Inspect the members of a Posix Character Class
5 direct replies — Read more / Contribute
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by NERDVANA
on Jul 29, 2021 at 08:47
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Perl knows about a lot of posix character classes because you can match against them with the regex library. But what if you want to reverse that? I would like to iterate the characters that belong to a named character class, and take advantage of Perl's knowledge rather than building massive lists of my own. I would also like to avoid brute-force solutions like iterating every character and testing each for membership in the set.
Does anyone know if there is a good way to do this? Ideally quick enough to look up random members of the set in log(n) time or better.
Example of a Not-Good way to do this:
my @alpha= grep /[[:alpha:]]/, map chr, 0..0xEFFFF;
return $alpha[rand scalar @alpha];
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list of lists?
7 direct replies — Read more / Contribute
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by guthrie
on Jul 29, 2021 at 00:04
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beginner confusion...
I had a list of values that i iterated over:
my @zips=("52544", "52557", "50428", "50219");
foreach $zip (@zips) { ... }
Now I want more information for each item, so I have this:
my @sites=( ("50049", "city1", "url1"),
("52556", "city2", "url2"),
("50219", "city3", "url3") )
foreach (my $zip, my $name, $my $url) { ... }
which fails. I have tried multiple permutations, but cannot seem to get the iteration over tuples from an array of tuples right.
TIA.
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pack on unpack with same template
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by jjmoka
on Jul 27, 2021 at 18:33
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$$xmlScalar_r = pack('U0C*', unpack('U0C*', SGMLencode_data($$xmlScalar_r)||(defined($$xmlScalar_r) ? $$xmlScalar_r : '') ));
regardless of everything in the end, it is then just something like:
$string = ...
$x = pack('U0C*', unpack('U0C*', $string));
I see nothing different which cannot be done as just
$x = $string #or without even $string, just $x = ...
so it would seem a useless usage of pack and unpack being the template the same.
Are there special cases of any sort (e.g. different environments, architectures)
where the pack/unpack achieve anything different ?
Thanks
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Dealing with nextline of a file
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by jnarayan81
on Jul 27, 2021 at 04:37
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When I tried to read nextline, the pointer in the while loop reads two lines at a time. Is there another creative way to deal with the file's next line?
use strict;
use warnings;
my %store; my $nextline; my $cnt=1;
my $filename = "$ARGV[0]";
open(my $fh, '<:encoding(UTF-8)', $filename) or die "Could not open fi
+le '$filename' $!";
while (my $row = <$fh>) {
chomp $row;
my @tmp = split /\s+/, $row;
$nextline = <$fh>; chomp $nextline;
my @nexttmp = split /\s+/, $nextline;
print "$row\t$cnt\n";
if ($tmp[0] ne $nexttmp[0]) {
$cnt++;
}
print "$nextline\t$cnt\n";
}
close $filename;
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