Stuart White wrote:
> So I figured out from folks on the list, Beginning
> Perl, and some print statements that
> @list = (2 .. $input);
>
> puts the range of numbers into an array, and that if I
> stringified it, then it would put the entire range
> into $list[0]
>
> Now that I've figured that bit out, I went on to
> remove all the even numbers from the list. I got that
> done with this:
> foreach (@list)
> {
> if ($_ % 2 != 0)
> {
> unshift(@primelist, $_);
> @primelist\n";
> }
> }
>
> Now what I'd like to do to test whether or not I have
> a prime number is to get at each element in
> @primelist, and use the modulus operator on each
> element against each element in @list. For example:
> $primelist[0] % $list[0]
> $primelist[0] % $list[1]
> $primelist[0] % $list[2]
> $primelist[1] % $list[0]
> $primelist[1] % $list[1]
> $primelist[1] % $list[2]
> $primelist[2] % $list[0]
> $primelist[2] % $list[1]
> $primelist[2] % $list[2]
>
> and if the result doesn't equal 0 for every test
> except for against itself, then I want to unshift it
> onto @primelist.
>
> I thought I'd do this with nested foreach loops, but
> that didn't seem to work. Any ideas?
> Thanks.
>
> oops, here's my code:
>
> #!/usr/bin/perl
> # primeNumbers.pl
> use warnings;
> use strict;
> my $input;
> my @list;
> my @primelist;
> print "I want you to enter a list of numbers bigger
> than 2.\n";
> print "To mark the end of your list, enter 0.\n";
> print "Enter a number that is bigger than 2:\t";
> $input = <STDIN>;
> chomp($input);
> print "This is your number: $input \n";
> @list = (2 .. $input);
>
> print "this is this the fourth element, but has an
> index of 3: $list[3]\n";
> foreach (@list)
> {
> if ($_ % 2 != 0)
> {
> unshift(@primelist, $_);
> print "this is the inner loop of primelist:
> @primelist\n";
> }
> }
> print "this is the outer loop of primelist:
> @primelist\n";
You must b getting bored and tense with all that code and numbers and stuff.
Take a break, and enjoy some rolling screen graphics:
my @primes = (2);
my $candidate = 3;
while(1) {
my $limit = $candidate ** 0.5;
my $has_factor = 0;
foreach (@primes) {
if ($_ > $limit) {
push @primes, $candidate;
last;
}
unless ($candidate % $_) {
$has_factor = 1;
last;
}
}
unless ($has_factor) {
print "$_ " foreach @primes;
print "\n";
}
$candidate++;
}
Joseph
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