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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

  Accurate floating point number calculation in JavaScript

In JavaScript, since floating point is defined with IEEE754,there will be some accuracy issues while doing floating point number arithmetic. Here is a function which can resolve the accuracy issue. var calc = function(num1,operator,num2,len){    var numFixs = function(num){        var arr = num.toFixed(len).toString().split('.');        return parseInt(arr.join(''));    }    switch(operator){...

   JavaScript, floating point,IEEE 754,accuracy     2012-12-27 11:07:49

  How regular expression works

Rob Pike wrote 30 lines of codes to realize a simple regular expression matcher in his book The practice of Programming. This piece of code is really cool. Let's take a look at the code.Meaning of different characters.Character Meaning c General character . Match any single character ^ Match start of a string $ Match end of a string * Match zero or many occurrences of a character /*match ：Test the regexp in text*/int match(char* regexp,char* text){    if(regexp[0] == '^')&n...

   Regular expression,Implementation,Rob Pike,C     2012-06-25 05:23:41

  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

  Name resolution order in JavaScript

To understand what value a variable has in JavaScript, we need to understand some concepts such as scope and name resolution order. JavaScript has two scopes; one is program level and the other one is function level. Unlike in C,C++ or Java, JavaScript has no block level scope. So a variable defined in a if block will still be available outside. For example, the below example: var foo = 1; function bar() { if (true) { var foo = 10; } alert(foo); } bar(); The alert will display 10 since the ...

   JavaScript,Scope,Name resolution     2013-07-10 01:29:28

  Carriage return and line feed

In programming and document editing, we may frequently encounter carriage return and line feed, i.e the well known CRLF.  But do you know about the history and difference of carriage return and line feed? Before computer came out, there was a type of teleprinter called Teletype Model 33. It can print 10 characters each second. But there is one problem with this, after finishing printing each line, it will take 0.2 second to move to next line, which is time of printing 2 characters. If a new...

   CR,CARRIAGE RETURN,LINE FEED,LF,NEW LINE,CRLF     2017-02-19 08:29:23

  try { return } finally {}

Do you know what value will be printed when following program is ran? class Test { public int aaa() { int x = 1; try { return ++x; } catch (Exception e) { } finally { ++x; } return x; } public static void main(String[] args) { Test t = new Test(); int y = t.aaa(); System.out.println(y); } } And before answering the above question, do you have answers to following questions? If ther...

   JAVA,JAVA INTERVIEW QUESTION     2016-09-26 08:06:28

  Google CEO Sundar Pichai : Google is open to return to China

At the Code Conference on Wednesday, Google CEO Sundar Pichai expressed his thought on Google's position in China. He expressed the openness of Google to return to China. "Google is in China....But Google Search is not there in China...But personally for me, I care about serving users globally in every corner. I always thought Google is for everyone, that applies to China, too. So wherever possible, we want to be in China to serve Chinese users....If we do it in a right and thoug...

   GOOGLE,CHINA,SUNDAR PICHAI,CODE CONFERENCE     2016-06-02 01:09:21

  Implementing DESede/ECB/NoPadding cipher algorithm in GoLang

By default, GoLang doesn't provide the ECB mode cipher for DESede though there is CBC mode provided. In cases we need to encrypt/decrypt data with ECB mode, we need to implement those by ourselves. This mode is frequently used when encrypting/decrypting PIN block which is small block data less than 16 bytes. In this post, we will introduce how to implement the DESede/ECB/NoPadding algorithm in GoLang by using the existing cipher support. Here we will not cover how DESede works in detail, instead...

   SECURITY,SAMPLE,GOLANG,DES,DESEDE,3DES     2019-07-29 06:43:50

  C++ : string beginWith and endWith

C++ is an very powerful programming language. It is efficient and flexible. When writing C++ programs, we may often need to process strings and often we need to check whether a string begin with some substring or end with some substring. We can use following functions to ahieve these:     static bool beginWith(const std::string str,const std::string needle){        return (!str.compare(0,needle.length(),needle));    }    ...

   C++,beginWith,endWith,     2012-08-31 06:53:44

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