parenthesis regex

steph_bow has asked for the wisdom of the Perl Monks concerning the following question:

Hello Dear Monks

I have a problem concerning paranthesis

I would like to detect the following expression, such as

(23
[download]

(135
[download]

So I have used :


# use strict;
...
if (($Delay_id =~ /\(\d\d/) || ($Delay_id =~ /\(\d\d\d/)){
            ...
                }
[download]

But I have messages of error, such as :

Use of uninitialized value in concatenation (.) or string at

Comment on parenthesis regex Select or Download Code

Replies are listed 'Best First'.
Re: parenthesis regex by dreadpiratepeter (Priest) on Jun 25, 2008 at 16:51 UTC
I believe you will find that the warning is because $Delay_id is undefined. Or it is an warning elswhere in your code and unrelated, there is nothing structurally wrong with your regex. Although I would have used /\(\d{2,3}/ or /\(\d\d\d?/ instead of 2 separate expressions -pete "Worry is like a rocking chair. It gives you something to do, but it doesn't get you anywhere."	[reply]
Re^2: parenthesis regex by steph_bow (Pilgrim) on Jun 26, 2008 at 08:43 UTC
Thanks a lot for youe help, guys ! I have just found the source of the problem It was because I had values such as (8 so there were not selected by the regex hence the problem That's really nice of you all, thanks a lot for your help !	[reply]
Re: parenthesis regex by moritz (Cardinal) on Jun 25, 2008 at 16:54 UTC
Maybe you forgot to assign a value to `$Delay_id`? BTW commenting the `use strict;` line is about the silliest thing you can do, it installs delayed bugs in your script (badly paraphrasing TimToady). This doesn't warn: `#!/usr/bin/perl use strict; use warnings; my $Delay_id = '(23'; if (($Delay_id =~ /\(\d\d/) \|\| ($Delay_id =~ /\(\d\d\d/)){ print "Matched\n"; }` [download]	[reply] [d/l] [select]
Re: parenthesis regex by ikegami (Patriarch) on Jun 25, 2008 at 17:31 UTC
I agree with apl. You haven't showed us the code that generates that warning. That warning occurs when concatenating an uninitialized variable `$x . "\n"` [download] or when interpolating of an uninitialized variable (that's the "or string" of the error message) `"$x\n"` [download] Those two snippets produce identical code, thus the common warning. You can also get the warning when interpolating into a regexp, but you get a second warning too. `>perl -we"my $x; /$x/" Use of uninitialized value in regexp compilation at -e line 1. Use of uninitialized value in pattern match (m//) at -e line 1.` [download] On a side note, the code you showed us is problematic for other reasons `if (($Delay_id =~ /\(\d\d/) \|\| ($Delay_id =~ /\(\d\d\d/)){` [download] is the same thing as `if ($Delay_id =~ /\(\d\d/){` [download] since anything the second // could match will also be matched by the first //. If you're planning on adding captures, you want `if ($Delay_id =~ /\((\d\d\d?)/){` [download]	[reply] [d/l] [select]
Re: parenthesis regex by apl (Monsignor) on Jun 25, 2008 at 16:52 UTC
You're not showing us the code that contains the concatenation that produces the error. No code from you, no answer from us.	[reply]
Re^2: parenthesis regex by moritz (Cardinal) on Jun 25, 2008 at 17:00 UTC
You're not showing us the code that contains the concatenation that produces the error. First I disagreed, because it says "or string" in the warnings, but then I tested: `perl -wle 'my $a; $a =~ m/foo/' Use of uninitialized value in pattern match (m//) at -e line 1.` [download] So matching against an undefined value is a different warning, and you are right, the relevant code wasn't quoted in the original question, presumably.	[reply] [d/l]