New experimental feature: display the lookaheads in the report and

[bison.git] / TODO

diff --git a/TODO b/TODO
index bc474d21aee7183e7eeada910dd8e17485e51910..4780351fa3f0e35a78e760baf3b351d069a7387a 100644 (file)
--- a/TODO
+++ b/TODO
@@ -21,6 +21,110 @@ When implementing multiple-%union support, bare the following in mind:
          char *sval;
        }
 
+* Experimental report features
+Decide whether they should be enabled, or optional.  For instance, on:
+
+       input:
+         exp
+       | input exp
+       ;
+
+       exp:
+         token1 "1"
+       | token2 "2"
+       | token3 "3"
+       ;
+
+       token1: token;
+       token2: token;
+       token3: token;
+
+the traditional Bison reports:
+
+       state 0
+
+           $axiom  ->  . input $   (rule 0)
+
+           token       shift, and go to state 1
+
+           input       go to state 2
+           exp         go to state 3
+           token1      go to state 4
+           token2      go to state 5
+           token3      go to state 6
+
+       state 1
+
+           token1  ->  token .   (rule 6)
+           token2  ->  token .   (rule 7)
+           token3  ->  token .   (rule 8)
+
+           "2"         reduce using rule 7 (token2)
+           "3"         reduce using rule 8 (token3)
+           $default    reduce using rule 6 (token1)
+
+while with --trace, i.e., when enabling both the display of non-core
+item sets and the display of lookaheads, Bison now displays:
+
+       state 0
+
+           $axiom  ->  . input $   (rule 0)
+           input  ->  . exp   (rule 1)
+           input  ->  . input exp   (rule 2)
+           exp  ->  . token1 "1"   (rule 3)
+           exp  ->  . token2 "2"   (rule 4)
+           exp  ->  . token3 "3"   (rule 5)
+           token1  ->  . token   (rule 6)
+           token2  ->  . token   (rule 7)
+           token3  ->  . token   (rule 8)
+
+           token       shift, and go to state 1
+
+           input       go to state 2
+           exp         go to state 3
+           token1      go to state 4
+           token2      go to state 5
+           token3      go to state 6
+
+       state 1
+
+           token1  ->  token .  ["1"]   (rule 6)
+           token2  ->  token .  ["2"]   (rule 7)
+           token3  ->  token .  ["3"]   (rule 8)
+
+           "2"         reduce using rule 7 (token2)
+           "3"         reduce using rule 8 (token3)
+           $default    reduce using rule 6 (token1)
+
+so decide whether this should be an option, or always enabled.  I'm in
+favor of making it the default, but maybe we should tune the output to
+distinguish core item sets from non core:
+
+       state 0
+           Core:
+           $axiom  ->  . input $   (rule 0)
+
+           Derived:
+           input  ->  . exp   (rule 1)
+           input  ->  . input exp   (rule 2)
+           exp  ->  . token1 "1"   (rule 3)
+           exp  ->  . token2 "2"   (rule 4)
+           exp  ->  . token3 "3"   (rule 5)
+           token1  ->  . token   (rule 6)
+           token2  ->  . token   (rule 7)
+           token3  ->  . token   (rule 8)
+
+           token       shift, and go to state 1
+
+           input       go to state 2
+           exp         go to state 3
+           token1      go to state 4
+           token2      go to state 5
+           token3      go to state 6
+
+
+Note that the same questions applies to --graph.
+
 * Coding system independence
 Paul notes: