Can split split against more than one character in a string of the same character?

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

Using Padre's Regex Editor today, very nice tool. I thought I might be able to split a pattern on a string of the same character, but that didn't seem to want to play. I could use something like unpack, but wondered if there were any tricks to doing this using split?

my @splitted = split /(?:(?=a{2})(?<=a{2}))/, 'aaaaaaaaa';
print join " ", @splitted;
output recieved :aa a a a a a aa
output desired  :aa aa aa aa a
[download]

The main issue is that at each position there is a match, so the string is split at every position. I tried a mix of assertions and literals but the best I got was to match two at the start and end with single entities in between

I have a solution with s/// that I am happy about. I'm getting a count and any remainders modulo the length of the test string remain in the string. If I need to I can write a while loop rather than a map, though this is probably already better for what I want.

my $prim_to_test = ${ num_to_nat(2) }[0]; #get_wildmarks(); 'aa'

my $split_pattern =  qr/(\Q$prim_to_test\E)/;

print "split_pat: $split_pattern\n";

my @splitted = map
"$_ x $1", ( $wildmarks =~ s/(?=$split_pattern)$split_pattern//g );

print "splitted: ", join " \N{U+68} ", @splitted, "r: $wildmarks";

output:splitted: 4 x aa h r: a
[download]

But can split do it?

SPoiler ALert: Yes.

Further, it would appear the ability to use arbitrary characters is also expanded

Comment on Can split split against more than one character in a string of the same character? Select or Download Code

Replies are listed 'Best First'.
Re: Can split split against more than one character in a string of the same character? by johngg (Canon) on Jul 15, 2019 at 22:12 UTC
Another approach would be to use unpack. `johngg@shiraz:~/perl/Monks$ perl -Mstrict -Mwarnings -E ' my $str = q{aaaaaaaaa}; my @parts = unpack q{(a2)*}, $str; say qq{@parts};' aa aa aa aa a` [download] I hope this is helpful. Cheers, JohnGG	[reply] [d/l]
Re^2: Can split split against more than one character in a string of the same character? by Don Coyote (Hermit) on Jul 15, 2019 at 22:35 UTC
That looks fast!	[reply]
Re: Can split split against more than one character in a string of the same character? by holli (Abbot) on Jul 15, 2019 at 20:52 UTC
`split` returns the separators when there are captures in the separator regex. So you can simply do `D:\ENV>perl -e "$x = qq#aaaaaaa#; print join '#', split /(..)/, $x" #aa##aa##aa#a` [download] and grep away the empty elements. holli You can lead your users to water, but alas, you cannot drown them.	[reply] [d/l] [select]
Re^2: Can split split against more than one character in a string of the same character? by Don Coyote (Hermit) on Jul 15, 2019 at 22:23 UTC
Ah, I did think about placing dots in the backward assertion for a brief moment, but even that is ott. I can just split into an array and join that on print. Thanks	[reply]
Re: Can split split against more than one character in a string of the same character? by hippo (Archbishop) on Jul 15, 2019 at 21:17 UTC
No need to mess with split when you just want to divide up a string of the same chars: `use strict; use warnings; use Test::More tests => 1; my $in = 'aaaaaaaaa'; my $want = 'aa aa aa aa a'; my $have = join ' ', ($in =~ /a{1,2}/g); is $have, $want;` [download]	[reply] [d/l]
Re^2: Can split split against more than one character in a string of the same character? by Don Coyote (Hermit) on Jul 15, 2019 at 22:29 UTC
I had an inkling that split could do this, but was approaching it from too complicated a place. Starting to get the feeling I should have `perldoc -f split` now. This is a clean and efficient way of doing this with match though, thanks I like the simplicity of the test structure, allowing for documenting attempts. That's really great.	[reply] [d/l]