Bison News
----------
-Changes in version 1.49b:
+Changes in version 1.49b, 2002-08-12:
+
+* GLR parsing
+ The declaration
+ %glr-parser
+ causes Bison to produce a Generalized LR (GLR) parser, capable of handling
+ almost any context-free grammar, ambiguous or not. The new declarations
+ %dprec and %merge on grammar rules allow parse-time resolution of
+ ambiguities. Contributed by Paul Hilfinger.
* Output Directory
When not in Yacc compatibility mode, when the output file was not
user specified that one of her tokens is numbered 256, then error
will be mapped onto another number.
+* Verbose error messages
+ They no longer report `..., expecting error or...' for state where
+ error recovery is possible.
+
+* End token
+ Defaults to `$end' instead of `$'.
+
* Error recovery now conforms to documentation and to POSIX
When a Bison-generated parser encounters a syntax error, it now pops
the stack until it finds a state that allows shifting the error
* Traces
Popped tokens and nonterminals are now reported.
-* Large grammars
- Large grammars are now supported (large token numbers, large grammar
- size (= sum of the LHS and RHS lengths), large LALR tables).
+* Larger grammars
+ Larger grammars are now supported (larger token numbers, larger grammar
+ size (= sum of the LHS and RHS lengths), larger LALR tables).
+ Formerly, many of these numbers ran afoul of 16-bit limits;
+ now these limits are 32 bits on most hosts.
* Explicit initial rule
Bison used to play hacks with the initial rule, which the user does
* Useless rules, useless nonterminals
They are now reported, as a warning, with their locations.
+* Rules never reduced
+ Rules that can never be reduced because of conflicts are now
+ reported.
+
* Incorrect `Token not used'
On a grammar such as
* Token end-of-file
The token end of file may be specified by the user, in which case,
the user symbol is used in the reports, the graphs, and the verbose
- error messages instead of `$', which remains being the defaults.
+ error messages instead of `$end', which remains being the default.
For instance
%token YYEOF 0
or
* Semantic parser
This old option, which has been broken for ages, is removed.
-* New translation
+* New translations
+ Brazilian Portuguese, thanks to Alexandre Folle de Menezes.
Croatian, thanks to Denis Lackovic.
* Incorrect token definitions
bar: '0' {} '0';
This is fixed.
+
+* GNU M4 is now required when using Bison.
\f
Changes in version 1.35, 2002-03-25: