Version 1.3
------------------------------
12/10/02: jmdyck
          Various minor adjustments to the code that Dave checked in today.
          Updated test/yacc_{inf,unused}.exp to reflect today's changes.

12/10/02: beazley
          Incorporated a variety of minor bug fixes to empty production
          handling and infinite recursion checking.  Contributed by
          Michael Dyck.

12/10/02: beazley
          Removed bogus recover() method call in yacc.restart()

Version 1.2
------------------------------
11/27/02: beazley
          Lexer and parser objects are now available as an attribute
          of tokens and slices respectively. For example:
 
             def t_NUMBER(t):
                 r'\d+'
                 print t.lexer

             def p_expr_plus(t):
                 'expr: expr PLUS expr'
                 print t.lexer
                 print t.parser

          This can be used for state management (if needed).
 
10/31/02: beazley
          Modified yacc.py to work with Python optimize mode.  To make
          this work, you need to use

              yacc.yacc(optimize=1)

          Furthermore, you need to first run Python in normal mode
          to generate the necessary parsetab.py files.  After that,
          you can use python -O or python -OO.  

          Note: optimized mode turns off a lot of error checking.
          Only use when you are sure that your grammar is working.
          Make sure parsetab.py is up to date!

10/30/02: beazley
          Added cloning of Lexer objects.   For example:

              import copy
              l = lex.lex()
              lc = copy.copy(l)

              l.input("Some text")
              lc.input("Some other text")
              ...

          This might be useful if the same "lexer" is meant to
          be used in different contexts---or if multiple lexers
          are running concurrently.
                
10/30/02: beazley
          Fixed subtle bug with first set computation and empty productions.
          Patch submitted by Michael Dyck.

10/30/02: beazley
          Fixed error messages to use "filename:line: message" instead
          of "filename:line. message".  This makes error reporting more
          friendly to emacs. Patch submitted by François Pinard.

10/30/02: beazley
          Improvements to parser.out file.  Terminals and nonterminals
          are sorted instead of being printed in random order.
          Patch submitted by François Pinard.

10/30/02: beazley
          Improvements to parser.out file output.  Rules are now printed
          in a way that's easier to understand.  Contributed by Russ Cox.

10/30/02: beazley
          Added 'nonassoc' associativity support.    This can be used
          to disable the chaining of operators like a < b < c.
          To use, simply specify 'nonassoc' in the precedence table

          precedence = (
            ('nonassoc', 'LESSTHAN', 'GREATERTHAN'),  # Nonassociative operators
            ('left', 'PLUS', 'MINUS'),
            ('left', 'TIMES', 'DIVIDE'),
            ('right', 'UMINUS'),            # Unary minus operator
          )

          Patch contributed by Russ Cox.

10/30/02: beazley
          Modified the lexer to provide optional support for Python -O and -OO
          modes.  To make this work, Python *first* needs to be run in
          unoptimized mode.  This reads the lexing information and creates a
          file "lextab.py".  Then, run lex like this:

                   # module foo.py
                   ...
                   ...
                   lex.lex(optimize=1)

          Once the lextab file has been created, subsequent calls to
          lex.lex() will read data from the lextab file instead of using 
          introspection.   In optimized mode (-O, -OO) everything should
          work normally despite the loss of doc strings.

          To change the name of the file 'lextab.py' use the following:

                  lex.lex(lextab="footab")

          (this creates a file footab.py)
         

Version 1.1   October 25, 2001
------------------------------

10/25/01: beazley
          Modified the table generator to produce much more compact data.
          This should greatly reduce the size of the parsetab.py[c] file.
          Caveat: the tables still need to be constructed so a little more
          work is done in parsetab on import. 

10/25/01: beazley
          There may be a possible bug in the cycle detector that reports errors
          about infinite recursion.   I'm having a little trouble tracking it
          down, but if you get this problem, you can disable the cycle
          detector as follows:

                 yacc.yacc(check_recursion = 0)

10/25/01: beazley
          Fixed a bug in lex.py that sometimes caused illegal characters to be
          reported incorrectly.  Reported by Sverre Jørgensen.

7/8/01  : beazley
          Added a reference to the underlying lexer object when tokens are handled by
          functions.   The lexer is available as the 'lexer' attribute.   This
          was added to provide better lexing support for languages such as Fortran
          where certain types of tokens can't be conveniently expressed as regular 
          expressions (and where the tokenizing function may want to perform a 
          little backtracking).  Suggested by Pearu Peterson.

6/20/01 : beazley
          Modified yacc() function so that an optional starting symbol can be specified.
          For example:
            
                 yacc.yacc(start="statement")

          Normally yacc always treats the first production rule as the starting symbol.
          However, if you are debugging your grammar it may be useful to specify
          an alternative starting symbol.  Idea suggested by Rich Salz.
                      
Version 1.0  June 18, 2001
--------------------------
Initial public offering

