in reply to Re: Challenge: Another Infinite Lazy List

in thread Challenge: Another Infinite Lazy List

If you want a pure iterative solution, you could compute a factor wheel and print everything but the usual trial divisors. The code looks messier, but it requires no mod calculations in the loop, just adds. I computed the wheel using Math::Big::Factors (so for people following the original articles, we have come full circle...).

use strict; sub limit_print { my ($count,@lst) = @_; return if $count <= 0; if (@lst <= $count) { print join(" ",@lst,""); } else { print join(" ",@lst[0..$count-1],""); } } # factor wheel for 2,3,5 my @add = (2,2,4,2,4,2,4,6,2,6,4,2,4,2,4,6,2); # wheel restart point. my $ws = 9; my $we = scalar @add - 1; my @lst = (2,3,4,5); my $count = $ARGV[0]; limit_print($count, @lst); $count -= @lst; if ($count <= 0) { print "\n" if $count > -4; exit(0); } my $lastskip = 5; my $place = 6; my $w = 1; while ($count > 0) { # find the next nonmultiple of 2,3, and 5. my $nextskip = $lastskip + $add[$w]; my @lst = ($place..$nextskip-1); limit_print($count, @lst); $count -= @lst; $place = $nextskip+1; $lastskip = $nextskip; $w = $ws if $w++ == $we; } print "\n";

In Section
Seekers of Perl Wisdom