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Re: Re (tilly) 1: Power of two round up.

by japhy (Canon)
on Dec 15, 2000 at 23:31 UTC ( #46896=note: print w/ replies, xml ) Need Help??

in reply to Re (tilly) 1: Power of two round up.
in thread Power of two round up.

And an even faster WTDI:
sub next_pwr { my ($x,$p) = (@_,2); # default to next_pwr(X,2) my $log = log($x)/log($p); $log = int($log+1) if $log != int($log); return $p**$log; }
You can even add a log() memoization in there:
{ my %LOG = (2 => log(2)); # most common sub next_pwr { my ($x,$p) = (@_,2); # default to next_pwr(X,2) # assertions, etc. die "illegal base: $p" if $p < 2; return 1 if $x == 1; $p = int $p; my $log = ($LOG{$x} ||= log($x)) / ($LOG{$p} ||= log($p)); $log = int($log+1) if $log != int($log); return $p ** $log; } }

japhy -- Perl and Regex Hacker

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