Over the weekend I started playing with Parse::RecDescent and decided to apply it to a real world problem. Now perhaps using a tool this powerful for what I want to do is gross overkill, but it seemed that using it resulted in less code that is more maintainable than hand rolling a parser. Seeing how much advice in the monastery tends to argue that maintainable code is superior to faster code this route seemed ideal. Unfortunately using Parse::RecDescent is _much_ slower than I would like. So my question is threefold

• Should I even be using Parse::RecDescent at all?
• Can I change the grammer to make it more efficient?
• Are there any recommendations for what is in effect my first attempt at using this very cool tool.

The data (a file) that I need to parse looks like this:

HDRCOMPNAME BIG000OLD111IDENTIFIER1020301WITH1010LOTS1010OF1010CRAP
ADD,1234567890,,COMPNAME
ADDRANGE,2468,4680,COMPNAME
DELETE,987654321,,COMPNAME
DELETERANGE,13579,13599,COMPNAME
TLR000004
[download]

and the grammer I am using looks like this:

my $Grammar=<<'END_GRAMMAR';

startrule   :   file

file        :   header record(s?) trailer_t
                { $return={
                           header=>$item[1],
                           records=>$item[2],
                           count=>$item[3]
                          } 
                }

header      :   header_t data_t
                { 
                 $return={
                          company=>$item[1],
                          code=>$item[2]
                         } 
                }

record      :   valid_rec | <error>

valid_rec   :   type_t ',' number_t ',' number_t(?) ',' name_t
                { $return=[
                           $item[1],
                           $item[3],
                           @{$item[5]} ? $item[5] : undef,
                           $item[7]
                          ] 
                }

header_t    :   /HDR\w+/ { $return=substr($item[1],3) }
trailer_t   :   /TLR\d+/ { $return=substr($item[1],3) }

data_t      :   /\w+/
type_t      :   /ADD(?:RANGE)?|DELETE(?:RANGE)/
number_t    :   /\d+/
name_t      :   /\w+/

END_GRAMMAR
[download]

If its not obvious I have used the postfix _t for tokens.

Any wisdom regarding this would be really appreciated. Especially if there is some way to modify the grammer to enhance speed. These files can contain thousands+ records and the speed hit is seriously making me think of hand rolling this (which I really really dont want to do).

Thanks in advance,

Yves / DeMerphq
--
This space for rent.

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