Splitting array into two with a regex

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

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Re: Splitting array into two with a regex by Fletch (Bishop) on Nov 08, 2005 at 14:46 UTC
`my( @ok, @no ); push @{ $_->name =~ /\d{2}$/ ? \@ok : \@no }, $_ for @{ $rec->vals }` [download] Update: Heh, I was going to mention Ruby as well.	[reply] [d/l]
Re^2: Splitting array into two with a regex by Anonymous Monk on Nov 08, 2005 at 15:01 UTC
Could you explain what does it mean @{$rec->vals}. Is it array ref? Could you give me an example of datastructure how it will look like. I am eager to learn the concept.	[reply]
Re^3: Splitting array into two with a regex by reasonablekeith (Deacon) on Nov 08, 2005 at 15:39 UTC
$rec->vals we can presume is some OO code, but's it's not defined by the OP. What Fletch is doing here is testing the value returned by $rec->val, and according to the result, returning a reference to one of the two arrays. This whole things is wrapped in a @{ } which will deference the array ref returned in the first instance, which he can then push the value to. Here's a slightly less complicated version, using the same principal `use strict; use Data::Dumper; my @numbers = (1,2,3,45,6,76,8,5,7,8); my(@odd, @even); foreach my $number (@numbers) { push @{ is_odd($number) ? \@odd : \@even}, $number; } print Dumper(\@odd, \@even); sub is_odd {$_[0] % 2}` [download] --- my name's not Keith, and I'm not reasonable.	[reply] [d/l]
Re^3: Splitting array into two with a regex by ikegami (Patriarch) on Nov 08, 2005 at 16:01 UTC
Could you explain what does it mean @{$rec->vals}. `@{$rec->vals}` can be written as `@{$rec->vals()}` or as `my $aref = $rec->vals();` `@{$aref}` Is it array ref? `$rec->vals()` is an expression that returns an array reference. `@{$rec->vals()}` is an expression that returns an array lvalue (which means it can be used like a real array). Update: Fixed problem noted by merlyn.	[reply] [d/l] [select]
Re^4: Splitting array into two with a regex by merlyn (Sage) on Nov 08, 2005 at 18:12 UTC
Re^5: Splitting array into two with a regex by ikegami (Patriarch) on Nov 08, 2005 at 19:17 UTC
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Re: Splitting array into two with a regex by dragonchild (Archbishop) on Nov 08, 2005 at 14:46 UTC
This is what Ruby's Array.partition() is for. You can replicate it in Perl pretty easily. `sub partition (&@) { my ($condition, @array) = @_; my (@true, @false); foreach (@array) { if ( $condition->($_) ) { push @true, $_; } else { push @false, $_; } } return \@true, \@false; } my ($ok, $no) = partition { $_[0]->name =~ m/[0-9]{2}$/ } @{ $rec->val +s };` [download] My criteria for good software: Does it work? Can someone else come in, make a change, and be reasonably certain no bugs were introduced?	[reply] [d/l]
Re^2: Splitting array into two with a regex by Tanktalus (Canon) on Nov 08, 2005 at 15:10 UTC
If you're going to replicate it, can you at least make it idiomatically perl? ;-) You have the desired test value in $_ already (good!), but then you go and ruin it by passing it in. Why not just: `sub partition (&@) { my ($condition, @array) = @_; my (@true, @false); foreach (@array) { if ( $condition->() ) { push @true, $_; } else { push @false, $_; } } return \@true, \@false; } my ($ok, $no) = partition { $_->name =~ m/[0-9]{2}$/ } @{ $rec->vals } +;` [download] In what is likely to be a common case, where the array is an array of strings rather than object references, that partition block becomes even more trivial. I've taken to this idiom in the last few months just because of the way it simplifies the callbacks. That it is probably faster (no parameters to pass around) actually has had no bearing on whether I use this or not (may shave off a second or two over three hours - not a concern).	[reply] [d/l]
Re^3: Splitting array into two with a regex by jdporter (Paladin) on Nov 08, 2005 at 16:00 UTC
To generalize it even further: `sub partition (&$@) { my $condition = shift; my $receivers_ar = shift; push @{ $receivers_ar->[ &$condition ] }, $_ for @_; @$receivers_ar } # Example 1: my( @good, @bad ); partition { /u/ ? 1 : 0 } [ \@good, \@bad ], qw( foo bar quux ); print "good=@good\n"; print "bad=@bad\n"; # Example 2: my @r = partition { $_ % 3 } [ [], [], [], ], 0 .. 12; for my $i ( 0 .. $#r ) { print "$i = @{$r[$i]}\n"; }` [download] We're building the house of the future together.	[reply] [d/l]
Re^4: Splitting array into two with a regex by dragonchild (Archbishop) on Nov 08, 2005 at 17:58 UTC
Re^4: Splitting array into two with a regex by Roy Johnson (Monsignor) on Nov 08, 2005 at 16:33 UTC
Re: Splitting array into two with a regex by Roy Johnson (Monsignor) on Nov 08, 2005 at 15:54 UTC
Another Way To Do It, with a single grep (and a little trick): `my @no; my @ok = grep { $_->name =~ m/[0-9][0-9]$/ or !push(@no, $_) }@{ $rec- +>vals };` [download] Caution: Contents may have been coded under pressure.	[reply] [d/l]
Re^2: Splitting array into two with a regex by reasonablekeith (Deacon) on Nov 08, 2005 at 16:12 UTC
well, if you're going to do that, you might as well stick it on one line... `my (@ok, @no) = grep { $_->name =~ m/[0-9][0-9]$/ or !push(@no, $_) }@ +{ $rec->vals };` [download] ... hmmmm, perhaps not :) Update: Definitely not. As Roy Johnson kindly pointed out, @no will not exist in time to be pushed to in the grep. --- my name's not Keith, and I'm not reasonable.	[reply] [d/l]
Re: Splitting array into two with a regex by GrandFather (Saint) on Nov 08, 2005 at 20:24 UTC
And the benchmark: Read more... Benchmark code (3 kB) Prints: Read more... Validation check (416 Bytes) `Rate Tanktalus OP JDPorter Roy Fletch + GF Tanktalus 39861/s -- -14% -23% -43% -44% + -57% OP 46391/s 16% -- -11% -34% -35% + -50% JDPorter 51919/s 30% 12% -- -26% -27% + -44% Roy 70510/s 77% 52% 36% -- -1% + -23% Fletch 71157/s 79% 53% 37% 1% -- + -23% GF 91995/s 131% 98% 77% 30% 29% + --` [download] Update: forgot Roy Johnston's version Perl is Huffman encoded by design.	[reply] [d/l] [select]
Re: Splitting array into two with a regex by blahblahblah (Priest) on Nov 09, 2005 at 00:26 UTC
There's a module on CPAN that does this in a general way, even letting you split the list into more than two result lists: List::Part. -Joe	[reply]
Re: Splitting array into two with a regex by GrandFather (Saint) on Nov 08, 2005 at 19:53 UTC
Another way: `(@ok, @no) = ((), ()); map {$_->name =~ /[0-9][0-9]$/ ? push @ok, $_ : push @no, $_} @{$rec-> +vals};` [download] Perl is Huffman encoded by design.	[reply] [d/l]