HOW-TO: Poor Man’s Quiz Scorer in Emacs Lisp

Sometimes it’s about small data.

Recently I’ve been studying a topic using a book, and at the end of each chapter there are quizzes of 20-25 questions. My method was to open a text buffer in Emacs, and vertically note down the question number, my answers, and after finishing this, go to the correct answer list, and mark correct answers with Y, and wrong ones with N:

Y 1- A,B,C
Y 2- C
N 3- D
N 4- C
Y 5- A
Y 6- B,C,D
Y 7- B

That was all fine, but I found myself counting the number of correct answers, and calculate my score in terms of percentage manually. I could of course quickly run the `M-x count-matches` (or `how-many`) to see how many correct / wrong answers I had, but doing this more than a few tests seemed to become tedious. Therefore, Emacs Lisp to the rescue!

With this simple Emacs Lisp function, assigned to F12 function key, I can now simply hit F12 and see my score percentage in Emacs:

“Your test score percentage: 71.42857142857143”

There are of course alternative methods to solve this straightforward problem, e.g. you can run some shell scripts on your Emacs (or VIM) buffer, or on a simple text file. But I like this solution being self-contained in Emacs, as well as the fact that it’ll continue to run as intended 30 years from now, in a newer Emacs version probably. This, and the fact that, my preferred tool for dealing with textual data gives me the flexibility to program it any way I want. It might have its drawbacks, it might be showing its age in its architecture, there are newer, shiny tools, there are specialized IDEs for various programming languages I use, but all of these notwithstanding, I still like to think it’s a beautiful thing that an editor released when I was born, that helped me with many tasks for decades, will still be with me for decades to come.

 

One year with “Haskell Programming from First Principles”

My relationship with the Haskell programming language, my efforts to learn it had its ups and downs throughout the years. According to my memory and the archives of my blog, my first attempts had been around 2005 – 2006, more than 12 years ago. Back then, apart from a few books written by university professors, and some Wiki-based books, I couldn’t find much high quality material for beginners. Therefore, my efforts didn’t last very long. A few years later, I heard the news about a new book, “Real World Haskell” being written. I was excited once again, I even made a few comments here and there as the book was being written. Unfortunately, life happened, and I couldn’t spend much time on that nice book, too. Fast forward to the end of 2015, and I was working at a company in Ghent, Belgium where there were some Haskell experts, trying out things in an industrial storage system development environment. The teams that I was part of had nothing to do with Haskell though, my daily job was almost always about Python, Bash, ActionScript, Java, and some Scala. Nevertheless, being in such an environment rekindled my curiosity, and I decided to look around to see if there was some new Haskell books targeted at people who didn’t use this language before. Luckily, I’ve heard about the book “Haskell Programming from First Principles“, and I decided to give it a try. Therefore I bought the book, and started to read and study it in the beginning of 2016. Since Haskell was not at all used in my daily job, I could study the book only in my spare time, therefore it took me about 1 year to finish the book, doing most of the exercises.

 

For the Love of Books: Turkey versus Belgium

The 80. edition of Antwerp Book Fair (Boekenbeurs) has finished recently. Shortly after that, another book fair, 35. Istanbul Book Fair took place. I was curious to compare the number of visitors, and especially the percentage of book fair visitors by taking the population of the city into account.

Istanbul is home to about 15 million people. Of these 15 million people, 558 thousand visited the fair in 9 days. On the other hand, the population of Antwerp is about 500 thousand people, and out of that, 170 thousand people visited the fair in 10 days on average in 2010 to 2012. In terms of percentage, the picture looks like the following:

In other words, 3.7% of Istanbul visited their book fair, whereas 34% of Antwerp population visited their book fair. If 34% of Istanbul’s population visited the book fair, that would make ~ 5.1 million people in 9 days.

This picture tells us something about literacy and interest in books, but of course we should always ask the question: how representative such a crude statistic is? Another interesting fact is that Istanbul makes up about 20% of Turkey’s population, whereas Antwerp makes up about 4.5% of Belgium’s population. (If we want to compare Turkey to a country with similar population and its most populated city: Germany is close to Turkey with its 80 million people, and its most populated city, Berlin, is home to 3.4 million people. In other words, Germany’s most populated city makes up only 4.25% of the Germany’s population.)

 

Faster, RegEx! Match! Match! (Which Regular Expression Utility is the Fastest?)

When it comes to dealing with text data, regular expressions are the bread and butter of data processing, as well as programming, most of the time. Hardly a day or two passes before you use grep or a similar tool. Until recently, I thought the field of regular expressions and related tools were very useful, boring, and didn’t present any innovations. It turns out that I was wrong!

There are two relatively new players in town: ICgrep and ripgrep.

ICGrep uses a new, parallel bitstream technology, developed Dr. Robert D. Cameron at Simon Fraser University. It claims to be super fast for many text search and processing tasks. ICGrep is available for download from http://www.icgrep.com/downloads.htm as a binary executable for OS X / MacOS. Its source code is also available if you want to build it for your operating system.

ripgrep is developed mainly by Andrew Gallant and other open source contributors, and its source code is available at https://github.com/BurntSushi/ripgrep. It is developed in Rust programming language, and claims to be very fast, Unicode-ready, as well as smart; ready to replace the Silver Searcher (ag), and “ack“.

Let’s see how they compare to the venerable regular expression utilities that we all know and love.

 

How to decrease the Maven build time of your Java projects

There are good resources on the web that shows how you can decrease the Maven build times of Java projects, but since I couldn’t find the following information in most of them, I wanted to note this down for future reference. One of the simplest things you can do to decrease the Maven build time is to add the following to your command line:

-Dmaven.javadoc.skip=true

But is it worth it? Let’s check. Take an example project such as Hadoop that is about 2 million lines of source code. Without skipping the generation of Javadoc,

 

Turkish Mode for Emacs is now available as a package via MELPA

Turkish Mode for Emacs, developed by Deniz Yüret, is now available as a package via MELPA. This is for people trying to type Turkish documents on a U.S. keyboard using Emacs. The program provides a `turkish-mode` in which the correct Turkish accents are added to the ASCII version of the last word typed each time the user hits space. If you are using a recent stable version of Emacs that lets you use the Emacs package manager, and you’ve added MELPA as a repository, installing it is as easy as running:

M-x package-install turkish

and then putting the following line in your init file:

(require 'turkish)

Once you have done that, in any Emacs session you can toggle the Turkish mode

M-x turkish-mode

The same program has been converted to many different languages and available on many platforms such as a Python package, a Java package, a Perl CPAN package, an Ubuntu PPA package, a web application,  a Chrome plug-in, a Firefox add-on, and a Safari add-on.

 

How to comment your code: an example from Hadoop

How to comment your source code? This topic comes up every once in a while, and sometimes it leads to heated discussions. The consensus is something like “comment why, and not how”. Useful as it seems, I think it is important to give examples from real-world scenarios. So, let’s look at such a case.

I’ve been working on the integration between Hadoop and HGST Active Archive S3 Object Storage product recently, and while dealing with the internals of the S3A File System that we are improving at the company, as well its interaction with YARN,  I’ve come across an interesting piece of code in the Hadoop code base. Before going into its details, look at it without any comments: