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quantified atoms

pebreo
Novice

May 27, 2005, 12:44 PM

Post #1 of 7 (2305 views)

quantified atoms	Can't Post

Interesting subject, huh? I don't know of any other scripting language that is so eclectic with it's nomenclature. Smile

Well, anyway, here's my question.

I have an html file with tables with some having dozens of rows and others only a few. I want to extract only those tables with a minimum amount of rows. Here's a sample source of html:

Code

# TABLE WITH 3 ROWS 
<table> 
<tr> 1 row </tr> 
<tr> 2 rows </tr> 
<tr> 3 rows </tr> 
</table> 
 
# TABLE WITH 1 ROW 
<table> 
<tr> 1 row </tr> 
</table>

I am able to extract the tables with no problem using a pattern that includes all tables. But I am unable to tell regex that I want it only to match whenever <tr>.+</tr> is encountered three or more time.

Code

# this works: 
# this one extracts tables with rows no matter how many <tr> </tr> tags are in it 
$string =~  m|(<table[^>]*>.+?<tr[^>]*>.+?</tr[^>]*>.+?</table[^>]*>)|sig); 
 
# this doesn't work: 
# why doesn't this one work?  can't i use (?:<tr>.+? </tr>){3,}   
# i even tried (?=<tr>.+? </tr>){3,}  
$string =~  m|(<table[^>]*>.+?(?:<tr[^>]*>.+?</tr[^>]*>){3,}.+?</table[^>]*>)|sig);

Why doesn't regex recognize that quantified atom of (<tr> </tr>)?.
I'm cringing at the thought that I might have to do some recursive regex algorithm. I'd appreciate any ideas.

Thanks for reading.
pebreo

KevinR
Veteran

May 27, 2005, 2:04 PM

Post #2 of 7 (2303 views)

Re: [pebreo] quantified atoms [In reply to]	Can't Post

sounds like a job better suited to an html aware module like HTML::TokeParser. Are there no data cells in the table rows?

<td>content</td>

if I were to try this without a parser I might try something like this (assume html code is consistently written like you posted which is rarley the case with html):

Code

#!perl  
use strict;  
use warnings;  
 
my @AofA; 
my $i = -1; 
my $flag = 0; 
while(<DATA>) { 
   chomp; 
   ($i++,$flag = 1) if (index($_,'<table') > -1); 
   if ($flag == 1) { 
      push @{$AofA[$i]},$1 while (/<tr>(.*?)<\/tr>/ig); 
   } 
   $flag = 0 if (index($_,'</table>') > -1);  
} 
for (@AofA) { 
   print "@{$_}\n" if scalar(@{$_}) == 3; 
} 
 
__DATA__ 
<table>  
<tr> 1 row </tr><tr> 2 rows </tr><tr> 3 rows </tr>  
</table>  
<table>  
<tr> 1 row </tr>  
</table> 
<table>  
<tr> 1 row </tr>  
<tr> 2 rows </tr>  
<tr> 3 rows </tr>  
</table>  
<table>  
<tr> 1 row </tr>  
</table>

like many perl coders are fond of repeating: TIMTOW

Wink

-------------------------------------------------

(This post was edited by KevinR on May 27, 2005, 6:21 PM)

pebreo
Novice

May 28, 2005, 10:51 AM

Post #3 of 7 (2290 views)

Re: [KevinR] quantified atoms [In reply to]	Can't Post

"TIMTOW" I think that's true. I like that!
Thanks for the idea. I ended taking the string and doing another match on it. Like this:

Code

foreach ($string =~  m|(<table[^>]*>.+?(?=<tr[^>]*>.+?</tr[^>]*>).+?</table[^>]*>)|sig) 
	{ 
		$nstring = $_; 
		# print $nstring; 
		print "------- new string ----\n"; 
		if($nstring =~  m|.*(.*<tr[^>]*>.*?</tr[^>]*>.*){5,}?.*|sig) 
		{ 
		   print $nstring; 
		} 
		 
		print "---- end string -----\n"; 
	}

Thanks for ur reply.
Smile

KevinR
Veteran

May 28, 2005, 11:23 AM

Post #4 of 7 (2288 views)

Re: [pebreo] quantified atoms [In reply to]	Can't Post

thats an unusual way to use "foreach", maybe you mean to use "if". "foreach" is generally for looping through a list, and "if" is for a single string.

How are you feeding data into that code block?
-------------------------------------------------

pebreo
Novice

May 28, 2005, 11:34 AM

Post #5 of 7 (2287 views)

Re: [KevinR] quantified atoms [In reply to]	Can't Post

I put the file into one long string:

Code

open(INPUT, "<$filename"); 
undef $/; 
my $string = <INPUT>; 
$/ = "\n";     #Restore for normal behaviour later in script 
close INPUT;

KevinR
Veteran

May 28, 2005, 11:59 AM

Post #6 of 7 (2283 views)

Re: [pebreo] quantified atoms [In reply to]	Can't Post

hmm... doesn't work for me:

Code

#!perl   
use strict;   
use warnings; 
use CGI qw/:standard/; 
print header; 
print '<plaintext>';   
undef $/;  
my $string = <DATA>; 
print "$string\n\n\n";  
my $nstring; 
foreach ($string =~  m|(<table[^>]*>.+?(?=<tr[^>]*>.+?</tr[^>]*>).+?</table[^>]*>)|sig)  
{  
		$nstring = $_;  
		# print $nstring;  
		print "------- new string ----\n";  
		if($nstring =~  m|.*(.*<tr[^>]*>.*?</tr[^>]*>.*){5,}?.*|sig)  
		{  
		   print $nstring;  
		}  
		  
		print "---- end string -----\n";  
}  
  
__DATA__  
<table>   
<tr> 1 row </tr><tr> 2 rows </tr><tr> 3 rows </tr>   
</table>   
<table>   
<tr> 1 row </tr>   
</table>  
<table>   
<tr> 1 row </tr> 
<tr> 2 rows </tr> 
<tr> 3 rows </tr> 
</table>   
<table>   
<tr> 1 row </tr>   
</table>

prints:

Code

<table>   
<tr> 1 row </tr><tr> 2 rows </tr><tr> 3 rows </tr>   
</table>   
<table>   
<tr> 1 row </tr>   
</table>  
<table>   
<tr> 1 row </tr>   
 
<tr> 2 rows </tr>   
<tr> 3 rows </tr>   
</table>   
<table>   
<tr> 1 row </tr>   
</table> 
 
 
 
------- new string ---- 
---- end string ----- 
------- new string ---- 
---- end string ----- 
------- new string ---- 
---- end string ----- 
------- new string ---- 
---- end string -----

-------------------------------------------------

pebreo
Novice

May 30, 2005, 8:21 AM

Post #7 of 7 (2255 views)

Re: [KevinR] quantified atoms [In reply to]	Can't Post

Right, because the quantifier is {5,}. I had to mess around with the quantifier to get it to work the way I wanted.

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