Re: better way to convert a string into an array and an hash

use strict;
use warnings;

my $string = "1:1,2:1,3:2,500:2,505:1";
my (@array, %hash);


$string =~ s/(\d+):(\d+)(?:,|$)/$hash{$1}=$2;push(@array, $1)/ge;

use Data::Dumper;

print Dumper(\@array, \%hash);
[download]

the e on the end of the s// tells perl to execute what's on the right hand side and the g tells it to match the left hand side as many times as possible. So you effectively end up with the code on the right in a loop over all the things that match the pattern.

The (?:,|$) makes sure that the pair of number si followed by a , or that we're at the end of the string.

One thing to note is that this will destroy the contents of $string.

Comment on Re: better way to convert a string into an array and an hash Download Code

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Re^2: better way to convert a string into an array and an hash by ikegami (Patriarch) on Oct 05, 2004 at 18:44 UTC
May I recommend `while ($string =~ /(\d+):(\d+)(?:,\|$)/g) { $hash{$1} = $2; push(@array, $1); }` [download] over `$string =~ s/(\d+):(\d+)(?:,\|$)/$hash{$1}=$2;push(@array, $1)/ge;` [download]	[reply] [d/l] [select]
Re^2: better way to convert a string into an array and an hash by ambrus (Abbot) on Oct 05, 2004 at 18:45 UTC
You are using `s///ge` only for the side effects of the code in the substitution part. Why do you need a substitution then? You could just as well say `use warnings; use strict; my $string = "1:1,2:1,3:2,500:2,505:1"; my (@array, %hash); while ($string =~ /(\d+):(\d+)(?:,\|$)/g) { $hash{$1}=$2;push(@array, $1) }; use Data::Dumper; print Dumper(\@array, \%hash);` [download]	[reply] [d/l] [select]
Re^3: better way to convert a string into an array and an hash by fergal (Chaplain) on Oct 05, 2004 at 20:50 UTC
Simply because it gives you a free loop. I first saw this idiom about 10 years ago for decoding a cgi params into a hash. Something like `$p =~ s/(.?)=(.?)(&\|$)/$v=$2;$v=~s/%(..)/chr(hex($1))/ge;$p{$1}=$v/g +e` [download] a substitution within a substiution! I also thought it might be quicker but after a quick benchmark it seems not. I suppose I could have used `[/(\d+):(\d+)(?:,\|$)(?{$hash{$1}=$2;push(@array, $1);1})/g];` [download] for a free loop without destroying the string but isn't much faster.	[reply] [d/l] [select]