Re: Enhancement Request

[Domingo Alvarez Duarte]

Hello Kaz !

As I said before here in the list, I also have that need for other 
purposes (compare, reuse, convert, ... grammars) and did that first with 
byacc and then lemon and bison here 
https://github.com/mingodad/lalr-parser-test

For example here is what I call naked grammar from bison 3.8.2:

====

bison-nb --help
Usage: bison-nb [OPTION]... FILE
Generate a deterministic LR or generalized LR (GLR) parser employing
LALR(1), IELR(1), or canonical LR(1) parser tables.

Mandatory arguments to long options are mandatory for short options too.
The same is true for optional arguments.

Operation Modes:
  -h, --help                 display this help and exit
  -V, --version              output version information and exit
      --print-localedir      output directory containing 
locale-dependent data
                             and exit
      --print-datadir        output directory containing skeletons and XSLT
                             and exit
  -u, --update               apply fixes to the source grammar file and 
exit
  -f, --feature[=FEATURES]   activate miscellaneous features

FEATURES is a list of comma separated words that can include:
  caret, diagnostics-show-caret
                    show errors with carets
  fixit, diagnostics-parseable-fixits
                    show machine-readable fixes
  syntax-only       do not generate any file
  all               all of the above
  none              disable all of the above

Diagnostics:
  -W, --warnings[=CATEGORY]  report the warnings falling in CATEGORY
      --color[=WHEN]         whether to colorize the diagnostics
      --style=FILE           specify the CSS FILE for colorizer diagnostics

Warning categories include:
  conflicts-sr      S/R conflicts (enabled by default)
  conflicts-rr      R/R conflicts (enabled by default)
  counterexamples, cex
                    generate conflict counterexamples
  dangling-alias    string aliases not attached to a symbol
  deprecated        obsolete constructs
  empty-rule        empty rules without %empty
  midrule-values    unset or unused midrule values
  precedence        useless precedence and associativity
  yacc              incompatibilities with POSIX Yacc
  other             all other warnings (enabled by default)
  all               all the warnings except 'counterexamples', 
'dangling-alias' and 'yacc'
  no-CATEGORY       turn off warnings in CATEGORY
  none              turn off all the warnings
  error[=CATEGORY]  treat warnings as errors

WHEN can be one of the following:
  always, yes  colorize the output
  never, no    don't colorize the output
  auto, tty    colorize if the output device is a tty

Tuning the Parser:
  -L, --language=LANGUAGE          specify the output programming language
  -S, --skeleton=FILE              specify the skeleton to use
  -t, --debug                      instrument the parser for tracing
                                   same as '-Dparse.trace'
      --locations                  enable location support
  -D, --define=NAME[=VALUE]        similar to '%define NAME VALUE'
  -F, --force-define=NAME[=VALUE]  override '%define NAME VALUE'
  -p, --name-prefix=PREFIX         prepend PREFIX to the external symbols
                                   deprecated by '-Dapi.prefix={PREFIX}'
  -l, --no-lines                   don't generate '#line' directives
  -k, --token-table                include a table of token names
  -y, --yacc                       emulate POSIX Yacc
  -z, --noprec                     ignore all precedences

Output Files:
  -e                            generate RREBNF
  -n                            generate naked grammar
  -N                            generate lemon grammar
  -s                            generate sql
  -H, --header=[FILE]           also produce a header file
  -d                            likewise but cannot specify FILE (for 
POSIX Yacc)
  -r, --report=THINGS           also produce details on the automaton
      --report-file=FILE        write report to FILE
  -v, --verbose                 same as '--report=state'
  -b, --file-prefix=PREFIX      specify a PREFIX for output files
  -o, --output=FILE             leave output to FILE
  -g, --graph[=FILE]            also output a graph of the automaton
      --html[=FILE]             also output an HTML report of the automaton
  -x, --xml[=FILE]              also output an XML report of the automaton
  -M, --file-prefix-map=OLD=NEW replace prefix OLD with NEW when 
writing file paths
                                in output files

THINGS is a list of comma separated words that can include:
  states            describe the states
  itemsets          complete the core item sets with their closure
  lookaheads        explicitly associate lookahead tokens to items
  solved            describe shift/reduce conflicts solving
  counterexamples, cex
                    generate conflict counterexamples
  all               include all the above information
  none              disable the report

Report bugs to <bug-bison@gnu.org>.
GNU Bison home page: <https://www.gnu.org/software/bison/>.
General help using GNU software: <https://www.gnu.org/gethelp/>.
Report translation bugs to <https://translationproject.org/team/>.
For complete documentation, run: info bison.
====

====

bison-nb -n parse-gram.y

/*Tokens*/
%token YYEOF
%token YYerror
%token YYUNDEF
%token STRING
%token TSTRING
%token PERCENT_TOKEN
%token PERCENT_NTERM
%token PERCENT_TYPE
%token PERCENT_DESTRUCTOR
%token PERCENT_PRINTER
%token PERCENT_LEFT
%token PERCENT_RIGHT
%token PERCENT_NONASSOC
%token PERCENT_PRECEDENCE
%token PERCENT_PREC
%token PERCENT_DPREC
%token PERCENT_MERGE
%token PERCENT_CODE
%token PERCENT_DEFAULT_PREC
%token PERCENT_DEFINE
%token PERCENT_ERROR_VERBOSE
%token PERCENT_EXPECT
%token PERCENT_EXPECT_RR
%token PERCENT_FILE_PREFIX
%token PERCENT_FLAG
%token PERCENT_GLR_PARSER
%token PERCENT_HEADER
%token PERCENT_INITIAL_ACTION
%token PERCENT_LANGUAGE
%token PERCENT_NAME_PREFIX
%token PERCENT_NO_DEFAULT_PREC
%token PERCENT_NO_LINES
%token PERCENT_NONDETERMINISTIC_PARSER
%token PERCENT_OUTPUT
%token PERCENT_PURE_PARSER
%token PERCENT_REQUIRE
%token PERCENT_SKELETON
%token PERCENT_START
%token PERCENT_TOKEN_TABLE
%token PERCENT_VERBOSE
%token PERCENT_YACC
%token BRACED_CODE
%token BRACED_PREDICATE
%token BRACKETED_ID
%token CHAR_LITERAL
%token COLON
%token EPILOGUE
%token EQUAL
%token ID
%token ID_COLON
%token PERCENT_PERCENT
%token PIPE
%token PROLOGUE
%token SEMICOLON
%token TAG
%token TAG_ANY
%token TAG_NONE
%token INT_LITERAL
%token PERCENT_PARAM
%token PERCENT_UNION
%token PERCENT_EMPTY


%start input

%%

input :
    YYEOF
    | prologue_declarations "%%" grammar epilogue.opt
    ;

prologue_declarations :
    /*empty*/
    | prologue_declarations prologue_declaration
    ;

prologue_declaration :
    grammar_declaration
    | "%{...%}"
    | "%<flag>"
    | "%define" variable value
    | "%header" string.opt
    | "%error-verbose"
    | "%expect" INT_LITERAL
    | "%expect-rr" INT_LITERAL
    | "%file-prefix" STRING
    | "%glr-parser"
    | "%initial-action" "{...}"
    | "%language" STRING
    | "%name-prefix" STRING
    | "%no-lines"
    | "%nondeterministic-parser"
    | "%output" STRING
    | "%param" params
    | "%pure-parser"
    | "%require" STRING
    | "%skeleton" STRING
    | "%token-table"
    | "%verbose"
    | "%yacc"
    | error ";"
    | ";"
    ;

params :
    params "{...}"
    | "{...}"
    ;

grammar_declaration :
    symbol_declaration
    | "%start" symbols.1
    | code_props_type "{...}" generic_symlist
    | "%default-prec"
    | "%no-default-prec"
    | "%code" "{...}"
    | "%code" ID "{...}"
    ;

code_props_type :
    "%destructor"
    | "%printer"
    ;

union_name :
    /*empty*/
    | ID
    ;

grammar_declaration :
    "%union" union_name "{...}"
    ;

symbol_declaration :
    "%nterm" nterm_decls
    | "%token" token_decls
    | "%type" symbol_decls
    | precedence_declarator token_decls_for_prec
    ;

precedence_declarator :
    "%left"
    | "%right"
    | "%nonassoc"
    | "%precedence"
    ;

string.opt :
    /*empty*/
    | STRING
    ;

tag.opt :
    /*empty*/
    | TAG
    ;

generic_symlist :
    generic_symlist_item
    | generic_symlist generic_symlist_item
    ;

generic_symlist_item :
    symbol
    | tag
    ;

tag :
    TAG
    | "<*>"
    | "<>"
    ;

nterm_decls :
    token_decls
    ;

token_decls :
    token_decl.1
    | TAG token_decl.1
    | token_decls TAG token_decl.1
    ;

token_decl.1 :
    token_decl
    | token_decl.1 token_decl
    ;

token_decl :
    id int.opt alias
    ;

int.opt :
    /*empty*/
    | INT_LITERAL
    ;

alias :
    /*empty*/
    | string_as_id
    | TSTRING
    ;

token_decls_for_prec :
    token_decl_for_prec.1
    | TAG token_decl_for_prec.1
    | token_decls_for_prec TAG token_decl_for_prec.1
    ;

token_decl_for_prec.1 :
    token_decl_for_prec
    | token_decl_for_prec.1 token_decl_for_prec
    ;

token_decl_for_prec :
    id int.opt
    | string_as_id
    ;

symbol_decls :
    symbols.1
    | TAG symbols.1
    | symbol_decls TAG symbols.1
    ;

symbols.1 :
    symbol
    | symbols.1 symbol
    ;

grammar :
    rules_or_grammar_declaration
    | grammar rules_or_grammar_declaration
    ;

rules_or_grammar_declaration :
    rules
    | grammar_declaration ";"
    | error ";"
    ;

rules :
    id_colon named_ref.opt ":" rhses.1
    ;

rhses.1 :
    rhs
    | rhses.1 "|" rhs
    | rhses.1 ";"
    ;

rhs :
    /*empty*/
    | rhs symbol named_ref.opt
    | rhs tag.opt "{...}" named_ref.opt
    | rhs "%?{...}"
    | rhs "%empty"
    | rhs "%prec" symbol
    | rhs "%dprec" INT_LITERAL
    | rhs "%merge" TAG
    | rhs "%expect" INT_LITERAL
    | rhs "%expect-rr" INT_LITERAL
    ;

named_ref.opt :
    /*empty*/
    | BRACKETED_ID
    ;

variable :
    ID
    ;

value :
    /*empty*/
    | ID
    | STRING
    | "{...}"
    ;

id :
    ID
    | CHAR_LITERAL
    ;

id_colon :
    ID_COLON
    ;

symbol :
    id
    | string_as_id
    ;

string_as_id :
    STRING
    ;

epilogue.opt :
    /*empty*/
    | "%%" EPILOGUE
    ;

====

Cheers !

On 19/6/22 19:58, Kaz Kylheku wrote:
> On 2022-06-17 10:58, slipbits wrote:
> > Given that Bison has the ability to (and does) generate a parser for
> > itself, is there any possibility of removing all %code tags in future releases.
> This is not clear; remove what from where? For what purpose?
>
> How does Bison being partially self-hosted play into the removal?
>
> > This means that one code block, %code { declarations }, is all that is
> > required and removes the placement requirements and discussion in
> > the Bison User's Manual.
> By tag, do you want to remove the %code <qualifier> feature?
>  From where?
>
> The Bison grammar file parse-gram.y uses multiple
> %oode <qualifier> construcs.
>
> Are you looking to edit that file so that it has only one unqualified
> %code block?
>
> Why shouldn't it it have multiple, qualified blocks?
> This is a documented feature of Bison; the Bison grammar is just
> "eating the dogfood", which is good.
>
> Bison ships the generated parser as parse-gram.c, which means that
> it builds without needing an installation of Bison, and the grammar
> file can use the latest features provided in that same version
> of Bison.
>
> Removing the multiple qualified %oode blocks from Bison's own
> grammer would just mean that the feature is exercised less.
>
> The documentation makes it clear that the %code feature makes
> placement less important compared to the traditional %{ ... %}
> Bison gathers code from multiple %code blocks, then catenates
> them together (by qualifier) type. For any qualifier, the order
> is preserved. The code is then generated into the appropriate
> location based on the output type.