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  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

  When and How to Use the Go Channel

Go’s concise structure and powerful native library enable us to hit the ground running easily. It is more efficient than Java or Python when implementing the same functions, especially its concurrent programming, which is very handy and widely admired due to its goroutine and channel. goroutine and channel has much to dig into, and let’s start with channel, which I used to consider narrowly as a message queue to transfer data between gorouti...

   GOLANG,CONTEXT,CHANNEL     2022-09-17 23:06:36

  Programming Language Readability

Lets compare some Python to Haskell for solving the same problem.  The problem we’ll pick is Trie data-structure for auto-completions.  We are interested not so much in the nitty gritty of the algorithm, but in the language style itself.  Auto-complete has been in the programming news a lot recently; both a Python and a Haskell solver have turned up. (I suspect this post got flagged on Hacker News :(  It never got on the front-page despite the rapid upvoting on a n...

   Programming,Readability,Python,Haskell     2012-02-27 04:52:02

  Understanding an interesting JavaScript map function question

With the evolvement of JavaScript, lots of new features have been added this old but robust language.  Among them are lots of functional programming language related functions like map, filter, each etc. In this post, we will cover one function map and its interesting behavior. Before dive into the details, let first take an example, do you know the output of below function call? ['1', '7', '11'].map(parseInt) You may think that it's easy and the output would be [1, 7, 11] Can you try to ru...

   JAVASCRIPT,MAP,FUNCTIONAL PROGRAMMING     2019-06-14 08:34:46

  Something you may not know about Shell

Shell is also called command line interface, it is the interface between *nix users and computer. Shell is a program which provides service to access OS kernel services. This article is to introduce some not so well known but useful and interesting knowledge about shell. Wiki shell was born almost at the same time as Unix. The first UNIX shell was written by Ken Thompson in 1971 and its name is Thompson sh. It's older than Linux kernel. The default Shell in most *nix and MacOS is bash, bash was...

   Linux, Unix,Shell,Command     2012-11-24 07:19:47

  PHP to get access token for Facebook app

Since Facebook is now using OAuth 2.0 to authenticate apps to access user information. the SDK of Facebook has provided developers some useful functions to get authentication done. For example, in PHP SDK, there are getAccessToken(), getLoginUrl() etc. But unfortunately, for me I cannot use getAccessToken() method to get the user access token, it only returns me the app access token. Finally I gave up this approach to get access token for the time being. I may later retry this approach if I have...

   Faceook,PHP,Access token,signed request     2012-03-27 12:37:46

  PHP to integrate with Sign in with Google

Google has a huge user base and hence it provides an authentication service for third party service to integrate with them so that people can sign in with Google in their services. Google also adopts OAuth 2 to provide this kind of Open ID connect service. This post will introduce how to integrate with sign in with Google functionality in your PHP website.  Create a client app on Google The first step you should follow is to create a Google app, you can follow the post here to create the p...

   PHP,GOOGLE API,OPEN API,SIGN IN WITH GOOGLE     2019-03-03 02:00:09

  Understand GoLang WaitGroup internals and how it works

Background Before getting into the main content, let me give a brief introduction to WaitGroup and its related background knowledge. Here, the focus is on the basic usage of WaitGroup and the fundamental knowledge of system semaphores. For those who are familiar with these, you can skip this section directly. WaitGroup WaitGroup is one of the most common concurrency control techniques in Golang, and its function can be roughly compared to the join() in concurrency control of other languages' mul...

   GOLANG,WAITGROUP,SOURCE CODE     2023-04-26 08:02:01

  Python threads: communication and stopping

A very common doubt developers new to Python have is how to use its threads correctly. Specifically, a large amount of questions on StackOverflow show that people struggle most with two aspects: How to stop / kill a threadHow to safely pass data to a thread and back I already have a blog post touching on these issues right here, but I feel it’s too task-specific for sockets, and a more basic and general post would be appropriate. I assume the reader has a basic familiarity with Pytho...

   Python,Multithreading,Communication,Synchronize     2011-12-28 07:38:32

  Permutation implementation in Java

Permutation is a very basic and important mathematic concept we learned in school. It has very practical applications in real world. For example, in football. In simple, permutation describes all possible ways of doing something. For example, there are six permutations of the set {1,2,3}, namely: (1,2,3), (1,3,2), (2,1,3), (2,3,1), (3,1,2), and (3,2,1). In general, for n items, there are n! number of permutations to arrange these items. How can we implement this algorithm in programming programm...

   Permutation,Implementation,Java,Sample     2015-03-26 02:18:14

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