Re^2: Uninitialized warnings trouble

Fun little problem. Here's another entry in my "The only data structure needed is a multi-line string" collection.

#!/usr/bin/perl

use strict; # https://perlmonks.org/?node_id=11148831
use warnings;

sub quarterturn
  {
  my $new = '';
  $new .= "\n" while s/.$/ $new .= $&; '' /gem;
  return $new;
  }

my $forest = do { local (@ARGV, $/) = 'input8.txt'; <> };
my $visible = '';

for ( 0 .. 3 )
  {
  $visible |= $forest =~ s{(.)(?=(.*))}{ $2 =~ /[$1-9]/ ^ 1 }ger;
  $_ = quarterturn for $forest, $visible;
  }

my $totalvisible = $visible =~ tr/1//; # count ones
print "$forest\n$visible\ntotal visible: $totalvisible\n";
[download]

Comment on Re^2: Uninitialized warnings trouble Download Code

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Re^3: Uninitialized warnings trouble by rsFalse (Chaplain) on Dec 14, 2022 at 22:53 UTC
Nice code of yours! I will share an alternative to your regex, which is longer and uses `(?{ ... })`, but avoids repeated lookahead: `for ( 0 .. 3 ) { my $max; $visible \|= $forest =~ s { ^ (?{ $max = -1; }) (*FAIL) \| (\d) } { length( $1 > $max and $max = $1 ) }germx; $_ = quarterturn for $forest, $visible; }` [download]	[reply] [d/l] [select]
Re^3: Uninitialized warnings trouble by jwkrahn (Abbot) on Dec 14, 2022 at 07:45 UTC
`$new .= "\n" while s/.$/ $new .= $&; '' /gem;` [download] Did you test this? `$ time perl -e' use Data::Dumper; $Data::Dumper::Useqq = 1; my $x = "123456789\n"; print Dumper $x; my $new = ""; $new .= "\n" while $x =~ s/.$/ $new .= $&; '' /gem; print Dumper $new; ' $VAR1 = "123456789\n"; Out of memory! real 1m54.230s user 0m3.216s sys 0m9.332s` [download] BTW, my system has 32GB of RAM ouch! Sorry, my mistake was leaving in the single quotes, oops.	[reply] [d/l] [select]