RFC: %param

[Akim Demaille]

Hi,

I was tired to read

> %parse-param {::parser::ParserImpl& up}
> %lex-param {::parser::ParserImpl& up}
> %parse-param {yyFlexLexer& scanner}
> %lex-param {yyFlexLexer& scanner}

in my code, I wanted

> %param {::parser::ParserImpl& up}{yyFlexLexer& scanner};

I pushed this feature in candidates/%param, but there are several  
issues:

- I had not noticed, but when I started upgrading the documentation, I  
discovered that in lalr1.java, the %lex-params are added to the  
signature of yyparse, which in my case would have allowed to use only  
%lex-params.  It makes sense, but I am uncomfortable with the  
coexistence of several conventions within Bison.

- I like to keep related things close to each other.  But sometimes it  
can clutter the code.  Here, as often in my grammars, I have put  
together everything related to %(lex-|parse-)?param management, but it  
disrupts the reading of the grammar.  What do people prefer?   
Currently, it reads:

> /*---------.
> | %param.  |
> `---------*/
> %code requires
> {
> # ifndef PARAM_TYPE
> #  define PARAM_TYPE
>   typedef enum
>   {
>     param_none  = 0,
>     param_lex   = 1 << 0,
>     param_parse = 1 << 1,
>     param_both  = param_lex | param_parse
>   } param_type;
> # endif
> };
> %code
> {
>   /** Add a lex-param and/or a parse-param.
>    *
>    * \param type  where to push this formal argument.
>    * \param decl  the formal argument.  Destroyed.
>    * \param loc   the location in the source.
>    */
>   static void add_param (param_type type, char *decl, location loc);
>   static param_type current_param = param_none;
> };
> %union
> {
>   param_type param;
> };
> %token <param> PERCENT_PARAM "%param";
> %printer
> {
>   switch ($$)
>     {
> #define CASE(In, Out)                                           \
>       case param_ ## In: fputs ("%" #Out, stderr); break
>       CASE(lex,   lex-param);
>       CASE(parse, parse-param);
>       CASE(both,  param);
> #undef CASE
>     }
> } <param>;
>
> prologue_declaration:
>   "%param" { current_param = $1; } params { current_param =  
> param_none; }
> ;
>
> params:
>    params "{...}"  { add_param (current_param, $2, @2); }
> | "{...}"          { add_param (current_param, $1, @1); }
> ;

- I have not written the test suite yet, but I'm using the feature.

0001-param.txt
Description: Text document

0002-Regen.txt
Description: Text document

0003-parse-support-several-arguments.txt
Description: Text document

0004-Regen.txt
Description: Text document

0005-param-documentation.txt
Description: Text document