In this post, I want to show how I use NLTK for preprocessing and tokenization, but then apply machine learning techniques (e.g. building a linear SVM using stochastic gradient descent) using Scikit-Learn.
All of these samples perform essentially the same task: traverse an array of strings and print each value to stdout. Of course, the C++ example is actually using a vector rather than an array due to the evil nature of C/C++ arrays, but it comes to the same thing. Passing over the differences in syntax between these four languages, what really stands out are the different ways in which the task is performed. C++ and Java are both using iterators, while Ruby and Scala are making use of higher order functions. Ruby and C++ both use lowercase variables separated by underscores, while Java and Scala share the camelCase convention. This is a bit of a trivial example, but it does open the door to a much more interesting discussion: what are these idioms in Scala’s case? Scala is a very new language which has yet to see truly wide-spread adoption. More than that, Scala is fundamentally different from what has come before.
That should be it. You now be able to boot up you Lift app, launch the Flex app, click the “Subscribe to ‘notifications’” to start the Notifier Actor and subscribe to the Consumer to the notifications destination. You should then see id number and the time in the text input field get automatically updated every 0.5 seconds. You can the click the “Unsubscribe from ‘notifications’” to stop the Notifier actor and the Consumer to unsubscribe from the notifications destination. Pretty exciting. With these three technologies it’s really easy to automatically push data from the server to the client in real time. This is obviously a trivial example, but I think it should be relatively straight forward to scale this approach up for more sophisticated apps.
Once you start thinking about structuring your code to use Option in languages which have built-in support for it, you’ll find yourself dreaming about such patterns in other, less fortunate languages. It’s really sort of bizarre how much this little device can open your mind to new possibilities. Take my code, and give it a try in your project. Better yet, implement something on your own which solves the problem more elegantly! The stodgy old Java “best practices” could use a little fresh air. P.S. Yes, I know that the original implementation of this was actually the Maybe monad in Haskell. I picked Option instead mainly because a) I like the name better, and b) it’s Scala, so it’s far more approachable than Haskell.
For some reason, I suddenly felt like playing around with Scala for a couple of days, and having gotten over my perceived difficulty of the language vs Groovy, and after actually trying to write something in it - I really like it :) At first glance, advanced functional programming in Scala can look a little freaky to someone who’s only been writing Java for the last few years. But if you start slowly, it all slides into place. I started to get into it by reading this is a really good series of articles introducing the language What follows are two examples of Scala. The first, LoveGame is a demonstration of programming a simple algorithm in Scala along with a little comarpison with Java. The second is a little toying around i did with Scala to create a front end for JScience with the “Pimp my library” pattern.
Just fire up your REPL and see for yourself how the malleable syntactic structures of the language grow in front of your eyes, alongside your program. Whether this is through Lisp macros or Ruby meta-programming or Scala control structures, the secret sauce is in the ability to implement more and more powerful abstractions within the language. But what makes one language shine more compared to another is the ability to combine abstractions leading to more powerful syntactic structures. Recently people have been talking about the Maybe monad and its myriads of implementation possibilities in Ruby. Because of its dynamic nature and powerful meta-programming facilities, Ruby allows you to write this .. @phone = Location.find(:first, ...elided... ).andand.phone Here andand is an abstraction of the Maybe monad that you can seamlessly compose with core Ruby syntax structures, effectively growing the Ruby language.
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