Re: Prime Number Finder

[Anonymous Monk]

Straight from 'perlthrtut' of 5.18. Just throw two numbers at it: perl primes.pl 2 100

#!/usr/bin/perl
use strict;
use warnings;

use threads;
use Thread::Queue;

sub check_num {
    my ($upstream, $cur_prime) = @_;
    my $kid;
    my $downstream = Thread::Queue->new();

    while (my $num = $upstream->dequeue()) {
        next unless ($num % $cur_prime);

        if ($kid) {
            $downstream->enqueue($num);
        } else {
            print("Found prime: $num\n");
            $kid = threads->create(\&check_num, $downstream, $num);
        }
    }

    if ($kid) {
        $downstream->enqueue(undef);
        $kid->join();
    }
}

my $stream = Thread::Queue->new(shift()..shift(), undef);
check_num($stream, 2);

[Anonymous Monk]

TMTOWTDI :-)

#!/usr/bin/perl
s;;
;x;
while() { print if (1 x++ $\) !~ m }
{
   $|^(..+)\1+$|^$\$}
}

[lonewolf28]

Can you please explain you code? I'm a noob, honestly i didn't understand your code but it works fine.

[Anonymous Monk]

Managed utilize it, but I kinda butchered it. Yeah you can still use Math::Prime::Util.

But I do not know how exactly it work. It does some magic with the output line separator.

That if structure is hideous.

sub primes($end)
{  
    open my $FH, '>', \my $output or die "Cannot open filehandle: $!";
    
    $output = "";
    $\      = 1;

    while($\ < $end) 
    { 
        $_ = "";    

        print  $FH $_."\n"      if( (1 x++ $\)  !~ m/  {$  |   ^(..+)\
+1+$   |     ^\\\$\\$    }/x );
    }
    close($FH);
    
    my @primeNumbers = split("\n", $output);
    shift @primeNumbers;       # a blank element will get through

    return \@primeNumbers;
}