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TODO: update

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Akim Demaille
2019-10-15 07:28:22 +02:00
parent e5cbac98b6
commit ee35055b49
1 changed files with 45 additions and 15 deletions
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@@ -7,9 +7,6 @@ breaks.
Also, we seem to teach YYPRINT very early on, although it should be Also, we seem to teach YYPRINT very early on, although it should be
considered deprecated: %printer is superior. considered deprecated: %printer is superior.
** glr.cc
move glr.c into the yy namespace
** improve syntax errors (UTF-8, internationalization) ** improve syntax errors (UTF-8, internationalization)
Bison depends on the current locale. For instance: Bison depends on the current locale. For instance:
@@ -58,7 +55,7 @@ Maybe we should exhibit the YYUNDEFTOK token. It could also be assigned a
semantic value so that yyerror could be used to report invalid lexemes. semantic value so that yyerror could be used to report invalid lexemes.
* Bison 3.6 * Bison 3.6
** Unit rules ** Unit rules / Injection rules (Akim Demaille)
Maybe we could expand unit rules (or "injections", see Maybe we could expand unit rules (or "injections", see
https://homepages.cwi.nl/~daybuild/daily-books/syntax/2-sdf/sdf.html), i.e., https://homepages.cwi.nl/~daybuild/daily-books/syntax/2-sdf/sdf.html), i.e.,
transform transform
@@ -77,10 +74,11 @@ Practice' is impossible to find, but according to 'Parsing Techniques: a
Practical Guide', it includes information about this issue. Does anybody Practical Guide', it includes information about this issue. Does anybody
have it? have it?
** Injection rules ** clean up (Akim Demaille)
See above. Do not work on these items now, as I (Akim) have branches with a lot of
changes in this area, and no desire to have to fix conflicts. These
cleaning up will happen after my branches have been merged.
** clean up
*** lalr.c *** lalr.c
Introduce a goto struct, and use it in place of from_state/to_state. Introduce a goto struct, and use it in place of from_state/to_state.
Rename states1 as path, length as pathlen. Rename states1 as path, length as pathlen.
@@ -139,12 +137,6 @@ itself uses int (for yylen for instance), yet stack is based on size_t.
Maybe locations should also move to ints. Maybe locations should also move to ints.
** C
Introduce state_type rather than spreading yytype_int16 everywhere?
** glr.c
yyspaceLeft should probably be a pointer diff.
** Graphviz display code thoughts ** Graphviz display code thoughts
The code for the --graph option is over two files: print_graph, and The code for the --graph option is over two files: print_graph, and
graphviz. This is because Bison used to also produce VCG graphs, but since graphviz. This is because Bison used to also produce VCG graphs, but since
@@ -224,11 +216,13 @@ since it is no longer bound to a particular parser, it's just a
(standalone symbol). (standalone symbol).
* Various * Various
** Rewrite glr.cc in C++ ** Rewrite glr.cc in C++ (Valentin Tolmer)
As a matter of fact, it would be very interesting to see how much we can As a matter of fact, it would be very interesting to see how much we can
share between lalr1.cc and glr.cc. Most of the skeletons should be common. share between lalr1.cc and glr.cc. Most of the skeletons should be common.
It would be a very nice source of inspiration for the other languages. It would be a very nice source of inspiration for the other languages.
Valentin Tolmer is working on this.
** YYERRCODE ** YYERRCODE
Defined to 256, but not used, not documented. Probably the token Defined to 256, but not used, not documented. Probably the token
number for the error token, which POSIX wants to be 256, but which number for the error token, which POSIX wants to be 256, but which
@@ -298,6 +292,12 @@ other improvements and also made it faster (probably because memory
management is performed once instead of three times). I suggest that management is performed once instead of three times). I suggest that
we do the same in yacc.c. we do the same in yacc.c.
(Some time later): it's also very nice to have three stacks: it's more dense
as we don't lose bits to padding. For instance the typical stack for states
will use 8 bits, while it is likely to consume 32 bits in a struct.
We need trustworth benching for Bison, for all our backends.
** yysyntax_error ** yysyntax_error
The code bw glr.c and yacc.c is really alike, we can certainly factor The code bw glr.c and yacc.c is really alike, we can certainly factor
some parts. some parts.
@@ -341,7 +341,24 @@ LORIA, INRIA Nancy - Grand Est, Nancy, France
* Extensions * Extensions
** Multiple start symbols ** Multiple start symbols
Would be very useful when parsing closely related languages. Would be very useful when parsing closely related languages. The idea is to
declared several start symbols, for instance
%start: stmt expr
%%
stmt: ...
expr: ...
and to generate parse, parse_stmt and parse_expr. Technically, the above
grammar would be transformed into
%start: yy_start
yy_start: YY_START_STMT stmt | YY_START_EXPR expr
so that there are no conflicts in the grammar (as would undoubtedly happen
with yy_start: stmt | expr). Then all that remains to do is to adjust the
skeletons so that this initial token (YY_START_STMT, YY_START_EXPR) be
shifted first.
** Better error messages ** Better error messages
The users are not provided with enough tools to forge their error messages. The users are not provided with enough tools to forge their error messages.
@@ -359,6 +376,12 @@ should make this reasonably easy to implement.
Bruce Mardle <marblypup@yahoo.co.uk> Bruce Mardle <marblypup@yahoo.co.uk>
https://lists.gnu.org/archive/html/bison-patches/2015-09/msg00000.html https://lists.gnu.org/archive/html/bison-patches/2015-09/msg00000.html
However, there are many other things to do before having such a feature,
because I don't want a % equivalent to #include (which we all learned to
hate). I want something that builds "modules" of grammars, and assembles
them together, paying attention to keep separate bits separates, in
pseudo name spaces.
** Push parsers ** Push parsers
There is demand for push parsers in Java and C++. And GLR I guess. There is demand for push parsers in Java and C++. And GLR I guess.
@@ -385,6 +408,10 @@ 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 part of %if. Akim Demaille thinks it should be in the parser, so as
to avoid falling into another CPP mistake. to avoid falling into another CPP mistake.
(Later): I'm sure there's actually good case for this. People who need that
feature can use m4/cpp on top of Bison. I don't think it is worth the
trouble in Bison itself.
** XML Output ** XML Output
There are couple of available extensions of Bison targeting some XML There are couple of available extensions of Bison targeting some XML
output. Some day we should consider including them. One issue is output. Some day we should consider including them. One issue is
@@ -404,6 +431,9 @@ XML output for GNU Bison
https://lists.gnu.org/archive/html/bug-bison/2016-06/msg00000.html https://lists.gnu.org/archive/html/bug-bison/2016-06/msg00000.html
http://www.cs.cornell.edu/andru/papers/cupex/ http://www.cs.cornell.edu/andru/papers/cupex/
Andrew Myers and Vincent Imbimbo are working on this item, see
https://github.com/akimd/bison/issues/12
* Coding system independence * Coding system independence
Paul notes: Paul notes: