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  How to write your own DSL in Ruby

DSL(Domain Specific Language) is a language defined to fulfill some domain specific requirements to ease people's work. It can be used to define attributes and actions of a domain easily and cleanly. And it is often created based on some common observations or micro patterns of some domain. In Ruby world, there are quite a few places people can find DSL. For example, Ruby itself, Chef recipes. To create a class in Ruby, the traditional OOP way would look like. class User @name = nil @email =...

   RUBY,DSL,TUTORIAL     2017-03-04 09:40:34

  An Object is not a Hash

Following my article A String is not an Error, I want to bring attention to an issue that similarly applies to JavaScript in general, but has special relevance in the Node.JS environment. The problem boils down to the usage of {} as a data-structure where the keys are supplied by untrusted user input, and the mechanisms that are normally used to assert whether a key exists. Consider the example of a simple blog created with Express. We decide to store blog posts in memory in a {}, indexed ...

   Object,Hash,Node.js,JavaScript     2012-01-19 10:16:10

  An alternative way to parse URL in JavaScript

Normally when we need to process URL in JavaScript, we may use the location object. Then we can use location.hostname,location.href,location.port etc to get the information we need. In this post, we will parse an URL with an alternative way. We can use an URL to create a DOM object by calling document.createElement("a"). The complete code is: function parseURL(url) { var a = document.createElement('a'); a.href = url; return { source: url, protocol: a.protocol.replace(':',''), host: a.ho...

   URL,location,parse     2014-03-03 07:05:11

  Mutli-inheritance bug between python 2.7 and 3.7

When we have run a py3.7 code under py2.x or a py2.x code under 3.x ,if a class do mutli-inheritance from 2 parent and the 2 parents also got inheritance from same parent, the different way to handle inheritance chain between python 2 and 3 will cause some running time bug: Assume we got this sample program inheritTest.py : # Purpose: Test mutli-inheritance different between python2 and 3 # Author: Yuancheng Liu # Created: 2019/05/16 class A: def getVal(self): print("cal...

   PYTHON,PYTHON 3,INHERITANCE     2019-05-16 08:33:52

  C++, Ruby and CoffeeScript complexity comparison

There are many programming languages around the world, they all designed to help programmer solve some problems, finish some tasks. These languages are often divided into different types, there are structural, object-oriented, functional, scripting languages etc. Some are easy to pick up such as Java, while some are thought to be difficult to learn such as C++. So how do we understand complexities of different programming languages?Many people agree that C++ is very complex languages, it has poi...

   Complexity, languages, C++,Ruby,CoffeeScript     2012-06-12 04:46:01

  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

  ECMAScript 5 Objects and Properties

ECMAScript 5 is on its way. Rising from the ashes of ECMAScript 4, which got scaled way back and became ECMAScript 3.1, which was then re-named ECMAScript 5 (more details)- comes a new layer of functionality built on top of our lovable ECMAScript 3. Update: I've posted more details on ECMAScript 5 Strict Mode, JSON, and More. There are a few new APIs included in the specification but the most interesting functionality comes into play in the Object/Property code. This new code gives you th...

   ECMAScript,Object,Property     2012-01-29 04:38:50

  How to undo git changes?

When using git for version control, there is frequent need on undoing commits due to some unexpected changes. This post will introduce how to undo changes with git command in different cases. Undo commit A common undo case is that some commit needs to be reverted as the commit contains error. In this case, the code is already committed. The command to revert the commit is git revert HEAD This command will add new a commit to the existing head to undo the previous commit. It will not change the p...

   GIT,GIT RESET,GIT REVERT,GIT CHECKOUT     2019-12-28 02:21:47

  Apple patent shows they are developing "Killer" 3D Camera

This is not the first time that Apple patent shows they have interest on 3D camera technology. In November last year, one Apple patent shows that Apple is developing advanced three-dimensional object recognition and verification technology. According to PatentlyApple report (March 30,2012) one patent released this week shows that Apple is developing a 3D camera technology for the future iOS devices. This 3D camera is described as an advanced component with advanced micro-lens, depth, chrom...

   3D Camera,Apple,Patent     2012-04-03 07:46:35

  Prototypes and Inheritance in JavaScript

Forget everything you know about object-oriented programming. Instead, I want you to think about race cars. Yes – race cars. Recently I was watching the 24 Hours of Le Mans –a popular racing event in France. The fastest cars in the race are the Le Mans Prototypes. Although these cars are built by car manufacturers like Audi and Peugeot, they are not cars you’ll see on the streets and highways of your home town. They are built exclusively for high-speed endurance ra...

   JavaScript,Prototype,Inheritance     2012-02-27 04:55:22

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