Comments on: How to Check If a Number Is a Power of Two http://www.exploringbinary.com/how-to-check-if-a-number-is-a-power-of-two/ Binary Numbers, Binary Code, and Binary Logic Mon, 30 Jan 2012 01:37:52 +0000 hourly 1 http://wordpress.org/?v=3.2.1 By: Big Eclipse http://www.exploringbinary.com/how-to-check-if-a-number-is-a-power-of-two/comment-page-1/#comment-4861 Big Eclipse Wed, 16 Feb 2011 22:01:38 +0000 http://www.exploringbinary.com/?p=78#comment-4861 Great article. Love the Q & A at the end. Great article. Love the Q & A at the end.

]]> By: Rick Regan http://www.exploringbinary.com/how-to-check-if-a-number-is-a-power-of-two/comment-page-1/#comment-80 Rick Regan Thu, 04 Dec 2008 01:12:53 +0000 http://www.exploringbinary.com/?p=78#comment-80 Matt, that's correct, and probably the easiest thing to do if you have a computer or scientific calculator on hand. Note also, at least for positive integers, you could compute the prime factorization and check if all factors are 2 (if they are, the number is a power of two). If you have a computer, you could also check -- if the number is a positive integer -- how many 1 bits are set (one 1 bit means the number is a power of two). But my goal for this article was to explore the nature of the powers of two, by making you suffer through "pencil and paper" arithmetic ;) . (I added a paragraph to the introduction to make that clear). <em>Update:</em> As for using logarithms in computer programs, beware that they may not come out exactly as integers for powers of two. This is due to how floating-point works. See <a href="http://www.exploringbinary.com/ten-ways-to-check-if-an-integer-is-a-power-of-two-in-c/" title="Read Article “Ten Ways to Check if an Integer Is a Power Of Two in C”" rel="nofollow">``Ten Ways to Check if an Integer Is a Power Of Two in C''</a> for more info. Matt, that’s correct, and probably the easiest thing to do if you have a computer or scientific calculator on hand. Note also, at least for positive integers, you could compute the prime factorization and check if all factors are 2 (if they are, the number is a power of two). If you have a computer, you could also check — if the number is a positive integer — how many 1 bits are set (one 1 bit means the number is a power of two).

But my goal for this article was to explore the nature of the powers of two, by making you suffer through “pencil and paper” arithmetic ;) . (I added a paragraph to the introduction to make that clear).

Update: As for using logarithms in computer programs, beware that they may not come out exactly as integers for powers of two. This is due to how floating-point works. See “Ten Ways to Check if an Integer Is a Power Of Two in C” for more info.

]]> By: Matt C http://www.exploringbinary.com/how-to-check-if-a-number-is-a-power-of-two/comment-page-1/#comment-79 Matt C Wed, 03 Dec 2008 23:21:13 +0000 http://www.exploringbinary.com/?p=78#comment-79 You can take the log(base 2), or (log x / log 2) of a number and if its a integer value then its a power of 2. You can take the log(base 2), or (log x / log 2) of a number and if its a integer value then its a power of 2.

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