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
+ specified, runnning `bison foo/bar.y' created `foo/bar.c'. It
+ now creates `bar.c'.
* Undefined token
The undefined token was systematically mapped to 2 which prevented
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: