X-Git-Url: https://git.saurik.com/bison.git/blobdiff_plain/d4e7d3a1919c20a6dbf5eb4cfa62cb6228a0e48d..6c35d22c399d53cc4ce2b0f594a3033ede3ae117:/TODO diff --git a/TODO b/TODO index 4780351f..d3725032 100644 --- a/TODO +++ b/TODO @@ -1,5 +1,41 @@ -*- outline -*- +* URGENT: Documenting C++ output +Write a first documentation for C++ output. + +* 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 $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, ?). + +* Error messages +Some are really funky. For instance + + 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? + +* Documentation +Some history of Bison and some bibliography would be most welcome. +Are there any Texinfo standards for bibliography? + * 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_ @@ -21,109 +57,10 @@ When implementing multiple-%union support, bare the following in mind: char *sval; } -* Experimental report features -Decide whether they should be enabled, or optional. For instance, on: - - input: - exp - | input exp - ; - - exp: - token1 "1" - | token2 "2" - | token3 "3" - ; - - token1: token; - token2: token; - token3: token; - -the traditional Bison reports: - - state 0 - - $axiom -> . input $ (rule 0) - - token shift, and go to state 1 - - 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 - - token1 -> token . (rule 6) - token2 -> token . (rule 7) - token3 -> token . (rule 8) - - "2" reduce using rule 7 (token2) - "3" reduce using rule 8 (token3) - $default reduce using rule 6 (token1) - -while with --trace, i.e., when enabling both the display of non-core -item sets and the display of lookaheads, Bison now displays: - - state 0 - - $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 - - 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 - - token1 -> token . ["1"] (rule 6) - token2 -> token . ["2"] (rule 7) - token3 -> token . ["3"] (rule 8) - - "2" reduce using rule 7 (token2) - "3" reduce using rule 8 (token3) - $default reduce using rule 6 (token1) - -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: - - state 0 - Core: - $axiom -> . input $ (rule 0) - - 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) - - token shift, and go to state 1 - - 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 - - -Note that the same questions applies to --graph. +* --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: @@ -221,7 +158,10 @@ into exp: exp '+' exp | exp '&' exp; when there are no actions. This can significantly speed up some -grammars. +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? * Stupid error messages An example shows it easily: @@ -247,11 +187,6 @@ 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. @@ -361,9 +296,6 @@ 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. - * RR conflicts See if we can use precedence between rules to solve RR conflicts. See what POSIX says. @@ -381,19 +313,8 @@ 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" -Subject: Token Alias Bug -To: "'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.) +I'm on it! I already have a proto that parses (but the actions are +not fully written yet). -- Akim * $undefined From Hans: @@ -419,9 +340,6 @@ a Bison option where every typed default rule is explicitly written out 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 them, it is fairly well described there. It would be very nice to @@ -460,6 +378,10 @@ 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. + ----- Copyright (C) 2001, 2002 Free Software Foundation, Inc.