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  errGroup in GoLang explained

Today, let's talk about the usage and applicable scenarios of errGroup, which is often used. Why is it useful? Generally, when we use goroutine, we cannot return a value. If you want to pass out the result of the goroutine execution, you usually have to use the channel. The errGroup package is suitable if you want to know when the goroutine you opened encounters an error during execution and stop working, and I need to know the error value. errGroup usage The package needs to be downloaded and i...

   GOLANG,ERRGROUP,WAITHROUP,CONCURRENCY     2023-05-27 23:58:20

  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

  Resolve git issue git@github.com: Permission denied (publickey)

Sometimes when clone a remote repository from github.com, you may see below error. D:\Project\Playground\GitBisect>git clone git@github.com:bradleyboy/bisectercise.git Cloning into 'bisectercise'... git@github.com: Permission denied (publickey). fatal: Could not read from remote repository. Please make sure you have the correct access rights and the repository exists. The issue occurs when there is no key on your machine which is associated with your github account. To fix the issue, please ...

   GIT,GITHUB,PERMISSION DENIED,PUBLIC KEY     2019-07-12 10:10:49

  Paint messages will come in as fast as you let them

There is a class of messages which are generated on demand rather than explicitly posted into a message queue. If you call Get­Message or Peek­Message and the queue is empty, then the window manager will look to see if one of these generated-on-demand messages is due, messages like WM_TIMER, WM_MOUSE­MOVE, and WM_PAINT. Neil wonders, "In that program that called Invalidate­Rect 100,000 times, how many paint messages were generated?" The Zen answer to this question is "Yes." A ...

   WM_PAINT,paint message,work,Mouse move     2011-12-21 09:37:14

  Output a file with HTTP range header in PHP

When downloading a large file, we may encounter some network issues which causes download termination and only part of the file is downloaded. When the network connection resumes next time, we may need to redownload the file again from the beginning. In order to save bandwidth, http provides a Range parameter in its header which can control the file transfer flow. With the range parameter in the header, we can resume the download from where we stop. Here is a piece of PHP code snippet which uses...

   PHP, range,http, file transfer     2013-01-09 05:55:05

  We need a programming language for the rest of us

Recently I took on the enormous task of learning Objective-C from the bottom up and I was struck by something I couldn’t shake: this is too hard. An experienced developer might scoff at me for saying that, but it’s true. I’ll be honest about my education, Calculus II was the most math I ever took, I have an advanced degree from Berkeley in Journalism. I am a proficient HTML/CSS developer and can glue enough javascript together to solve almost any problem that has presen...

   Code.Programming,Expectation,Easy-to-use     2011-07-22 02:20:09

  Understand JavaScript prototype

For an front end programming language like JavaScript, if we want to understand its OOP feature, we need to understand its objects, prototype chain, execution context, closure and this keyword in deep. If you have a good understanding on these concepts, you should be confident that you can handle this language well. The inheritance in JavaScript is not class inheritance like Java, but it adopts another mechanism-- prototype inheritance. The key to prototype inheritance is the prototype chain mec...

   JavaScript, prototype, __proto__     2013-02-02 02:34:09

  Using C for a specialized data store

Pixenomics stores and transports 1.2 million pixels from the server to the client. During development we played with various methods to store and process this. Our ultimate goal was to send the entire board in under 1 second. During the stages of prototyping we used a MySQL database without thinking too much about performance. With a mere 2,000 pixels we quickly realised this wasn’t even usable as a demo. Changing the storage engine to memory was much better but still obviously unu...

   C,Data store,Efficiency,Performance     2012-03-07 05:09:38

  The tic-tac-toe game with Python

In this tutorial, we will show how to build a tic-tac-toe game with Python. We will use functions,arrays,if statements,while statements, for loops and error handling etc. First, we need to create two functions, the first function will display the borad of the game: def print_board(): for i in range(0,3): for j in range(0,3): print map[2-i][j], if j != 2: print "|", print "" Here we used two for loops to loop through the map, this map is...

   Python,Tic-Tac-Toe     2013-07-30 02:49:09

  Method chaining and lazy evaluation in Ruby

Method chaining has been all the rage lately and every database wrapper or aything else that’s uses queries seems to be doing it. But, how does it work? To figure that out, we’ll write a library that can chain method calls to build up a MongoDB query in this article. Let’s get started! Oh, and don’t worry if you haven’t used MongoDB before, I’m just using it as an example to query on. If you’re using this guide to build a querying library...

   Ruby,Method chaining,Lazy evaluation,Implementation     2011-11-29 08:51:17

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