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  Generate first N prime numbers

Recently I am taking an online course named "Startup Engineering" on coursera. There is one assignment which is to use NodeJS to write a program to generate the first 100 prime numbers. This may be very easy for many people. Here I just want to share with you the code to generate not only the first 100 prime numbers. but also any number of prime numbers. Below is the code snippet: //Helper class to generate prime numbers var PrimeProcessor=(function(){ var primeArray=[]; functio...

   Algorithm,Prime number,NodeJS,coursera,JavaScript     2013-06-29 22:08:22

  C Macro Tips and Tricks

Preprocessor vs Compiler To properly understand C macros, you must understand how a C program is compiled. In particular, you must understand the different things that happen in the preprocessor and in the compiler. The preprocessor runs first, as the name implies. It performs some simple textual manipulations, such as: Stripping comments. Resolving #include directives and replacing them with the contents of the included file. Evaluating #if and #ifdef directives. Evaluating #defin...

   C,Macro,Preprocessor,Trick     2012-05-01 06:49:05

  + operation on JavaScript objects

In JavaScript, there are two types of values: primitive and object. Primitives consist undefined, null, boolean, number and string. Other values such as array and function are objects. When applying + operation on different type of values, there would be three kinds of type conversion. Primitive conversion Number conversion String conversion There three type conversions have corresponding abstract operations in JavaScript: ToPrimitive(), ToNumber(), ToString(). For number additi...

   JAVASCRIPT,PROGRAMMING     2018-10-12 22:19:12

  Reducing Code Nesting

"This guy’s code sucks!" It’s something we’ve all said or thought when we run into code we don’t like. Sometimes it’s because it’s buggy, sometimes it’s because it conforms to a style we don’t like, and sometimes it’s because it just feels wrong. Recently I found myself thinking this, and automatically jumping to the conclusion that the developer who wrote it was a novice. The code had a distinct property that I dislike: lots of ...

   Code nesting,Readability,Maintainability,Reduction     2012-01-02 08:13:46

  A trap about PHP random number

The method to get random number in PHP is very simple, we only need to use rand() function. int rand ( int $min , int $max ) One function call can return the random number in a specified range. But in fact, the random number in computer is actually pseudorandomness, generally to increase the randomness, we may set a random seed before calling rand(). void srand ([ int $seed ] ) According to other language features, we should pass a time value as a parameter to the srand() function, generally...

   PHP,rand,srand,mt_rand     2013-06-07 09:10:10

  Video website in big data era

Big data initially means the large data set which is not able to be analyzed, but later it was derivatized to the method to analyze huge amounts of data in  order to gain great value.This is a form which gradually gets attention, It's difficult to analyze these data and it's also difficult to store these data and it needs some unprecedented way, Now in China many companies use the open source Hadoop distributed data cluster to meet the needs of data statistics. Since we can get segmented d...

   Netflix,Big data,Data mining     2013-04-11 04:20:40

  Hexadecimal and long in Java

Today I encountered a hexadecimal operation problem when I was implementing a bit reverse function for integer type. Basically in the implementation, there is an operation which is to do the bit operation & between one long integer and a hexadecimal number 0x00000000FFFFFFFFF. I was expecting that the high 32 bits of the long integer will be zeroed. But unfortunately I didn't get the expected result. The basic implementation is: long num=0x00F0_0000; num = (num>>16) | (num<<16); ...

   Hexadecimal,long,Java,bitwise operation     2014-06-18 23:44:32

  Testing like the TSA

When developers first discover the wonders of test-driven development, it’s like gaining entrance to a new and better world with less stress and insecurity. It truly is a wonderful experience well worth celebrating. But internalizing the benefits of testing is only the first step to enlightenment. Knowing what not to test is the harder part of the lesson. While as a beginner you shouldn’t worry much about what not to test on day one, you better start picking it up by day t...

   Testing,QA,TSA     2012-04-11 13:41:19

  Examples of bad design

Good designs always help users solve their problems in a convenient and familiar way. It takes little or no time for users getting used to the product with a good design. In contrast, bad designs frequently introduce confusion and complexity to users. Before we design any product, we should think carefully about every aspect of the product. We share some really bad design here to show how they can affect people's life. 1. USB Connector Have you ever put one in right on the first try? We frequen...

   Bad design,Usability,Web design     2013-09-25 22:57:49

  Optimization Tricks used by the Lockless Memory Allocator

With the releasing of the Lockless Memory Allocator under the GPL version 3.0 license, we can now discuss more of the optimization tricks used inside it. Many of these are things you wouldn't want to use in normal code. However, when speed is the ultimate goal, sometimes we need to break a few rules and use code that is a little sneaky.The SlabA slab is a well-known technique for allocating fixed size objects. For a given object size, a chunk of memory is divided up into smaller regions of that ...

   Optimization,Memory allocation     2011-11-16 08:02:16

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