Zaemis

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OO in Language Design

If you were to create a new programming language, and you wanted to support object oriented programming with it, what would it look like? An object is a set of instance data and various functions that work with it. In Java, they're specified by first grouping the variables and functions together in a class, and then creating an instance from the class definition. In JavaScript, functions are dynamically attached to the instance data (or it's prototype). This is an intentional over-simplification but does highlight the fact that different programming languages approach working with objects differently. I've been thinking about objects and working with structured code in relation to Kiwi and it depresses me how much the object oriented school of thought that started with C++ and came to fruition in Java has influenced our industry. Of course there are the so-called five concepts of object oriented design , which says a design that meets the following criteria is considere...

Spaghetti Code Considered Harmful

To chefs and epicureans, spaghetti is a good thing-- it's inexpensive, easy to make, and very versatile. But spaghetti isn't so appetizing to a programmer. The phrase "spaghetti code" is an all-too-common pejorative we programmers use to describe horrible code, whether it's difficult to understand, poorly organized, or just plain long-winded. And there-in lays the problem. What really constitutes spaghetti code is subjective; I've yet to hear a concrete definition or standard metric that measures it. I've seen PHP code that amounts to nothing more than a giant switch construct... a hundred lines here to handle this condition over here, another hundred or so lines in the branch for that condition over there, maybe a dozen conditions... you get the idea. But such code isn't necessarily spaghetti. What's wrong with it is not that it's unreadable, I would argue, but rather there is a lack of encapsulation. There's a greater chance of inadver...

Resuming scp

I was transferring a file from one system to another at work with scp when the connection dropped. It was a substantially sized file and I didn't want to start the transfer over again, but unfortunately scp doesn't support resume. That's when I remembered rsync. With rsync I was able to continue the transfer where it left off, and afterward I had the idea to set the following alias in my .bashrc file. alias scp='rsync -vPe ssh' Now when I transfer files with scp, I'm really using rsync and I don't have to worry about flaky network drops.

Creepy JavaScript Tracking

I recently began allergy shots so my new Monday morning routine includes me sitting in a doctor's office for 30 minutes (I must wait after receiving the shots and be checked by a nurse to make sure there was no reaction). With nothing else better to do while I waited last week, I started playing around with some JavaScript. This is what I came up with: <html> <head> <title>Test</title> <script type="text/javascript"> window.onload = function () { var mX = 0, mY = 0, sX = 0, sY = 0, queue = [], interval = 200, recIntv = null, playIntv = null, b = document.body, de = document.documentElement, cursor = document.getElementById("cursor"), record = document.getElementById("record"), play = document.getElementById("play"); window.onmousemove = function (e) { e = e || window.event; if (e.pageX || e.pageY) { ...

Geolocation Search

Services that allow users to identify nearby points of interest continue to grow in popularity. I'm sure we're all familiar with social websites that let you search for the profiles of people near a postal code, or mobile applications that use geolocation to identify Thai restaurants within walking distance. It's surprisingly simple to implement such functionality, and in this post I will discuss how to do so. The first step is to obtain the latitude and longitude coordinates of any locations you want to make searchable. In the restaurant scenario, you'd want the latitude and longitude of each eatery. In the social website scenario, you'd want to obtain a list of postal codes with their centroid latitude and longitude. In general, postal code-based geolocation is a bad idea; their boundaries rarely form simple polygons, the area they cover vary in size, and are subject to change based on the whims of the postal service. But many times we find ourselves stuck on ...

Ubuntu Packages Please Get Your Act Together

I didn't intend to write another blog entry so close to the conclusion of my Week with Go series, but my experiences earlier today definitely warranted a rant. Installing the SpiderMonkey JavaScript engine for use as a stand-alone interpreter on Ubuntu 10.04 LTS doesn't sound like outlandish goal. After all, CouchDB ships by default as of 9.10 and it requires a JavaScript run-time. Technologies like node.js and v8 are pretty hot right now so there might even be a few alternatives to choose from, right? WRONG! sudo apt-get install spidermonkey-bin E: Couldn't find package spidermonkey-bin There used to be such a package but apparently SpiderMonkey is "unsupported" now and was removed from the Universe repository. Sorry Ubuntu. I'm not feeling the love for Rhino. It doesn't do JIT and runs slower than a one-legged sloth. Besides, I don't feel like installing ca-certificates-java , default-jre-headless , icedtea-6-jre-cacao , java-common , libavahi-...

A Week with Go, Day 5

Concurrent programming in Go makes use of coroutines, which are quaintly called "goroutines", and channels. Coroutines are functions executed asynchronously from the rest of your program, and channels are synchronous pipes through which the routines communicate. I had written a multi-threaded Kember Identity program in C a while back, and decided to rewrite it in Go to gain some exposure working with these features. The Effective Go primer gives a hint of what goes on under the hood with coroutines in Go. A goroutine has a simple model: it is a function executing in parallel with other goroutines in the same address space. It is lightweight, costing little more than the allocation of stack space. And the stacks start small, so they are cheap, and grow by allocating (and freeing) heap storage as required. Goroutines are multiplexed onto multiple OS threads so if one should block, such as while waiting for I/O, others continue to run. Their design hides many of the compl...

A Week with Go, Day 4

Day 4 was spent learning about Go's take on object oriented programming, which I found to be a refreshing change from the likes of Java and C#. It's not type-focused; instead of relying on an object's type to know whether or not it offer certain functionality, the object will generally implement an interface. This mindset is not dissimilar to good JavaScript programming where feature detection is preferred over browser sniffing. The code doesn't care what something is (browser/object), just what it can do (functionality/interface). The word "object" is probably a bit misleading since Go doesn't really have them in the traditional sense. There's no need to write a class definition as in Java, nor to instantiate an object literal like JavaScript. The programmer specifies a set of functions and Go's compiler deduces the relationships. type Rectangle struct { width float height float } func (r *Rectangle) Area() float { return r.widt...

A Week with Go, Day 3

The first two days of tinkering and scouring helped me form an opinion of Go based on its syntax. To form a more-informed opinion I would have to write some more code and see how much resistance I experienced along the way. What features were missing? How was typing applied? I wrote a rudimentary version of Deal or No Deal , and slowly some of those meaningless sections in the language spec started taking on more meaning. I decided to store the case amounts as an integer array (nobody likes the 0.01 anyway!) and came across my first bit of frustration and misunderstanding when it came time to shuffle the amounts. cases = []int{100, 200, 300, 400, 500, 750, 1000, 5000, 10000, 50000} shuffle(cases) func shuffle(arr []int) { rand.Seed(time.Nanoseconds()) for i := len(arr) - 1; i > 0; i-- { j := rand.Intn(i) arr[i], arr[j] = arr[j], arr[i] } } The language spec says arrays are value types and slices are reference types. shu...

A Week with Go, Day 2

After dabbling a little bit on day 1, I dedicated some time on day 2 to skim through Go's language spec and standard libraries . A lot of it didn't have much relevance to me yet because I hadn't begun to play with those parts of the language. What caught my eye though was that Go supports the \v escape (obviously no one at Google has read Stop the Vertical Tab Madness ). Welcome to 1963, folks. In addition to tweaking how loops are written, Go has augmented the traditional syntax of if and switch statements too. I don't see the enhancement providing as much benefit as I do with for . It's almost as if someone decided to let people move the placement of if up a statement earlier just to be different, and it certainly doesn't read well. x := recover() if x != nil { ... } vs if x := recover(); x != nil { ... } The list of available packages is rather impressive considering Go has been available for a year. Some packages are pretty standard, like math and...