X-Git-Url: https://git.saurik.com/bison.git/blobdiff_plain/271efced6772d333b524cf6227ebf2ade1b7ecac..deef2a0a4d97b580fe45a02da328b94ce32538b1:/TODO

diff --git a/TODO b/TODO
index 30abb3c4..ae0ddb66 100644
--- a/TODO
+++ b/TODO
@@ -1,150 +1,118 @@
 -*- outline -*-
 
-* URGENT: Documenting C++ output
-Write a first documentation for C++ output.
+* Header guards
 
-* 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?
+From Franc,ois: should we keep the directory part in the CPP guard?
 
-* 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, ?).
+* Yacc.c: CPP Macros
 
-* Error messages
-Some are really funky.  For instance
+Do some people use YYPURE, YYLSP_NEEDED like we do in the test suite?
+They should not: it is not documented.  But if they need to, let's
+find something clean (not like YYLSP_NEEDED...).
 
-	type clash (`%s' `%s') on default action
 
-is really weird.  Revisit them all.
-
-* Report documentation
-Extend with error.  The hard part will probably be finding the right
-rule so that a single state does not exhibit to 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?
+* Installation
 
 * Documentation
-Some history of Bison and some bibliography would be most welcome.
-Are there any Texinfo standards for bibliography?
+Before releasing, make sure the documentation ("Understanding your
+parser") refers to the current `output' format.
 
-* 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.
+* lalr1.cc
+** I18n
+Catch up with yacc.c.
 
-When implementing multiple-%union support, bare the following in mind:
+* Report
 
-- when --yacc, this must be flagged as an error.  Don't make it fatal
-  though.
+**  GLR
+How would Paul like to display the conflicted actions?  In particular,
+what when two reductions are possible on a given lookahead token, but one is
+part of $default.  Should we make the two reductions explicit, or just
+keep $default?  See the following point.
 
-- The #line must now appear *inside* the definition of yystype.
-  Something like
+** Disabled Reductions
+See `tests/conflicts.at (Defaulted Conflicted Reduction)', and decide
+what we want to do.
 
-	{
-	#line 12 "foo.y"
-	  int ival;
-	#line 23 "foo.y"
-	  char *sval;
-	}
+** 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?
 
-* --report=conflict-path
+** --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:
+** Statically check for potential ambiguities in GLR grammars.  See
+<http://www.i3s.unice.fr/~schmitz/papers.html#expamb> for an approach.
 
-	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.
 
-* 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.
+* Extensions
+
+** Labeling the symbols
+Have a look at the Lemon parser generator: instead of $1, $2 etc. they
+can name the values.  This is much more pleasant.  For instance:
+
+       exp (res): exp (a) '+' exp (b) { $res = $a + $b; };
+
+I love this.  I have been bitten too often by the removal of the
+symbol, and forgetting to shift all the $n to $n-1.  If you are
+unlucky, it compiles...
+
+But instead of using $a etc., we can use regular variables.  And
+instead of using (), I propose to use `:' (again).  Paul suggests
+supporting `->' in addition to `:' to separate LHS and RHS. In other
+words:
 
+       r:exp -> a:exp '+' b:exp { r = a + b; };
+
+That requires an significant improvement of the grammar parser.  Using
+GLR would be nice.  It also requires that Bison know the type of the
+symbols (which will be useful for %include anyway).  So we have some
+time before...
+
+Note that there remains the problem of locations: `@r'?
+
+
+** $-1
+We should find a means to provide an access to values deep in the
+stack.  For instance, instead of
+
+	baz: qux { $$ = $<foo>-1 + $<bar>0 + $1; }
+
+we should be able to have:
+
+  foo($foo) bar($bar) baz($bar): qux($qux) { $baz = $foo + $bar + $qux; }
+
+Or something like this.
+
+** %if and the like
+It should be possible to have %if/%else/%endif.  The implementation is
+not clear: should it be lexical or syntactic.  Vadim Maslow thinks it
+must be in the scanner: we must not parse what is in a switched off
+part of %if.  Akim Demaille thinks it should be in the parser, so as
+to avoid falling into another CPP mistake.
+
+** -D, --define-muscle NAME=VALUE
+To define muscles via cli.  Or maybe support directly NAME=VALUE?
+
+** XML Output
+There are couple of available extensions of Bison targeting some XML
+output.  Some day we should consider including them.  One issue is
+that they seem to be quite orthogonal to the parsing technique, and
+seem to depend mostly on the possibility to have some code triggered
+for each reduction.  As a matter of fact, such hooks could also be
+used to generate the yydebug traces.  Some generic scheme probably
+exists in there.
+
+XML output for GNU Bison and gcc
+   http://www.cs.may.ie/~jpower/Research/bisonXML/
+
+XML output for GNU Bison
+   http://yaxx.sourceforge.net/
 
 * Unit rules
 Maybe we could expand unit rules, i.e., transform
@@ -163,144 +131,87 @@ 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?
 
-* 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.
-
-* 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.
+
+
+* Documentation
+
+** History/Bibliography
+Some history of Bison and some bibliography would be most welcome.
+Are there any Texinfo standards for bibliography?
+
+
+
+* Java, Fortran, etc.
+
+
+* 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.
+
+	More importantly, Bison does not currently allow NUL bytes in
+	tokens, either via escapes (e.g., "x\0y") or via a NUL byte in
+	the source code.  This should get fixed.
 
 * --graph
-Show reductions.	[]
+Show reductions.
 
 * Broken options ?
-** %no-lines		[ok]
-** %no-parser		[]
-** %pure-parser		[]
-** %token-table		[]
-** Options which could use parse_dquoted_param ().
-Maybe transfered in lex.c.
-*** %skeleton		[ok]
-*** %output		[]
-*** %file-prefix	[]
-*** %name-prefix	[]
-
-** Skeleton strategy.	[]
-Must we keep %no-parser?
-	     %token-table?
-*** New skeletons.	[]
-
-* src/print_graph.c
-Find the best graph parameters.	[]
-
-* doc/bison.texinfo
-** Update
-informations about ERROR_VERBOSE.	[]
-** Add explainations about
-skeleton muscles.	[]
-%skeleton.		[]
-
-* testsuite
-** 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.
+** %token-table
+** Skeleton strategy
+Must we keep %token-table?
 
 * BTYacc
-See if we can integrate backtracking in Bison.  Contact the BTYacc
-maintainers.
+See if we can integrate backtracking in Bison.  Charles-Henri de
+Boysson <de-boy_c@epita.fr> has been working on this, but never gave
+the results.
+
+Vadim Maslow, the maintainer of BTYacc was once contacted.  Adjusting
+the Bison grammar parser will be needed to support some extra BTYacc
+features.  This is less urgent.
+
+** 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 adjustments 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++.
 
-* 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).
+
+** 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.
 
-This will be possible with a Bison parser for the grammar, as it will
-make it much easier to extend the grammar.
 
 * $undefined
 From Hans:
@@ -310,6 +221,7 @@ addition to the $undefined value.
 
 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
@@ -324,18 +236,6 @@ $<type_name>$ = $<type_name>1. I therefore think that one should implement
 a Bison option where every typed default rule is explicitly written out
 (same typed ruled can of course be grouped together).
 
-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
-implement this in such a way that other programs could use
-lib/warnings.[ch].
-
-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 <florian@edamail.fishkill.ibm.com>
 Subject: YYACT_EPILOGUE
@@ -364,27 +264,25 @@ at the proper place to bison.simple. Ditto for YYACT_PROLOGUE.
 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.
+* Better graphics
+Equip the parser with a means to create the (visual) parse tree.
 
 -----
 
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+Inc.
 
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