWS b/NEWS
index 0e4061aab57d2f191120d123592f063f89a338eb..ad7903cc6e7d2e7ab9e076ea91c5bebe46ec8717 100644 (file)
--- a/NEWS
+++ b/NEWS
@@ -3,17 +3,30 @@ Bison News
 
 Changes in version 2.3a+ (????-??-??):
 
-* Previously, Bison sometimes generated parser tables with states that were
-  unreachable due to conflicts in predecessor states.  Bison now:
+* The quotes around NAME that used to be required in the following directive
+  are now deprecated:
 
-    1. Removes unreachable states.
+    %define NAME "VALUE"
 
-    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.
+* The directive `%pure-parser' is now deprecated in favor of:
 
-    3. For any rule used only in such states, Bison now reports the rule as
-       "never reduced because of conflicts".
+    %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.
@@ -28,6 +41,43 @@ Changes in version 2.3a+ (????-??-??):
 
     %defines "parser.h"
 
+* When reporting useless rules and nonterminals, Bison now employs the term
+  "useless in grammar" instead of "useless" and employs the term "useless in
+  parser" instead of "never reduced".
+
+* 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.
+
 * The `=' that used to be required in the following directives is now
   deprecated:
 
@@ -35,12 +85,9 @@ Changes in version 2.3a+ (????-??-??):
     %name-prefix "c_"
     %output "parser.c"
 
-* The quotes around NAME that used to be required in the following directive
-  are now deprecated:
-
-    %define NAME "VALUE"
+* An Alternative to `%{...%}' -- `%code QUALIFIER {CODE}'
 
-* Bison 2.3a provided a new set of directives as a more flexible alternative to
+  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
@@ -79,7 +126,9 @@ Changes in version 2.3a+ (????-??-??):
   To enable these warnings, specify the flag `--warnings=midrule-values' or
   `-W', which is a synonym for `--warnings=all'.
 
-* 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