Serabe Reloaded » Programming

Adding organization repos to Travis-CI: Part I

Serabe — Sun, 09 Oct 2011 21:30:53 +0000

It was a nice Friday, Porras and I were at the BeBanjOffice and we were working on adding organization support to Travis-CI.

First, we needed to find where the user repos were being fetch. Said and done, we found that travis is using the ServiceHookController to ask the server for repos (and to update them too, but don’t hurry, we’ll get there in part II). The controller was using the github_repositories method in the User model. Finally, we arrived to Travis::GithubApi, where all our questions found answers.

repositories_for_user just relied on Octokit#repositories for getting the repos, so we added all the code after the plus sign. You might think that this code lacks the proper security, is wrong and that it shouldn’t be there (and damn it, you’re right!) but there is no easy way to retrieve only the repos where the user has admin privileges (we wasted hours on this and a quick message to Github confirmed it). Basically, it asks for all organizations for the given user (beware! You need to make your membership public, otherwise it won’t work) and then flat_map them to the repos in the given organization (whether the user can administrate them or not).

Later, the each block was added so we could know whether the repo belongs to the user or to an organization.

Stop! Hammertime!

We needed a way to let the user know that a repo actually belongs to an organization, so we added that info to the template (that {{#if content.organization_name}} is ours ) and added some style so it could look this awesome:

We had some tough time trying to get it vertically centered, but after realizing that Github has its tags the same way as we do, we stop trying to fix it. And they still look awesome.

More coming in part II.

Transforming CSS selector to an XPath query

Serabe — Fri, 09 Sep 2011 18:42:41 +0000

So. Easy.

PLAIN TEXT

RUBY:

require 'nokogiri'; Nokogiri::CSS.xpath_for(css_selector)

The Essential Guide to HTML5: a review

Serabe — Sun, 02 Jan 2011 21:57:47 +0000

After reading this book I have some encountered feelings about it: on the one hand the content is correct, everything I tested worked fine, etc but on the other hand I really find annoying the form it is presented.

When I started reading, I expected to find more about CSS3 (a topic almost not covered in the book) and less Javascript, but since this is only an expectation, I'll try my best so it doesn't affect this review.

Since I wrote before, the content is correct. Covers a huge part of the new apis, the examples usedare not too complex yet interesting and it is not hard to follow. Without any doubt, the form code snippets are displayed. The code is displayed in a two-column table (one for code, one for comments) and each line (each line!) is commented. Seriously, I've seen the line commented!

And even if the content is good, the table issue makes it really hard to read if you are a medium-experienced programmer. These are my encountered feelings: good content, not that good layout.

Creating a blur effect with rinzelight.

Serabe — Sun, 31 Oct 2010 20:55:56 +0000

After releasing rinzelight 0.0.3, I wondered how hard addinga blur effect would be. So I started implementing it.

We are going to do two 1D blur. In first place, open a repl and start emacs (or vim). Use rinzelight.image for reading northern-lights.jpg

First, let's start creating a blur-kernel function with two parameters, width and sigma. Rinzelight lacks of a kernel-rank constant, so let's add it. Open src/rinzelight/constants and add the following line to the end:

We get a horizontal kernel, which we will apply twice, one horizontally and one vertically. For getting a vertical kernel, we write one final function called transpose-horizontal-kernel:

And now, we are ready to write the blur effect:

And this is the result of a (blur (read-image "samples/northern-lights.jpg") 5 1.5 repeat-op rendering-quality):

(blur img 5 1.5 repeat-op rendering-quality)

And that's it!

Introducing rinzelight 0.0.2

Serabe — Sun, 17 Oct 2010 11:49:56 +0000

I started writing rinzelight long time ago. Exactly, I started on February. Sadly, since I wasn't getting a few points about Clojure, I stopped working on it twenty days after for half a year.

But do not let me digress. Rinzelight is finally released! Actually, rinzelight 0.0.2 is released! But let me introduce you to rinzelight.

Opening an image.

Just use rinzelight.image namespace. Then, just provide read-image of a filepath or an InputStream. Just like this:


301 Moved Permanently

301 Moved Permanently
nginx/1.0.4

A hash?

Yes. Four fields: image, format, width and height.

It's an image. Let me see it!

Command your repl to display-image.

What about saving it?

The correct spell is write-image. Just give it an image and an uri.

I want to change an image's nature.

If you want to, you can. Just look for namespaces under rinzelight.effects. Lookup tables and affine transforms are already available. There are even map-image and map-pixel-location functions. If you want to use map-pixel-location, take a look at rinzelight.effects.helper-functions for a helping hand.

What about a few examples?

I hide them under examples. They are a bit obfuscated using criterium for benchmarking, but they are not hard to understand. For running them, use lein run. They'll take a bit, since I use them as benchmarks.

The One where I spent a morning because -0.5 turned to be parsed as 1/2

Serabe — Sun, 05 Sep 2010 19:54:52 +0000

This summer, I have been doing some amazing stuff for GeoGebra. First of all, I would like to thank two people: Miguel, my mentor, who guided me through all that really advanced mathematical stuff; and Heinz Kredel, JAS creator and developer, who answered all my questions and implemented my suggestions as quickly as I could write them.

This story is about a problem we found in JAS. It was really subtle, so I may need a brief introduction to the project I worked on: LocusEqu. That project retrieves the equation of "any" geometrical locus. If you don't know what a locus is, Wolfram Math World defines it as "the set of all points (usually forming a curve or surface) satisfying some condition" . LocusEqu generates a few EquationExpression, and then, by using a EquationTranslator, it generates a GenPolynomial object.

For translating doubles, it calls the BigRational constructor whose only argument is a String. This is the code:

Can you spot the bug? Look at the 21st line. If s is "-0.5", then n is new BigInteger("-0"), and that's what makes "-0.5" be parsed as 1/2.

Status update for GeoGebra.

Serabe — Mon, 12 Jul 2010 20:41:04 +0000

My contributions for the first part of the first part of GSoC 2010 can be divided in two: general improvements and coding.

General improvements

I made a few general improvements on GeoGebra:

Refactored build.dir in ant build file. Previously, build.dir wasn't in the root directory.
A few ant tasks were added, such compile-grammar, compile-oe (outside Eclipse), run-easyb and run-easyb-outside-eclipse.
SVN properties were set in order to work outside Eclipse. This way, .class files will be kept out of the repo without the intervention of any Eclipse plugin.
Easyb, a BDD groovy-based framework, has been included in order to test GeoGebra. It is not RSpec, but I guess it'll do.

Coding

First, I started creating a few EquationPoint classes, currently there are six EquationPoint children classes:

EquationFreePoint represents an independent point.
EquationSymbolicPoint represents a dependent point, EquationSpecialSymbolicPoint standing only for the locus point.
EquationNormalPoint and EquationPointVectorPoint are only auxiliar elements.

Then, a few EquationElement classes were added, these stand for the different constructions:

EquationElement is an abstract class containing a few basic methods:

forPoint: Given an EquationPoint, returns a String with the equation that means that the point is in the construction.
isAlgebraic: returns true if the construction is algebraic, and false otherwise.

Both EquationGenericCircle and EquationGenericLine are abstractions of specific line and circle contructions, all of them algebraic. EquationGenericSegment is to segment what EquationGenericLine is to lines. Obviously, EquationGenericSegment is not algebraic.

All of these classes are used together by EquationScope.

A pause for a screenshot.

Click for enlarge.

A glimpse into the future.

What to do next?:

Maybe Equation should be a proper class, not just a String.
More equations.
Working out the locus equation.
Not using an algorithm twice.

Writing your own JRuby extension. Part II: Creating your first class.

Serabe — Thu, 11 Mar 2010 23:06:04 +0000

What's the point of coding a JRuby extension if you don't create classes? Well, I cannot think of any case, but if you find one, please, let me know.

Do you remember Java's classes hierarchy? If so, you'll realize that Java objects inherit from java.lang.Object by default but that is not actually what we need. But how can we tell JRuby that our object inherits from Object, the king of Ruby world? The answer is so simple: just extend RubyObject! (There is a RubyBasicObject too) Taken from Nokogiri::XML::Node:

Of course, you can extend any other class, as long as it is a "Ruby object". For example, Nokogiri::XML::Document extends from Nokogiri::XML::Node, and we do not need to do anything special to reflect it, just extend XmlNode like XmlDocument does:

After talking a bit about hierarchy, let's talk about Java constructors. At least two parameters are needed: a org.jruby.Ruby object and a org.jruby.RubyClass object. Being the importance of the former quite obvious, the reason for the latter may not be so clear. Let me show you some real world code: Nokogiri::XML::Node's dup method. Take a look at the following test:

Both new and dup methods in subclass rely on Nokogiri::XML::Node's. In here, you can see the this snippet of code:

The rb_obj_class method returns the class of an object, in this case, self. This way, the new node will be an instance of the same class as the original node. That's the reason a RubyClass is needed in the constructor, in order to know which is the actual class being instantiated.

By the way, do not forget to call super with the Ruby and RubyClass objects.

Next step: creating methods.

photo credit: quinn.anya

Writing your own JRuby extension. First problem.

Serabe — Sun, 10 Jan 2010 23:09:22 +0000

Maybe, when requiring your just created extension, you get a LoadError. If it is the first time you require it, it is quite likely that you have not followed JRuby requiring conventions. If you want to know how require works, you can find the best documentation ever about it in the comment before org.jruby.runtime.load.LoadService class.

photo credit: cesarastudillo

Writing your own JRuby extension. Part I: BasicLibraryService.

Serabe — Fri, 08 Jan 2010 00:22:44 +0000

Note: not code in this post, but you can see the code in Github. Follow the links!

Writing a JRuby extension is very easy, but there are almost not post out there about it. As far as I know, there is only one, Ola's. It is a really good tutorial indeed, but it lacks some details that might be not-that-easy to solve. Please, take some time to read it and, if some details are different, do follow Ola's way.

Everything's ready now, so let's start talking about BasicLibraryService. If you take a look at Nokogiri4J sourcecode, in ext/java/nokogiri folder, you will see a NokogiriService.java file. NokogiriService implements BasicLibraryService. This interface consists only of the method basicLoad which receives a Ruby object.

We will use this method to define classes and methods in the Ruby world. For defining a module, defineModule method is used with the name of the module. After that, modules and classes under that module can be defined easily by using the methods defineModuleUnder, which takes the name as parameter, and defineClassUnder, which takes the name and few parameters more. Let's dive into it.

defineClassUnder needs three arguments. The first one is the class' name. The second, is the parent class. If you have defined it previously, just passed it, otherwise use RubyObject by calling the method getObject on the Ruby instance. The third parameter is an ObjectAllocator. ObjectAllocators returns intances of the classes in Java world. When instantiating Nokogiri::XML::Comment in Ruby world, JRuby will ask the ObjectAllocator for an instance of the Java class. It passes a Ruby object and the RubyClass being instantiated to the allocate method in the ObjectAllocator (more on RubyClass in following posts).

Finally, we will need to define some methods. Easiest way is by using the defineAnnotatedMethods. It takes a Java class as parameter. For knowing what this method does, you need to know a bit more about @JRubyMethod annotation (more on it in following post, have you realized the "Part I" in the title?). As you define methods, you may need to undefine some in a subclass. So easy! Use the undefineMethod method, which takes the name of the method as parameter (surprisingly, it undefines a method by redefining it!).

Next time, Implementing your first class.