Added optional support for defaulted states

1 files changed, 29 insertions, 0 deletions

diff --git a/CHANGES b/CHANGES
index ec6c71a..54ffe3b 100644
--- a/CHANGES
+++ b/CHANGES
@@ -1,5 +1,34 @@
 Version 3.5
 ---------------------
+04/21/15: beazley
+          Added optional support for defaulted_states in the parser.
+          A defaulted_state is a state where the only legal action is
+          a reduction of a single grammar rule across all valid input
+          tokens.  For such states, the rule is reduced and the
+          reading of the next lookahead token is delayed until it is
+          actually needed at a later point in time.  
+
+	  This delay in consuming the next lookahead token is a potentially
+	  important feature in advanced parsing applications that require tight
+	  interaction between the lexer and the parser.  For example, a grammar
+	  rule change modify the lexer state upon reduction and have such changes
+	  take effect before the next input token is read.
+
+	  One potential danger of defaulted_states is that syntax errors might
+	  be deferred to a a later point of processing than where they were detected
+	  in the past.   Thus, it's possible that your error handling could change
+          slightly over previous versions of PLY.
+
+	  In order to enable defaulted_state support. You need to activate it
+	  explicitly.  For example:
+
+              parser = yacc.yacc()
+              parser.use_defaulted_states()
+
+04/21/15: beazley
+          Fixed debug logging in the parser.  It wasn't properly reporting goto states
+          on grammar rule reductions.
+
 04/20/15: beazley
           Added actions to be defined to character literals (Issue #32).  For example: