mirror of
git://code.qt.io/qt/qt5.git
synced 2026-05-04 02:07:48 +08:00
Long live the qt5 Qt repository
This commit is contained in:
Qt by Nokia
309
gnuwin32/contrib/bison/2.4.1/bison-2.4.1-src/TODO
Normal file
309
gnuwin32/contrib/bison/2.4.1/bison-2.4.1-src/TODO
Normal file
@@ -0,0 +1,309 @@
|
||||
-*- outline -*-
|
||||
|
||||
* Header guards
|
||||
|
||||
From Franc,ois: should we keep the directory part in the CPP guard?
|
||||
|
||||
|
||||
* Yacc.c: CPP Macros
|
||||
|
||||
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...).
|
||||
|
||||
|
||||
* Installation
|
||||
|
||||
* Documentation
|
||||
Before releasing, make sure the documentation ("Understanding your
|
||||
parser") refers to the current `output' format.
|
||||
|
||||
* lalr1.cc
|
||||
** vector
|
||||
Move to using vector, drop stack.hh.
|
||||
|
||||
** I18n
|
||||
Catch up with yacc.c.
|
||||
|
||||
* Report
|
||||
|
||||
** 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.
|
||||
|
||||
** Disabled Reductions
|
||||
See `tests/conflicts.at (Defaulted Conflicted Reduction)', and decide
|
||||
what we want to do.
|
||||
|
||||
** 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
|
||||
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.
|
||||
|
||||
** Statically check for potential ambiguities in GLR grammars. See
|
||||
<http://www.i3s.unice.fr/~schmitz/papers.html#expamb> for an approach.
|
||||
|
||||
|
||||
* 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
|
||||
|
||||
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. 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?
|
||||
|
||||
|
||||
|
||||
* 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.
|
||||
|
||||
* Broken options ?
|
||||
** %token-table
|
||||
** Skeleton strategy
|
||||
Must we keep %token-table?
|
||||
|
||||
* src/print_graph.c
|
||||
Find the best graph parameters.
|
||||
|
||||
* BTYacc
|
||||
See if we can integrate backtracking in Bison. Charles-Henri de
|
||||
Boysson <de-boy_c@epita.fr> is working on this, and already has some
|
||||
results. Vadim Maslow, the maintainer of BTYacc was contacted, and we
|
||||
stay in touch with him. 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++.
|
||||
|
||||
** 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 (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.
|
||||
|
||||
|
||||
* $undefined
|
||||
From Hans:
|
||||
- If the Bison generated parser experiences an undefined number in the
|
||||
character range, that character is written out in diagnostic messages, an
|
||||
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
|
||||
that Bison writes to the bison.simple skeleton file. This way, I can remove
|
||||
the current default rule $$ = $1 implementation, which causes a double
|
||||
assignment to $$ which may not be OK under C++, replacing it with a
|
||||
"default:" part within the switch statement.
|
||||
|
||||
Note that the default rule $$ = $1, when typed, is perfectly OK under C,
|
||||
but in the C++ implementation I made, this rule is different from
|
||||
$<type_name>$ = $<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
|
||||
To: bug-bison@gnu.org
|
||||
X-Sent: 1 week, 4 days, 14 hours, 38 minutes, 11 seconds ago
|
||||
|
||||
The other day I had the need for explicitly building the parse tree. I
|
||||
used %locations for that and defined YYLLOC_DEFAULT to call a function
|
||||
that returns the tree node for the production. Easy. But I also needed
|
||||
to assign the S-attribute to the tree node. That cannot be done in
|
||||
YYLLOC_DEFAULT, because it is invoked before the action is executed.
|
||||
The way I solved this was to define a macro YYACT_EPILOGUE that would
|
||||
be invoked after the action. For reasons of symmetry I also added
|
||||
YYACT_PROLOGUE. Although I had no use for that I can envision how it
|
||||
might come in handy for debugging purposes.
|
||||
All is needed is to add
|
||||
|
||||
#if YYLSP_NEEDED
|
||||
YYACT_EPILOGUE (yyval, (yyvsp - yylen), yylen, yyloc, (yylsp - yylen));
|
||||
#else
|
||||
YYACT_EPILOGUE (yyval, (yyvsp - yylen), yylen);
|
||||
#endif
|
||||
|
||||
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.
|
||||
|
||||
* Better graphics
|
||||
Equip the parser with a means to create the (visual) parse tree.
|
||||
|
||||
-----
|
||||
|
||||
Copyright (C) 2001, 2002, 2003, 2004, 2006 Free Software Foundation,
|
||||
Inc.
|
||||
|
||||
This file is part of Bison, the GNU Compiler Compiler.
|
||||
|
||||
This program 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 3 of the License, or
|
||||
(at your option) any later version.
|
||||
|
||||
This program 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 this program. If not, see <http://www.gnu.org/licenses/>.
|
||||
Reference in New Issue
Block a user