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  Why 0.1+0.2 != 0.3

In programming languages such as JavaScript, c/c++, Java and Matlab, you will find that you will get unexpected result when doing float point calculation. For example, when calculating 0.1 + 0.1, you will not get 0.3: > 0.1 + 0.2 == 0.3 false > 0.1 + 0.2 0.30000000000000004 Don't be surprised of this result, this is the end result of IEEE 754 standard, float point number cannot be accurately represented according to IEEE 754 because: No enough memory is allocated for representing the num...

   float point,comparison,JavaScript     2014-11-19 05:32:46

  Recover deleted file in Linux EXT3 file system

Environment : CentOS 5.3 x86_64, /dev/sdb1 is the data segment /data0. EXT3 file system. Problem : /data0/tcsql/cankao/phpcws-1.5.0/httpcws.cpp is deleted mistakenly and httpcws.cpp is not backed up. It will take much time to rewrite this program again. So we must recover it back. debugfs is feasible in EXT2 file system, but in EXT3 file system, it's not very useful. There is one open source software called ext3grep which can help us recover deleted file in EXT3 file system. The recovery steps a...

   Linux,EXT3,File recovery     2013-08-16 07:06:45

  Magic CSS shape

There is a question on StackOverflow which states that someone finds a CSS sample on http://css-tricks.com/examples/ShapesOfCSS/  , the sample shows a triangle created with pure CSS. The source code is :#triangle-up {width: 0;height: 0;border-left: 50px solid transparent;border-right: 50px solid transparent;border-bottom: 100px solid red;}The question is how these few lines can create a triangle? Next we give the answer and the detail illustration to this question We need to consider the B...

   CSS,Triangle,Box model,Border     2012-04-20 12:56:22

  TIOBE: PHP is coming back

TIOBE released the programming language index for July 2013. The highlight of this month is that PHP is coming back. It ranks the fifth and has an increase of 1.54% compared to January. There are no changes in the ranking for the top 4 languages. The reason why PHP is back may be attributed to the new PHP Zend Framework that was released in September 2012, but this reason is not very convincing. PositionJul 2013PositionJul 2012Delta in PositionProgramming LanguageRatingsJul 2013Delta Jul...

   TIOBE,PHP,Zend framework,July     2013-07-09 05:22:50

  Launch Java process programmatically in Java

In some cases while working on some automation testcase, developers would like to launch Java process programmatically so that the tests can be ran without manual intervention. Java provides such methods to achieve this. ProcessBuilder can be used to build a Java process which can be launched when everything is ready. Basically it can take a list of parameters which are similar to the command line options/arguments.  For example, if you want to launch a Java process, you can do followi...

   JAVA,PROCESSBUILDER,COMMAND LINE     2016-04-27 04:03:30

  Handy PHP functions should be in your toolkit

When developing projects, there are always some common work should be accomplished, for example, encrption/decryption, get IP. As a PHP developer, you should have a list of the handy functions in your toolkit so that you can pick up in every project you work on. Here is a summary of some handy PHP functions. 1. PHP encryption/decryption Encryption/decryption can be used when storing user confidential information such as passwords. Below function uses base64 and MD5 to accomplish encryption/decry...

   PHP,function,real IP,SQL injection     2014-12-06 08:46:08

  Interview Programming Problems Done Right

Introduction Why 37signals Doesn't Hire Programmers Based on Brainteasers and my comment on HN generated a lot of responses, so much so that I'm writing this post to properly explain the essence of a good (IMHO) interview programming problem. Pascal's Triangle Pascal's Triangle is a shortcut for getting coefficients most often used binomial probability. The root element is 1. Every other element is the sum of the one or two above it (diagonally left and diagonally right). There are severa...

   Interview,Programming problem,Pascal,Triangle     2012-01-06 09:46:43

  Programming is a Super Power

In a society where technology and the Internet have become incredibly prominent elements of our daily lives, being able to program is akin to having a super power. In fact, a programmer is able to not only easily interact with cutting edge technology, but also to take advantage of said technology to transform pure thoughts into something as tangible and useful as software.I would argue that there has never been a more exciting time for being able to program. While being a part of our industry ba...

   Programming,Programmer,Super power     2011-04-01 00:12:13

  Using Java keytool programmatically

Java provides a command line tool to access and operate different keystore which store keys and certificates. This tool is named keytool and is located at \bin.  On command line, you can issue below command to generate a keystore named mytest.jks which contains a private key and certificate chain. keytool -genkeypair -alias mykey -keyalg RSA -sigalg SHA256withRSA -dname CN=Java -storetype JKS -keypass password -keystore mytest.jks -storepass password Sometimes, in testing purpose, w...

   JAVA,KEYTOOL     2016-01-09 06:28:07

  A Python assignment trap

Python has no assignment, it only has reference. Assume, we have following code snippet: >>> values = [0, 1, 2] >>> values[1] = values >>> values [0, [...], 2] Why the result is not [0, [0, 1, 2], 2], instead it goes into an infinite loop? To understand this, we need to understand some basics about Python. Python has no variables, it only has labels. When we run: values = [0, 1, 2] Python will first create a list object [0,1,2], then it labels it as values. If we later...

   Python,Assignment,Trap,Shallow copy     2013-07-19 22:08:36

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