Perl Guru Forums: Perl Programming Help: Regular Expressions: replacement with exact number of chars

CGI/Perl Guide | Learning Center | Forums | Advertise | Login

Site Search: in


	MAIN INDEX	SEARCH POSTS	WHO'S ONLINE	LOG IN

Home: Perl Programming Help: Regular Expressions:
replacement with exact number of chars

Anglachel
Novice

Dec 3, 2010, 8:29 AM

Post #1 of 4 (6065 views)

replacement with exact number of chars	Can't Post

Sorry for basic question. How I can replace some pattern with the exact number of characters?
Let's say I have a string AAAABBBBCCCC and variables that keep start and end positions of B (characters defined here with B in real world could be any, I just know only position of pattern I want to replace not pattern itself). And I want to replace this pattern with the same number (known for me) of X characters.
So I use

Code

my $range = $end-$start; 
$string =~ s/^(.{$start})(.{$range})(.*)$/$1?{$range}$3/;

What should I use on the place of question mark?
Now I'm using rather awkward construction:

Code

for (my $j=0; $j<$range; $j++) { 
      $x .= "X";  }

(the $x plays instead of question mark in my expression)
Any help would be appreciated!

(This post was edited by Anglachel on Dec 3, 2010, 8:30 AM)

Zhris
Enthusiast

Dec 5, 2010, 1:34 PM

Post #2 of 4 (5888 views)

Re: [Anglachel] replacement with exact number of chars [In reply to]	Can't Post

I think it would be best if you used the substr function instead of a regular expression:

Code

#!/usr/bin/perl 
use strict; 
use warnings; 
 
my $string = 'AAAABBBBCCCC'; 
print "$string\n"; 
 
my $replace_char = 'X'; 
my $replace_start = "4"; 
my $replace_end = "8"; 
 
my $replace_range = $replace_end - $replace_start; 
 
my $replace_string; 
for (1 .. $replace_range) { 
	$replace_string .= $replace_char; 
} 
 
substr ($string, $replace_start, $replace_range) = $replace_string; 
print "$string\n";

Chris

(This post was edited by Zhris on Dec 5, 2010, 1:37 PM)

rovf
Veteran

Dec 6, 2010, 2:05 AM

Post #3 of 4 (5825 views)

Re: [Anglachel] replacement with exact number of chars [In reply to]	Can't Post

Code

substr($s,$p,$m) = $t x $n

replaces the $m characters in string $s, starting at position $p, by $n occurences of string $t.

Code

$s =~ tr/B/X/

replaces in string $s all occurances of the letter B by the letter X.

Anglachel
Novice

Dec 8, 2010, 8:58 AM

Post #4 of 4 (5645 views)

Re: [Anglachel] replacement with exact number of chars [In reply to]	Can't Post

Thank you for help! I was also driven to use substr due to the problem of the quantifier limit 32766 in regex. Smile

Search for (options)

Web Applications & Managed Hosting Powered by Gossamer Threads
Visit our Mailing List Archives