Today's Question:  What does your personal desk look like?        GIVE A SHOUT

SEARCH KEYWORD -- Hash code

  A Perl Regular Expression That Matches Prime Numbers

perl -lne '(1x$_) =~ /^1?$|^(11+?)\1+$/ || print "$_ is prime"' Can you figure out how it works? I give an explanation below, but try to figure it out yourself. Here is what happens when you run it: $ perl -lne '(1x$_) =~ /^1?$|^(11+?)\1+$/ || print "$_ is prime"' 1 2 2 is prime 3 3 is prime 4 5 5 is prime 6 7 7 is prime 8 9 10 11 11 is prime Here is how it works. First, the number is converted in its unary representation by (1x$_). For example, the number 5 gets converted into 1x5, which is ...

   Perl,Regex,Regular expression,Prime number,One line     2011-12-26 08:42:00

  Why is single threaded Redis so fast

Redis is a high-performance, in-memory key-value database. According to official test reports, it can support around 100,000 QPS (queries per second) on a single machine. However, Redis uses a single-threaded architecture in its design. Why does Redis still have such high performance with a single-threaded design? Wouldn't it be better to use multiple threads for concurrent request processing? In this article, let's explore why Redis has a single-threaded architecture and still maintains its spe...

   REDIS,SINGLE-THREADED,MULTI-THREADING     2023-02-28 05:16:22

  Rediscovering the RSync Algorithm

A:Ok, you’re synchronizing this over the web; and what do you use for the synchronization? B: Oh, we implemented the rsync algorithm. A: uhu. And what do you do with really big files? B: The same. A: And you also synchronise folders? B: Yes. A: And how do you do that? B: we iterate over the folder, using the algorithm on every file, recursing over subfolders. A: Can you try 2 things for me? First, a very large file; and second, a large codebase, and see if it holds. Introduction First ...

   ReSync algorithm,Discovery     2012-02-14 10:47:24

  C/C++ Pointer Declaration Syntax – It makes sense!

I never really liked the way pointers are declared in C/C++: int *a, *b, *c; // a, b and c are pointers to int The reason is that I am used to reading variable declarations as MyType myVar1, myVar2, myVar3; and I always read “int*” as the type “integer pointer”. I therefore wanted the following int* a, b, c; // a is a pointer to int, b and c are ints to mean that a, b and c all were of type int*, i.e. pointers to int. and I therefore found it slightly a...

   C,Pointer,Declaration,Attempt     2012-02-22 05:43:58

  Becoming a Better Developer, Part 2: Know Your Core Competencies

If you're trying to grow your startup you've come to the right place. Get my 170-page ebook on how to grow a startup and join thousands of self-funded entrepreneurs by subscribing to my newsletter at right. For years business consultants have instructed businesses to “know your core competencies.” What this means is “know what you do well and stick to it.” For example: Harley Davidson makes great motorcycles. But they’re probably not so good at making per...

   Developer,Tips     2011-06-29 08:40:10

  Understand diff in Unix

diff is an important tool program in Unix. It is used to compare differences of two files, it is the foundation for code version control. If you type : $ diff <file_before_change> <file_after_change> diff will tell you what's the difference between these two files. The result may not be so easy to understand, so now I will show you how to understand diff. 1. 3 formats of diff diff has 3 formats due to historic reasons. normal diff context diff unified diff 2. Demo files For easy d...

   diff,Unix,version control,git     2012-09-03 10:49:36

   Move.Me Writing Your Own WebSocket Server

The WebSocket protocol has applications beyond plain vanilla web development.  I will explain how the protocol works, how to implement your own server and share some insights I had along the way. Before we get down and dirty, I will explain what I’ve been doing with it. At this point I expect many of you are saying “I’m not working on a web game this doesn’t seem relevant to me.” Well, neither am I. I embed a WebSocket server into my game engine and wit...

   Socket,NetWorking,WebSocket,Server development     2012-01-28 07:06:43

  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

  About go get and go install in Go 1.16

Go version 1.16 beta1 has been released on 18 Dec 2020, major features of Go 1.16 have been finalized with this beta release. Many people are discussing about the support of Apple M1, however, this post will not cover this topic. Instead the focus will be on go get and go install changes. There are lots of changes related to modules in Go 1.16, the details can be found in the release note. Below are some of the key highlights. GO111MODULE is on by default, if wanna keep old behavior, needs...

   GOLANG,GO 1.16,GO INSTALL     2020-12-26 00:26:58

  A Javascript When Function

function when(conditionFunc, execFunc, interval){ if (conditionFunc()){ execFunc(); }else{ setTimeout(function(){ when(conditionFunc, execFunc, interval);}, interval); } } You have some code which should only execute when a condition is true. E.g. You have code which relies on a javascript library but can't be sure the library has loaded yet and don't want the code to execute until it has. This is common if you have a bookmarklet which injects more than one <...

   JavaScript,When,Implementation,When function     2012-02-24 05:08:34

RECENT