-*- outline -*-
-* 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
-%union.
-
-When implementing multiple-%union support, bare the following in mind:
-
-- when --yacc, this must be flagged as an error. Don't make it fatal
- though.
+* URGENT: Documenting C++ output
+Write a first documentation for C++ output.
-- The #line must now appear *inside* the definition of yystype.
- Something like
- {
- #line 12 "foo.y"
- int ival;
- #line 23 "foo.y"
- char *sval;
- }
+* Documentation
+Before releasing, make sure the documentation refers to the current
+`output' format.
-* Experimental report features
-Decide whether they should be enabled, or optional. For instance, on:
- input:
- exp
- | input exp
- ;
+* Error messages
+Some are really funky. For instance
- exp:
- token1 "1"
- | token2 "2"
- | token3 "3"
- ;
+ type clash (`%s' `%s') on default action
- token1: token;
- token2: token;
- token3: token;
+is really weird. Revisit them all.
-the traditional Bison reports:
- state 0
+* 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.
- $axiom -> . input $ (rule 0)
- token shift, and go to state 1
+* 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?
- 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
+* Report
- token1 -> token . (rule 6)
- token2 -> token . (rule 7)
- token3 -> token . (rule 8)
+** 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.
- "2" reduce using rule 7 (token2)
- "3" reduce using rule 8 (token3)
- $default reduce using rule 6 (token1)
+** Disabled Reductions
+See `tests/conflicts.at (Defaulted Conflicted Reduction)', and decide
+what we want to do.
-while with --trace, i.e., when enabling both the display of non-core
-item sets and the display of lookaheads, Bison now displays:
+** 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?
- state 0
+** --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.
- $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
+* Extentions
- 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
+** 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...
- state 1
+** 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
+%union.
- token1 -> token . ["1"] (rule 6)
- token2 -> token . ["2"] (rule 7)
- token3 -> token . ["3"] (rule 8)
+When implementing multiple-%union support, bare the following in mind:
- "2" reduce using rule 7 (token2)
- "3" reduce using rule 8 (token3)
- $default reduce using rule 6 (token1)
+- when --yacc, this must be flagged as an error. Don't make it fatal
+ though.
-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:
+- The #line must now appear *inside* the definition of yystype.
+ Something like
- state 0
- Core:
- $axiom -> . input $ (rule 0)
+ {
+ #line 12 "foo.y"
+ int ival;
+ #line 23 "foo.y"
+ char *sval;
+ }
- 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)
+* Unit rules
+Maybe we could expand unit rules, i.e., transform
- token shift, and go to state 1
+ exp: arith | bool;
+ arith: exp '+' exp;
+ bool: exp '&' exp;
- 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
+into
+ exp: exp '+' exp | exp '&' exp;
-> So, it seems clear that it has to be an additional option :)
+when there are no actions. This can significantly speed up some
+grammars. I can't find the papers. In particular the book `LR
+parsing: Theory and Practice' is impossible to find, but according to
+`Parsing Techniques: a Practical Guide', it includes information about
+this issue. Does anybody have it?
-Paul:
- There will be further such options in the future, so I'd make
- them all operands of the --report option. E.g., you could do
- something like this:
- --report=state --report=lookahead --report=itemset
- --report=conflict-path
+* Documentation
- where "--verbose" is equivalent to "--report=state", and where
- "--report=conflict-path" reports each path to a conflict
- state.
+** History/Bibliography
+Some history of Bison and some bibliography would be most welcome.
+Are there any Texinfo standards for bibliography?
- (As a minor point, I prefer avoiding plurals in option names.
- It's partly for brevity, and partly to avoid wearing out the
- 's' keys in our keyboards. :-)
-To implement this, see in the Fileutils the latest versions of
-argmatch and so forth.
* Coding system independence
PDP-10 ports :-) but they should probably be documented
somewhere.
-* Output directory
-Akim:
-
-| I consider this to be a bug in bison:
-|
-| /tmp % mkdir src
-| /tmp % cp ~/src/bison/tests/calc.y src
-| /tmp % mkdir build && cd build
-| /tmp/build % bison ../src/calc.y
-| /tmp/build % cd ..
-| /tmp % ls -l build src
-| build:
-| total 0
-|
-| src:
-| total 32
-| -rw-r--r-- 1 akim lrde 27553 oct 2 16:31 calc.tab.c
-| -rw-r--r-- 1 akim lrde 3335 oct 2 16:31 calc.y
-|
-|
-| Would it be safe to change this behavior to something more reasonable?
-| Do you think some people depend upon this?
-
-Jim:
-
-Is it that behavior documented?
-If so, then it's probably not reasonable to change it.
-I've Cc'd the automake list, because some of automake's
-rules use bison through $(YACC) -- though I'll bet they
-all use it in yacc-compatible mode.
-
-Pavel:
-
-Hello, Jim and others!
-
-> Is it that behavior documented?
-> If so, then it's probably not reasonable to change it.
-> I've Cc'd the automake list, because some of automake's
-> rules use bison through $(YACC) -- though I'll bet they
-> all use it in yacc-compatible mode.
-
-Yes, Automake currently used bison in Automake-compatible mode, but it
-would be fair for Automake to switch to the native mode as long as the
-processed files are distributed and "missing" emulates bison.
-
-In any case, the makefiles should specify the output file explicitly
-instead of relying on weird defaults.
-
-> | src:
-> | total 32
-> | -rw-r--r-- 1 akim lrde 27553 oct 2 16:31 calc.tab.c
-> | -rw-r--r-- 1 akim lrde 3335 oct 2 16:31 calc.y
-
-This is not _that_ ugly as it seems - with Automake you want to put
-sources where they belong - to the source directory.
-
-> | This is not _that_ ugly as it seems - with Automake you want to put
-> | sources where they belong - to the source directory.
->
-> The difference source/build you are referring to is based on Automake
-> concepts. They have no sense at all for tools such as bison or gcc
-> etc. They have input and output. I do not want them to try to grasp
-> source/build. I want them to behave uniformly: output *here*.
-
-I realize that.
-
-It's unfortunate that the native mode of Bison behaves in a less uniform
-way than the yacc mode. I agree with your point. Bison maintainters may
-want to fix it along with the documentation.
-
-
-* Unit rules
-Maybe we could expand unit rules, i.e., transform
-
- exp: arith | bool;
- arith: exp '+' exp;
- bool: exp '&' exp;
-
-into
-
- exp: exp '+' exp | exp '&' exp;
-
-when there are no actions. This can significantly speed up some
-grammars.
-
-* 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 '('
-
-* 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...
-
-* 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.
-* Memory leaks in the parser
-The same applies to the generated parsers. In particular, this is
-critical for user data: when aborting a parsing, when handling the
-error token etc., we often throw away yylval without giving a chance
-of cleaning it up to the user.
* --graph
Show reductions. []
** tests/pure-parser.at []
New tests.
-* Debugging parsers
-
-From Greg McGary:
-
-akim demaille <akim.demaille@epita.fr> writes:
-
-> With great pleasure! Nonetheless, things which are debatable
-> (or not, but just `big') should be discuss in `public': something
-> like help- or bug-bison@gnu.org is just fine. Jesse and I are there,
-> but there is also Jim and some other people.
-
-I have no idea whether it qualifies as big or controversial, so I'll
-just summarize for you. I proposed this change years ago and was
-surprised that it was met with utter indifference!
-
-This debug feature is for the programs/grammars one develops with
-bison, not for debugging bison itself. I find that the YYDEBUG
-output comes in a very inconvenient format for my purposes.
-When debugging gcc, for instance, what I want is to see a trace of
-the sequence of reductions and the line#s for the semantic actions
-so I can follow what's happening. Single-step in gdb doesn't cut it
-because to move from one semantic action to the next takes you through
-lots of internal machinery of the parser, which is uninteresting.
-
-The change I made was to the format of the debug output, so that it
-comes out in the format of C error messages, digestible by emacs
-compile mode, like so:
-
-grammar.y:1234: foo: bar(0x123456) baz(0x345678)
-
-where "foo: bar baz" is the reduction rule, whose semantic action
-appears on line 1234 of the bison grammar file grammar.y. The hex
-numbers on the rhs tokens are the parse-stack values associated with
-those tokens. Of course, yytype might be something totally
-incompatible with that representation, but for the most part, yytype
-values are single words (scalars or pointers). In the case of gcc,
-they're most often pointers to tree nodes. Come to think of it, the
-right thing to do is to make the printing of stack values be
-user-definable. It would also be useful to include the filename &
-line# of the file being parsed, but the main filename & line# should
-continue to be that of grammar.y
-
-Anyway, this feature has saved my life on numerous occasions. The way
-I customarily use it is to first run bison with the traces on, isolate
-the sequence of reductions that interests me, put those traces in a
-buffer and force it into compile-mode, then visit each of those lines
-in the grammar and set breakpoints with C-x SPACE. Then, I can run
-again under the control of gdb and stop at each semantic action.
-With the hex addresses of tree nodes, I can inspect the values
-associated with any rhs token.
-
-You like?
-
* input synclines
Some users create their foo.y files, and equip them with #line. Bison
should recognize these, and preserve them.
See if we can integrate backtracking in Bison. Contact the BTYacc
maintainers.
-* Automaton report
-Display more clearly the lookaheads for each item.
+** 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.
-* RR conflicts
-See if we can use precedence between rules to solve RR conflicts. See
-what POSIX says.
* 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.
-* Parsing grammars
-Rewrite the reader in Flex/Bison. There will be delicate parts, in
-particular, expect the scanner to be hard to write. Many interesting
-features cannot be implemented without such a new reader.
-
-* Presentation of the report file
-From: "Baum, Nathan I" <s0009525@chelt.ac.uk>
-Subject: Token Alias Bug
-To: "'bug-bison@gnu.org'" <bug-bison@gnu.org>
-
-I've also noticed something, that whilst not *wrong*, is inconvienient: I
-use the verbose mode to help find the causes of unresolved shift/reduce
-conflicts. However, this mode insists on starting the .output file with a
-list of *resolved* conflicts, something I find quite useless. Might it be
-possible to define a -v mode, and a -vv mode -- Where the -vv mode shows
-everything, but the -v mode only tells you what you need for examining
-conflicts? (Or, perhaps, a "*** This state has N conflicts ***" marker above
-each state with conflicts.)
+** 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:
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
Note: Robert Anisko handles this. He knows how to do it.
-* Documenting C++ output
-Write a first documentation for C++ output.
* Warnings
It would be nice to have warning support. See how Autoconf handles
thought about it, and know many of the components that can be used to
implement it.
+
* Pre and post actions.
From: Florian Krohm <florian@edamail.fishkill.ibm.com>
Subject: YYACT_EPILOGUE
I was wondering what you think about adding YYACT_PROLOGUE/EPILOGUE
to bison. If you're interested, I'll work on a patch.
+* Move to Graphviz
+Well, VCG seems really dead. Move to Graphviz instead. Also, equip
+the parser with a means to create the (visual) parse tree.
+
-----
Copyright (C) 2001, 2002 Free Software Foundation, Inc.
-This file is part of GNU Autoconf.
+This file is part of GNU Bison.
-GNU Autoconf is free software; you can redistribute it and/or modify
+GNU Bison is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2, or (at your option)
any later version.
-GNU Autoconf is distributed in the hope that it will be useful,
+GNU Bison is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
-along with autoconf; see the file COPYING. If not, write to
+along with Bison; see the file COPYING. If not, write to
the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA.
projects / bison.git / blobdiff