Parse.y (was Ripper and 1.8)

Ruby
1

Hi all,

I’ve been poking around Ripper for the last couple a days and during
that process I started to look at parse.y as it’s currently in CVS (Ruby
1.9 that is).
I’m not very knowledgeable about yacc and parsers in general but I just
wanted to ask a quick question.

In parse.y I see alot of /%%%/ and /% --code-- %/“constructs” for
example:

primary : literal
| strings
| xstring
| regexp
| words
| qwords
| var_ref
| backref
| tFID
{
/%%%/
$$ = NEW_FCALL($1, 0);
/%
$$ = method_arg(dispatch1(fcall, $1),
arg_new());
%/
}

I’ve started reading the bison manual but I can’t find any reference to
this construct.
My question: Are these lines just comments or are they instructing
bison?

Again, any help is greatly appreciated.

With kind regards,
Jonathan

2

“J” == Jonathan M. [email protected] writes:

J> In parse.y I see alot of /%%%/ and /% --code-- %/“constructs” for

Look at the file

ruby/ext/ripper/tools/preproc.rb

Guy Decoux

3

Jonathan M. wrote:

               /*%%%*/
                   $$ = NEW_FCALL($1, 0);
               /*%
                   $$ = method_arg(dispatch1(fcall, $1), arg_new());
               %*/

It’s a construct needed for Ripper.

For Bison, the code of the first line is normal code, the second is
comment. So the relevant part for Bison is:

$$ = NEW_FCALL($1, 0);

In Ripper, there needs to be different code, so a script preprocesses
the whole parse.y, removes the text from /%%% to /% and removes the
%*/, so the second code line is relevant:

$$ = method_arg(dispatch1(fcall, $1), arg_new());

Have a look at ext/ripper/tools/preproc.rb to see how the preprocessing
works in detail.

Robin S.