Obviously no mathematicians in the house :) 
sub is_power_of_2 {
  return 0 unless $_[0]>0; # to avoid log error
  log($_[0])/log(2) - int(log($_[0])/log(2)) ? 0 : 1 
}

[download]
cLive ;-)

Update: - Cine (not linked because of very irritating JS on home node) proves me wrong while I'm typing up :)

Update: - Damn you tye... This falls down as far as computing accuracy goes for 2 to the power of 29, 31, 39, 47 and probably a few more. Where's that posix math module when you need it :)

Ah well, here's another: 

sub is_power_of_2 {
  local $_ = $_[0];
  $_/=2 while ($_ > 1);
  return if ($_ - int($_));
  1;
}

[download]

In reply to Re: How can I tell if a number is a power of 2? by cLive ;-)
in thread How can I tell if a number is a power of 2? by larryk

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