TODO update

[Akim Demaille]

Index: TODO
===================================================================
RCS file: /cvsroot/bison/bison/TODO,v
retrieving revision 1.72
diff -u -u -r1.72 TODO
--- TODO 30 Jun 2002 17:32:47 -0000 1.72
+++ TODO 9 Jul 2002 10:35:44 -0000
@@ -3,52 +3,83 @@
 * URGENT: Documenting C++ output
 Write a first documentation for C++ output.
 
-* Report and GLR
-How would Paul like to display the conflicted actions?  In particular,
-what when two reductions are possible on a given lookahead, but one is
-part of $default.  Should we make the two reductions explicit, or just
-keep $default?  See the following point.
 
-* Report and Disabled Reductions
-See `tests/conflicts.at (Defaulted Conflicted Reduction)', and decide
-what we want to do.
+* Error messages
+Some are really funky.  For instance
+
+       type clash (`%s' `%s') on default action
+
+is really weird.  Revisit them all.
+
+* Stupid error messages
+An example shows it easily:
+
+src/bison/tests % ./testsuite -k calc,location,error-verbose -l
+GNU Bison 1.49a test suite test groups:
+
+ NUM: FILENAME:LINE      TEST-GROUP-NAME
+      KEYWORDS
+
+  51: calc.at:440        Calculator --locations --yyerror-verbose
+  52: calc.at:442        Calculator --defines --locations --name-prefix=calc 
--verbose --yacc --yyerror-verbose
+  54: calc.at:445        Calculator --debug --defines --locations 
--name-prefix=calc --verbose --yacc --yyerror-verbose
+src/bison/tests % ./testsuite 51 -d
+## --------------------------- ##
+## GNU Bison 1.49a test suite. ##
+## --------------------------- ##
+ 51: calc.at:440       ok
+## ---------------------------- ##
+## All 1 tests were successful. ##
+## ---------------------------- ##
+src/bison/tests % cd ./testsuite.dir/51
+tests/testsuite.dir/51 % echo "()" | ./calc
+1.2-1.3: parse error, unexpected ')', expecting error or "number" or '-' or '('
+
+
+* read_pipe.c
+This is not portable to DOS for instance.  Implement a more portable
+scheme.  Sources of inspiration include GNU diff, and Free Recode.
+
 
 * value_components_used
 Was defined but not used: where was it coming from?  It can't be to
 check if %union is used, since the user is free to $<foo>n on her
 union, doesn't she?
 
-* yyerror, yyprint interface
-It should be improved, in particular when using Bison features such as
-locations, and YYPARSE_PARAMS.  For the time being, it is recommended
-to #define yyerror and yyprint to steal internal variables...
 
-* documentation
-Explain $axiom (and maybe change its name: BTYacc names it `goal',
-byacc `$accept' probably based on AT&T Yacc, Meta `Start'...).
-Complete the glossary (item, axiom, ?).  Should we also rename `$'?
-BYacc uses `$end'.  `$eof' is attracting, but after all we may be
-parsing a string, a stream etc.
+* Report
 
-* Error messages
-Some are really funky.  For instance
-
-       type clash (`%s' `%s') on default action
+**  GLR
+How would Paul like to display the conflicted actions?  In particular,
+what when two reductions are possible on a given lookahead, but one is
+part of $default.  Should we make the two reductions explicit, or just
+keep $default?  See the following point.
 
-is really weird.  Revisit them all.
+** Disabled Reductions
+See `tests/conflicts.at (Defaulted Conflicted Reduction)', and decide
+what we want to do.
 
-* Report documentation
+** Documentation
 Extend with error productions.  The hard part will probably be finding
 the right rule so that a single state does not exhibit too many yet
 undocumented ``features''.  Maybe an empty action ought to be
 presented too.  Shall we try to make a single grammar with all these
 features, or should we have several very small grammars?
 
-* Documentation
-Some history of Bison and some bibliography would be most welcome.
-Are there any Texinfo standards for bibliography?
+** --report=conflict-path
+Provide better assistance for understanding the conflicts by providing
+a sample text exhibiting the (LALR) ambiguity.  See the paper from
+DeRemer and Penello: they already provide the algorithm.
+
 
-* Several %unions
+* Extentions
+
+** yyerror, yysymprint interface
+It should be improved, in particular when using Bison features such as
+locations, and YYPARSE_PARAMS.  For the time being, it is recommended
+to #define yyerror and yyprint to steal internal variables...
+
+** Several %unions
 I think this is a pleasant (but useless currently) feature, but in the
 future, I want a means to %include other bits of grammars, and _then_
 it will be important for the various bits to define their needs in
@@ -69,24 +100,6 @@
          char *sval;
        }
 
-* --report=conflict-path
-Provide better assistance for understanding the conflicts by providing
-a sample text exhibiting the (LALR) ambiguity.  See the paper from
-DeRemer and Penello: they already provide the algorithm.
-
-* Coding system independence
-Paul notes:
-
-       Currently Bison assumes 8-bit bytes (i.e. that UCHAR_MAX is
-       255).  It also assumes that the 8-bit character encoding is
-       the same for the invocation of 'bison' as it is for the
-       invocation of 'cc', but this is not necessarily true when
-       people run bison on an ASCII host and then use cc on an EBCDIC
-       host.  I don't think these topics are worth our time
-       addressing (unless we find a gung-ho volunteer for EBCDIC or
-       PDP-10 ports :-) but they should probably be documented
-       somewhere.
-
 * Unit rules
 Maybe we could expand unit rules, i.e., transform
 
@@ -104,37 +117,38 @@
 `Parsing Techniques: a Practical Guide', it includes information about
 this issue.  Does anybody have it?
 
-* Stupid error messages
-An example shows it easily:
 
-src/bison/tests % ./testsuite -k calc,location,error-verbose -l
-GNU Bison 1.49a test suite test groups:
 
- NUM: FILENAME:LINE      TEST-GROUP-NAME
-      KEYWORDS
+* Documentation
 
-  51: calc.at:440        Calculator --locations --yyerror-verbose
-  52: calc.at:442        Calculator --defines --locations --name-prefix=calc 
--verbose --yacc --yyerror-verbose
-  54: calc.at:445        Calculator --debug --defines --locations 
--name-prefix=calc --verbose --yacc --yyerror-verbose
-src/bison/tests % ./testsuite 51 -d
-## --------------------------- ##
-## GNU Bison 1.49a test suite. ##
-## --------------------------- ##
- 51: calc.at:440       ok
-## ---------------------------- ##
-## All 1 tests were successful. ##
-## ---------------------------- ##
-src/bison/tests % cd ./testsuite.dir/51
-tests/testsuite.dir/51 % echo "()" | ./calc
-1.2-1.3: parse error, unexpected ')', expecting error or "number" or '-' or '('
+** Vocabulary
+Explain $axiom (and maybe change its name: BTYacc names it `goal',
+byacc `$accept' probably based on AT&T Yacc, Meta `Start'...).
+Complete the glossary (item, axiom, ?).  Should we also rename `$'?
+BYacc uses `$end'.  `$eof' is attracting, but after all we may be
+parsing a string, a stream etc.
+
+** History/Bibliography
+Some history of Bison and some bibliography would be most welcome.
+Are there any Texinfo standards for bibliography?
+
+
+
+
+* Coding system independence
+Paul notes:
+
+       Currently Bison assumes 8-bit bytes (i.e. that UCHAR_MAX is
+       255).  It also assumes that the 8-bit character encoding is
+       the same for the invocation of 'bison' as it is for the
+       invocation of 'cc', but this is not necessarily true when
+       people run bison on an ASCII host and then use cc on an EBCDIC
+       host.  I don't think these topics are worth our time
+       addressing (unless we find a gung-ho volunteer for EBCDIC or
+       PDP-10 ports :-) but they should probably be documented
+       somewhere.
 
-* read_pipe.c
-This is not portable to DOS for instance.  Implement a more portable
-scheme.  Sources of inspiration include GNU diff, and Free Recode.
 
-* Memory leaks in the generator
-A round of memory leak clean ups would be most welcome.  Dmalloc,
-Checker GCC, Electric Fence, or Valgrind: you chose your tool.
 
 * --graph
 Show reductions.       []
@@ -178,18 +192,47 @@
 See if we can integrate backtracking in Bison.  Contact the BTYacc
 maintainers.
 
-* RR conflicts
-See if we can use precedence between rules to solve RR conflicts.  See
-what POSIX says.
+** Keeping the conflicted actions
+First, analyze the differences between byacc and btyacc (I'm referring
+to the executables).  Find where the conflicts are preserved.
+
+** Compare with the GLR tables
+See how isomorphic the way BTYacc and the way the GLR adjustements in
+Bison are compatible.  *As much as possible* one should try to use the
+same implementation in the Bison executables.  I insist: it should be
+very feasible to use the very same conflict tables.
+
+** Adjust the skeletons
+Import the skeletons for C and C++.
+
+** Improve the skeletons
+Have them support yysymprint, yydestruct and so forth.
+
 
 * Precedence
+
+** Partial order
 It is unfortunate that there is a total order for precedence.  It
 makes it impossible to have modular precedence information.  We should
-move to partial orders.
+move to partial orders (sounds like series/parallel orders to me).
 
 This will be possible with a Bison parser for the grammar, as it will
 make it much easier to extend the grammar.
 
+** Correlation b/w precedence and associativity
+Also, I fail to understand why we have to assign the same
+associativity to operators with the same precedence.  For instance,
+why can't I decide that the precedence of * and / is the same, but the
+latter is nonassoc?
+
+If there is really no profound motivation, we should find a new syntax
+to allow specifying this.
+
+** RR conflicts
+See if we can use precedence between rules to solve RR conflicts.  See
+what POSIX says.
+
+
 * $undefined
 From Hans:
 - If the Bison generated parser experiences an undefined number in the
@@ -198,6 +241,7 @@
 
 Suggest: Change the name $undefined to undefined; looks better in outputs.
 
+
 * Default Action
 From Hans:
 - For use with my C++ parser, I transported the "switch (yyn)" statement
@@ -214,6 +258,7 @@
 
 Note: Robert Anisko handles this.  He knows how to do it.
 
+
 * Warnings
 It would be nice to have warning support.  See how Autoconf handles
 them, it is fairly well described there.  It would be very nice to
@@ -223,6 +268,7 @@
 Don't work on this without first announcing you do, as I already have
 thought about it, and know many of the components that can be used to
 implement it.
+
 
 * Pre and post actions.
 From: Florian Krohm <address@hidden>