Re: passing text by reference and other questions...

hmm, i was looking at the archives and it seems the text of my message
got lost...interesting....

i'm resending the message which was supposed to accompany those
patches.

note: this is long....

<original message>

assuming $parser is the Parse::RecDescent object and $text is the
source text:

1) if i pass $text by reference ($parser->start_rule( \$text )) then
   any text consumed is removed from the beginning of $text, even if
   this does not lead to a complete match. is this the way it's
   supposed to work?

example:

$grammar = q{ start_rule : 'foo' 'bar' }

$text = ' foo would never eat in a bar '

when i do $parser->start_rule(\$text) even though this fails to match
any rules $text is now: ' would never eat in a bar '.

2) can i have a grammar which does not define the structure of my
   entire text and yet still have it match in thoses places of the
   text where it could match?

example:

$grammar = q { start_rule : 'french' 'fries' }

$text = " i like french fries ";

if i pass $text to $parser->start_rule it will not match because,
rightfully so, ' i' does not start any rule, however since i have to
basically do this i currently have the hurendously (sp?) inefficent:

my $rest_buffer = $text;
my $seen_buffer = "";
while ($rest_buffer ne '') {
  $parser->start_rule( $rest_buffer );
  $seen_buffer = substr($rest_buffer, 0, 1);
  $rest_buffer = substr($rest_buffer, 1);
}

$text = $seen_buffer;

(i can't even skip ahead by white space since white space is important
to me, and while in this case i could just look for those points
starting with 'french' in the general case i do not know what the
grammar looks like, so this isn't possible)

i'd appreciate any suggestions.

3) i needed the <perl_codeblock> directive to allow me to pass the
   delimiters to Text::Balaned::extract_codeblock, i have attached a
   patch to RecDesecent.pm which allows this in the form of
   <perl_codeblock:[delimiters]>. however, since i don't _really_
   understand RecDesecent.pm it's kindof ugly (i think a
   <bracketed:[delimiters]) directive would be better, but i couldn't
   get that to work. again, any comments/suggestions would be
   appreciated.

4) Since i'm assuming Mr. Conway is listening: [this isn't realted to
   Parse::RecDescent]
  
   i needed to be able to unhide the source code Filter::Simple
   "whites out" when you use the FILTER_ONLY code => sub { }, so am
   attaching a patch which adds a function Filter::Simple::show which
   fills the place holders back in. an inverse hide function would be
   usefull, but i haven't gotten around to it yet. the 5 line patch is
   attached to this email. while i'm at it, is there a filtering stuff
   mailing list?

</original message>

[last night i was doing some more stuff and i came across the following
"problem":]

5) i need to be able to initialize some global variables every time i
   try to parse some text. my start rule is called macro and i have it
   defined as:

  macro : { $Macro::Grammar::new_grammar = init_grammar(); } 
          'macro'
          template
          generator
          { stuff(); }

  the problem is that whnever i have that first action i get lot's of
  errors about an undefined sub rule "1". i tried having the action
  return all kinds of different things (via $return and the last
  value), is was thinking that maybe i needed to return "" or a valid
  token, however i could not get rid of that error. i've read through
  the docs a few (thousand) times and while all the example do show
  actions as the last element/token (what's the propoer terminology
  here?) in a rule i looked at the compiled parser (via
  Parse::RecDescent::Precompile) and i saw that the action is getting
  do'd but then it would seem that the parser tries with the next
  token, no error statements (actually, no other statements at all if
  $::RD_TRACE is undef). so, what am i missing?

i don't know if this will help or not, but here's what i'm trying to
do:

i want to be able to put

  macro { aif <cond:code_block ()> }
        { "if (my \$it = ($cond))" }

in my perl files and have any perl code which matches the rule
(Parse::RecDescent::skip = '') :
  
  macro : 'aif' /\s*/ <perl_codeblock:()>

be transformed into the text:

  if (my $it = (<whatever matched the <perl_codeblock:()>>))

i'm currently doing this by having my parser create a parser for the
macro. 

if you can read this the message got through and we're all shiny happy
people.
-- 
-Marco
Ring the bells that still can ring.
Forget the perfect offering.
There's a crack in everything.
It's how the light gets in.
     -Isonard Cohen