#!perl -w

use strict;
no strict "vars";

use Set::IntegerFast;

print "\n***** Calculating Prime Numbers - The Seave Of Erathostenes *****\n";

$limit = 0;

if (-t STDIN)
{
    while ($limit < 16)
    {
        print "\nPlease enter an upper limit (>15): ";
        $limit = <STDIN>;
        chop($limit) while ($limit =~ /\n$/);
        $limit = 0 if (($limit eq "") || ($limit =~ /\D/));
    }
    print "\n";
}
else
{
    $limit = 100;
    print "\nRunning in batch mode - using $limit as upper limit.\n\n";
}

$set = Set::IntegerFast::Create($limit+1);

$set->Fill;

$set->Delete(0);
$set->Delete(1);

print "Calculating the prime numbers in the range [2..$limit]...\n\n";

$start = time;

for ( $j = 4; $j <= $limit; $j += 2 )
{
    $set->Delete($j);
}

for ( $i = 3; ($j = $i * $i) <= $limit; $i += 2 )
{
    for ( ; $j <= $limit; $j += $i )
    {
        $set->Delete($j);
    }
}

$stop = time;

&print_elapsed_time;

$min = $set->Min;
$max = $set->Max;
$norm = $set->Norm;

print "Found $norm prime numbers in the range [2..$limit]:\n\n";

for ( $i = $min, $j = 0; $i <= $max; $i++ )
{
    if ($set->in($i))
    {
        print "prime number #", ++$j, " = $i\n";
    }
}

print "\n";

$set->Destroy;

exit;

sub print_elapsed_time
{
    ($sec,$min,$hour,$year,$yday) = (gmtime($stop - $start))[0,1,2,5,7];
    $year -= 70;
    $flag = 0;
    print "Elapsed time: ";
    if ($year > 0)
    {
        printf("%d year%s ", $year, ($year!=1)?"s":"");
        $flag = 1;
    }
    if (($yday > 0) || $flag)
    {
        printf("%d day%s ", $yday, ($yday!=1)?"s":"");
        $flag = 1;
    }
    if (($hour > 0) || $flag)
    {
        printf("%d hour%s ", $hour, ($hour!=1)?"s":"");
        $flag = 1;
    }
    if (($min > 0) || $flag)
    {
        printf("%d minute%s ", $min, ($min!=1)?"s":"");
    }
    printf("%d second%s.\n\n", $sec, ($sec!=1)?"s":"");
}

__END__
