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  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

  SOME LESSONS LEARNED

Note: Google was kind enough to invite me to give a short talk at their Zeitgeist conference earlier this week. It was a really interesting conference and I got a chance to meet a lot of people I admire. For my talk, I decided to use material from some of my blog posts over the years that I thought might appeal to a broader audience. Unfortunately, I was still recovering from a nastly cold/flu so I didn’t deliver the talk as well as I’d like.  Below is the text.Today, I wanted...

   Investor,Startup,Lesson,Experience,Investment     2011-10-12 11:47:02

  Webinar Best Practices For A Webinar Experience Your Audience Will Love

The web conferencing technology has been getting a lot of attention lately, and for good reason. With global lockdowns and social distancing norms in effect, video conferencing has emerged as an economical way of staying in touch with office colleagues, friends, and family members. However, if that’s all you are using this technology for, you may not fully understand what is web conferencing and its immense potential. For instance, lately, web conferencing technology is being used to deliv...

   WEB CONFERENCE,WEBINAR     2020-11-07 04:19:52

  Live in Beijing and Thinking about Starting a Tech Company? Read. This. Post. Now.

The Disrupt Beijing Hackathon starts in a little more than 24 hours, and we’ve been working hard over the last few days to make it even more of a no-brainer for local Beijing developers to attend.In addition to the chance to be the next GroupMeor win valuable prizes, we have decided to give all Hackathon attendees who complete a hack and present in the 24-hour period free tickets to the Disrupt conference Monday and Tuesday. That’s a $1,000-plus value for s...

   Startup,Beijing,TechCrunch,Disrupt,2011     2011-10-28 12:41:43

  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

  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

  HTML5 photo taking and uploading app implementation

Underthe support of HTML5 standard, Building Web App to take photos is now possible.I will elaborate on how to take photos using Web App, display them on the pageand upload them to the server. 1.     Videostream HTML5 TheMedia Capture API provides the programmable  access to video camera on phones, users canuse the getUserMedia() method to get the video stream provided by video camera.What we need to do is to add a HTML <video> tag and make the videostrea...

   HTML5,Photo taking,Media Capture API ,Implementation     2012-03-15 07:19:49

  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

  How to handle ES6 modules in NodeJS

In modern JavaScript, there are two types of modules: ES6 module and CommonJS module used by NodeJS. These two types of module are not compatible. Many people would wonder how to load ES6 modules in their NodeJS project. This post will show how this can be done. Difference The syntax of the module being loaded is different. CommonJS modules are loaded with require() and exported with module.exports. ES6 modules are loaded and exported using import and export respectively. Merchanismwise require(...

   NODEJS,COMMONJS,ES6     2020-08-28 22:01:33