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

Hello

,

I have following string

 $str = "f3333_4444_2222";

I want to replace the string and make it

 $str = "f1_2_3"

The regexp i am using is

%Hidlabels = {3333=>1, 4444=>2, 2222=>3};
$formula =~ s/f(\d+)/$labels{ $Hidlabels{$1} }/g;

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but this replaces everything with 1. ne ideas?

Replies are listed 'Best First'.
Re: help required for regexp
by Eliya (Vicar) on Dec 07, 2011 at 09:15 UTC

    What is %labels?  Also, your declaration of %Hidlabels should use parentheses, not curlies.  As for the regex, you're matching on f(\d+), which only occurs once in the string...

    This works for me: 

    my $str = "f3333_4444_2222";
my %Hidlabels = ( 3333=>1, 4444=>2, 2222=>3 );
$str =~ s/(\d+)/$Hidlabels{$1}/g;

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Re: help required for regexp
by BrowserUk (Patriarch) on Dec 07, 2011 at 09:25 UTC

    Take a look at the transliteration operator, tr///: 

    $str = "f3333_4444_2222";;

$str =~ tr[342][123]s;;

print $str;;
f1_2_3

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    With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday'
    Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
    "Science is about questioning the status quo. Questioning authority".
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    The start of some sanity?
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Re: help required for regexp
by si_lence (Deacon) on Dec 07, 2011 at 09:25 UTC
    If your example is not a simplified case to illustrate your problem you could also use 
    $str =~ s/(\d)\d+/$1/g;

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Re: help required for regexp
by Corion (Patriarch) on Dec 07, 2011 at 09:36 UTC

    Maybe you want the /e switch (see perlre)?

    %Hidlabels = {3333=>1, 4444=>2, 2222=>3};
$formula =~ s/f(\d+)/$Hidlabels{$1}/ge;

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      Why /e ?  The substitution side behaves like a double quoted string, so $Hidlabels{$1} already interpolates.

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        Uh - yes - I'm not thinking clearly.

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Re: help required for regexp
by AnomalousMonk (Archbishop) on Dec 07, 2011 at 22:32 UTC

    I may be reading too much into the OP, but if upaksh wants to translate digit groups in strings like 'f3333_4444_2222' only when the prefix character is an 'f', the other solutions fail (as shown below). Here are a couple of approaches: 

    >perl -wMstrict -le
"my %Hidlabels = ('3333' => '1',  '4444' => '2',  '2222' => '3');
 my $t =
   'f3333_4444_2222  g4444_2222_3333  f4444_2222_3333  f3333  _3333';
 ;;
 my $s = $t;
 $s =~ s{ (\d+) }{$Hidlabels{$1}}xmsg;
 print qq{'$s'};
 ;;
 $s = $t;
 $s =~ s{ (?: \G (?<! \A) _ | f) \K  (\d+) }{$Hidlabels{$1}}xmsg;
 print qq{'$s'};
 ;;
 $s = $t;
 my $f = qr{ f \d{4} (?: _ \d{4}){2} }xms;
 $s =~ s{ ($f) }
        { (my $x = $1) =~ s{(\d+)}{$Hidlabels{$1}}xmsg;  $x; }xmsge;
 print qq{'$s'};
"
'f1_2_3  g2_3_1  f2_3_1  f1  _1'
'f1_2_3  g4444_2222_3333  f2_3_1  f1  _3333'
'f1_2_3  g4444_2222_3333  f2_3_1  f3333  _3333'

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Re: help required for regexp
by sumeetgrover (Monk) on Dec 07, 2011 at 15:55 UTC

    The first part of your regular expression would only match:
    f3333
    And therefore replace 3333 with 1. Also, you haven't mentioned the %labels hash but used it in regexp.

    Your regexp can be made more specific and changed to:
     $formula=~s/([0-9]{4})/$Hidlabels{$1}/g;

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Re: help required for regexp
by tobyink (Canon) on Dec 08, 2011 at 12:41 UTC 
    %Hidlabels = (3333=>1, 4444=>2, 2222=>3);
$formula =~ s{ (\d+) }
             { defined $Hidlabels{$1} ? $Hidlabels{$1} : $1 }xeg
             if $formula =~ /^f/;

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Re: help required for regexp
by pvaldes (Chaplain) on Dec 07, 2011 at 19:01 UTC

    I want to replace the string and make it

    Simply assign a new value to the variable, regexp are slow, don't use it if you can cheat:

     $str = "f1_2_3";
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Re: help required for regexp
by TJPride (Pilgrim) on Dec 07, 2011 at 11:23 UTC
    Nobody seems to have posted a complete solution that actually works.

    use strict;
use warnings;

my %Hidlabels = ( '3333' => 1, '4444' => 2, '2222' => 3 );
my $str = 'f3333_4444_2222';

$str =~ s/f(\d+)/$Hidlabels{$1}/g;
print $str;

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      Nobody seems to have posted a complete solution that actually works.
      Neither did you.
      Update: Eliya's solution seems to work.
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        Odd, I could have sworn I read all the posts on the way by. If not, then I apologize for posting essentially a duplicate solution. However, mine does in fact work if you run it, so you're wrong on that.
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