素数をカンマ区切りで各行10個ずつ出力するプログラム。

prime.pl

#!/opt/local/bin/perl
# 
# 素数をカンマ区切りで各行10個ずつ出力するプログラム。
# 
# 使い方
# $ perl prime.pl {number} [filename]
# 
use strict;
use warnings;
use POSIX;

if (@ARGV == 0 or @ARGV > 2) {
  print "Usage: ${0} {number} [filename]\n";
  exit(0);
}

if (@ARGV == 2) {
  open(HNDL, ">${ARGV[1]}");
} else {
  open(HNDL, ">-");
}

my @list = &create_prime_list($ARGV[0]);

for (my $i = 0; $i < @list; $i++) {
  print HNDL $list[$i];
  if (($i + 1) % 10 == 0) {
    print HNDL "\n";
  } else {
    print HNDL ",";
  }
}

close(HNDL);

sub create_prime_list($) {
  my($length) = @_;
  my @list = (2);
  my $n = 3;
  while (@list < $length) {
    push(@list, $n) if &is_prime_number($n, @list);
    $n += 2;
  }
  return @list;
}

sub is_prime_number($@) {
  my($n, @ps) = @_;
  my $sqrt = floor(sqrt($n));
  my @check_list = grep {$_<=$sqrt} @ps;
  foreach my $c (@check_list) {
    return 0 if ($n % $c == 0);
  }
  return 1;
}