c - How does this bitwise operation check for a power of 2? -

-

I'm looking at some code that should be trivial - but my math has failed me badly here.

Here is a situation that examines a number if someone uses the following 2 using the following: 

  if ((num! = 1) & Amp; (num & amp; num - 1) My question is, how does a bit wise use and determines between num and num - 1 if 2 is the power of number 2?

2 Any power of zero 1 is all: ( 2 N - 1 = 111 .... b ) 

  2 = 2 ^ 1 2-1 = 1 (1b) 4 = 2 ^ 2 4-1 = 3 (11b) 8 = 2 ^ 3 8-1 = 7 (111b) For example, take 8, 1000 & amp; 0111 = 0000 
 
 so if expression test is not the power of any number 2.

Comments

Post a Comment

Popular posts from this blog

c++ - Linux and clipboard -

-
After selecting the copies of the buffer in Linux, after the text, we can click and paste the button between the mouse. I think there is a special buffer for this, I want to use it. Programming Language: C ++ Your Library: Qt Thanks. There is just one more correct answer than Paul Dixon, which answers your needs: / P > QClipboard * clipboard = QApplication :: clipboard (); CastString Selected Text = Clipboard-> Text (QClipboard :: Selection);
Read more

What is expire header and how to achive them in ASP.NET and PHP? -

-
I have examined the performance statistics of my website today. I have received a warning (or error may occur) that is given below Add Terminal Headers Here are 15 static components without a 15-futures end date * (no end) Http://www.example.com/video/css/global.css * (no time limit) http://www.example.com/video/js/global.js * (no expiration ) Http: //www.example.com/video/images/main-bg.png what it means and how to achieve it both in PHP and ASP.Net. I am on a shared hosting server, so please tell me some ways to use the code, because I can not make any modifications at the end of the server. If I expire the header, then there is no chance that if I make changes to the CSS, then the user will not be able to remove them immediately because CSS and other files have a fixed time limit (1 month, week ) Are cached for. Is Is there any harm to using PHP? $ time = time () + 3 * 24 * 60 * 60; // 3 day headings ('End:'. GMDAT ('D, D MYH: i: s \ g \ m \ t',
Read more

sql server - How can I determine which of my SQL 2005 statistics are unused? -

-
After a few years, one of my biggest databases has deposited 73 figures out of its largest tables. With Indexes, I can run many types of reports and queries, how often / heavily specific indexes are used. What is an equivalent for data? We are running SQL 2005. To make statistics automatically managed and honest, I would like to "update statistics", "create statistics" and There is no information about any management except "drop statistics" orders. In theory, UPDATE should handle the addition and removal of statistical data. In addition, I've never heard about the amount of storage or storage taking in large amounts, so I'm not sure whether there is any reason for the alarm or not. If you are seeing a potential problem, then I would suggest running an update before, if it does not clean it, it is leaving and then it appears to be safe operation (because it is the only query optimizer Is for). I will not leave "left" in the
Read more