Re: Formatting a number

This is not really answering the OP as it is not a one-liner nor does it use a regex. But, in the spirit of TIMTOWTDI

use strict;
use warnings;

printf qq{%20s\n}, comma3($_)
   for (12, 1234, 1234567, 1234567890);

sub comma3
{
    my $ct = 0;
    join q{},
       reverse map {++ $ct % 3 ? $_ : ($_, q{,})}
       reverse split m{}, $_[0];
}
[download]

produces

                  12
               1,234
           1,234,567
       1,234,567,890
[download]

Cheers,

JohnGG

Update: Subroutine was erroneously putting commas at the front of numbers with lengths divisble by three, thanks jwkrahn for pointing this out. Revised subroutine (which is, of course, even slower) below

sub comma3
{
    my $ct = 0;
    my $len = length $_[0];
    return join q{},
       reverse map
       {
           ++ $ct % 3
              ? $_
              : $ct == $len
                 ? $_
                 : ($_, q{,})
       }
       reverse split m{}, $_[0];
}
[download]

Benchmarks will be updated in a bit.

Comment on Re: Formatting a number Select or Download Code

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Re^2: Formatting a number by jwkrahn (Abbot) on Oct 16, 2006 at 19:09 UTC
`$ perl -le' my $number = 123456789; my $ct = 0; $number = join q{}, reverse map { ++$ct % 3 ? $_ : ( $_, q{,} ) } reverse split //, $number; print $number; ' ,123,456,789` [download] Oops, You have an extra comma at the beginning.	[reply] [d/l]
Re^3: Formatting a number by johngg (Canon) on Oct 16, 2006 at 21:49 UTC
So, not only slow but wrong, damn!	[reply]