Re: How can I tell if a number is a power of 2?

in reply to How can I tell if a number is a power of 2?

What is the most efficient way to shift that 1 to the other end so I can compare the value to 1 instead of using this horrible regex. Or is there a quicker way?

I might try table lookup.

sub is_power_of_2 {
      my $n = shift;
      1 == grep { $_ == $n } ( 1 2 4 8 ... )
  }
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Comment on Re: How can I tell if a number is a power of 2? Download Code

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Re: Re: How can I tell if a number is a power of 2? by Cine (Friar) on Jan 29, 2002 at 00:25 UTC
`if n is a power of two, then n = 2^x => lg n = x*lg 2 => lg n/lg 2 = x => lg n = x thus lg n is the power of 2 of your number. But usually only log10 and + natural log is avail, but lg x = log x/ lg e.` [download] T I M T O W T D I Edit by tye to replace PRE to CODE around long line(s)	[reply] [d/l]

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