ACCU World of Code

Further Programming for the ZX Spectrum by Ian Stewart, Robin Jones Foundation by Isaac Asimov Crime and Punishment by Fyodor Dostoyevsky Structure and Interpretation of Computer Programs by Harold Abelson, Gerald Jay Sussman, Julie Sussman S…

I have used Linux at home for quite a few years, and a couple of years ago I changed my work machine from Windows to Ubuntu Linux. It’s made life at work better for me. Better for me This move has made me much more productive, saving valuable time and …

I installed LibreOffice into Lubuntu, but the spell checking didn’t work. It turns out I need to install a dictionary for my locale: sudo apt-get install myspell-en-gb I needed to restart LibreOffice, and then I got spell checking as I typed.

Yes. If your JSON contains integer numbers that represent Unix time (seconds since the “epoch”), and you parse your JSON to JavaScript, the range of integers that can accurately be represented is -9007199254740992 to 9007199254740992 (ref: EcmaScript s…

Code analysis tools can require a lot of configuration to be useful. Whilst some (e.g. Vera++ or cpplint) need very little configuration to make use of effectively, others such as PC-lint (and even, to a lesser extent, CppCheck) may need to be fed pret…

Code analysis tools can require a lot of configuration to be useful. Whilst some (e.g. Vera++ or cpplint) need very little configuration to make use of effectively, others such as PC-lint (and even, to a lesser extent, CppCheck) may need to be fed pret…

To embed a binary file (e.g. a png image) into Java source code: $ hexdump -v -e ‘/1 “%3i, “‘ myfile.png -119, 80, 78, 71, 13, 10, 26, 10, 0, 0, 0, 13, 73, 72, 68, 82, … Copy and paste the output into Java code like this: private s…

Caffeine wasn’t working for me. I got an error like this: dbus.exceptions.DBusException: org.freedesktop.DBus.Error.ServiceUnknown: The name org.freedesktop.ScreenSaver was not provided by any .service files Bug 1280449 contained the solution for me. …

Series: Setup, Menu, Drawing, non-Android, Working, Saving state. Android apps like Rabbit Escape need to save their state when asked, and restore themselves later. This happens when you rotate the screen, and could happen at various other times. Here’…

Series: Setup, Menu, Drawing, non-Android, Working, Saving state. Up until now, you weren’t sure to believe my promises that Rabbit Escape really was going to be an Android game, since I hadn’t actually got it running on Android. Well, the wait is over…

As it stands, lxpanel’s taskbar plugin (part of the LXDE desktop you get with Lubuntu) does not show urgent (flashing) windows if they are on a different virtual desktop from the one you are looking at. This seems wrong to me (I logged Bug 682), and th…

I am trying to fix a bug in lxpanel’s taskbar plugin, and needed to launch an urgent window. Here’s how I did it in a little python. #!/usr/bin/python # urgent.py — launch an urgent window (Copyright messages are at the bottom) # To use: # sudo apt-…

Series: Setup, Menu, Drawing, non-Android, Working, Saving state We’re planning to write an Android game. So why would we deliberately avoid Android while we’re writing it? To make sure we’re not overly-dependent on the Android ways of doing things, an…

Series: Setup, Menu, Drawing, non-Android, Working, Saving state I will be talking about how to write Android programs that share code with non-Android programs. The program I will be writing is a simple game. This time we’re writing a game loop and dr…

I’ve been trying to chase down a mysterious problem with emails going missing. The problem with things being missing is that you can’t see them, so it has been difficult to track down exactly what’s going on, but it became clear that we were receiving …

I have spent several months with no spam filtering in my postfix+dovecote+spamassassin+fetchmail+procmail setup, and no idea why. I had spamassassin enabled and working when I piped emails into it manually, and I had lines like this in my postfix maste…

Series: Setup, Menu, Drawing, non-Android, Working, Saving state I will be talking about how to write Android programs that share code with non-Android programs. The program I will be writing is a simple game. This time we’re making a simple menu struc…

[Screenshots of Minecraft on the Raspberry Pi can’t be made with VNC or screenshot tool like scrot, but they can be made with the excellent raspi2png.] We did some Python programming in Minecraft on the Raspberry Pi for our summer projects. Child 2 m…

Series: Setup, Menu, Drawing, non-Android, Working, Saving state I will be talking about how to write Android programs that share code with non-Android programs. The program I will be writing is a simple game. First, how to set up Android Studio:

In Emacs, company-mode (short for “complete anything”) is a framework for performing completion in buffers. It’s an alternative to the popular auto-complete-mode. company-mode supports extension via backends which provide the framework with lists of possible completions in various contexts. So, for example, there’s a backend that provides completion support for …

In Emacs, company-mode (short for “complete anything”) is a framework for performing completion in buffers. It’s an alternative to the popular auto-complete-mode. company-mode supports extension via backends which provide the framework with lists of possible completions in various contexts. So, for example, there’s a backend that provides completion support for …

Most programming languages have some wrinkles around unicode and strings*. In my ficticious language Pepper, there are no wrinkles of any kind, and everything is perfect. *E.g. JavaScript, Java, Haskell, Ruby, Python. There are several key concepts. …

Is enforcing truthfulness the opposite of beauty? Can 2 + 2 = 5? Improvements, corrections, further contributions are welcome. $ cat five.cpp #include <iostream> int operator+( int x, int y ) { return 5; } int main() { std::cout << 2 + …

We’re thinking about switching to Git for my work, and I want to be confident we can still support good code reviews if we make the switch. I am a big fan of in-person reviews, and for that, git difftool is enough but sometimes you need to do it asynch…

On my recently-upgraded to 14.04 Lubuntu machine, desktop sharing didn’t work. Here’s how I made it work: Once (to allow some Windows clients to connect without encryption): gsettings set org.gnome.Vino require-encryption false Then every time I want t…

A recent discussion on ACCU-general gave people an opportunity to share the warning flags they like to use with g++. I thought I’d write down the consensus as I understood it, mainly for my own reference: -Wredundant-decls -Wcast-align -Wmissing-declar…

At work we are considering whether we can use Git for our source control. I am a big fan of Git, so I’d like to see this happen. We only need to work against a central repository most of the time, so I’m looking at what servers might work for us. Updat…

I run an ejabberd server on an Ubuntu 12.10 box and this week I started getting notified by my IM client that the server’s certificate had expired. Here’s how I managed to generate a new certificate. WARNING: this process backs up, deletes and then res…

Sent via WriteToThem.com. More Info Dear Mr Hammond, I am writing to express my concern about the Data Retention and Investigatory Powers Bill (DRIP). I feel that forcing companies to store data on their customers is an unacceptable breach of the right…

Node.js is a way of writing your web applications wholly in JavaScript, which sounds like a terrible idea. However, it is also an asynchronous programming environment that has been proven to scale really well, and it’s a collection of libraries many of…

Ever wondered how a mocking framework like JMock or GoogleMock works? We’ll look at how to write a very basic example, and find out that Java is more flexible than you may have thought. Slides: A mini mocking framework.

Kathy Sierra on ‘Motivation Matters’ at Business of Software Europe. Last week our founder Anna attended the Business of Software Europe conference in Cambridge, and it was quite something indeed. Although the Business of Software Conference has been …

Kathy Sierra on ‘Motivation Matters’ at Business of Software Europe. Last week our founder Anna attended the Business of Software Europe conference in Cambridge, and it was quite something indeed. Although the Business of Software Conference has been …

C++ template meta-programming sounds harder than it is. So long as you can fight through some horrific syntax and understand recursive functions, you can write any algorithm you like and have it run at compile time in your C++ programs. Slides: Simpl…

A quine is a program that prints out its own source code. I will describe five examples: Slides: Five Quines Arguably the greatest program ever written: Qlobe. More info on quines: http://www.madore.org/~david/computers/quine.html https://en.wikiped…

Series: What is REST?, A Basic REST API, Paging, Search, Security, Token, OpenID. We are implementing a REST API. Today, using OpenID to do our authentication, instead of doing it ourselves: Slides: OpenID security in a REST API. Code: poemtube on gi…

You probably already know how to use Python’s super() to call base-class implementations of methods. But do you really know what it’s doing? The details of super() are elegant, interesting, and powerful, and while super() is probably more complex than you expect, it’s also surprisingly easy to understand. In this …

You probably already know how to use Python’s super() to call base-class implementations of methods. But do you really know what it’s doing? The details of super() are elegant, interesting, and powerful, and while super() is probably more complex than you expect, it’s also surprisingly easy to understand. In this …

In this series we look in detail at the behaviour of one of the simplest geometric functions, demonstrate its flawed behaviour when implemented with floating point numbers, and fix it using an exact number type provided in the Python Standard Library.

In this series we look in detail at the behaviour of one of the simplest geometric functions, demonstrate its flawed behaviour when implemented with floating point numbers, and fix it using an exact number type provided in the Python Standard Library.

I noticed that my TV conversion scripts were suddenly running very slowly after upgrading to Lubuntu 14.04. After some investigation it turned out it had started defaulting to using libx264 encoding when the output file was named *.mp4. When I ask it t…

In a recent keynote at RailsConf called Writing Software*, David Heinemeier Hansson argues that test-driven development (TDD) can harm the clarity of our code, and that clarity is the key thing we should be aiming for when writing software. (*contains …

In this series we look at how software architects – or really anyone involved in creating software – can use testability to help manage other quality attributes. From modularity to performance to the SOLID principles, testability can act as a proxy and an enabler for many of the cross-cutting, interacting concerns that …

In this series we look at how software architects – or really anyone involved in creating software – can use testability to help manage other quality attributes. From modularity to performance to the SOLID principles, testability can act as a proxy and an enabler for many of the cross-cutting, interacting concerns that …

Series: What is REST?, A Basic REST API, Paging, Search, Security, Token, OpenID. We are implementing a REST API. Today, adding to the security we already have by making a security token that is stored in a cookie: Slides: Token-based security in a R…

At this week’s ACCU Conference I went to an excellent talk by Sven Rosvall entitled “Unit Testing Beyond Mock Objects”. The talk covered the newer Java and C# unit testing frameworks that allow inserting mock objects even where legacy code is using som…

Consider the following Java code: class FinalInInterface { private static interface WithFinal { public void run( final int x ); } private static class WithoutFinal implements WithFinal { public void run( int x ) …

Recent versions of Lubuntu seem to have broken screen locking. To get screen locking via xscreensaver do this: # Install xscreensaver sudo apt-get install xscreensaver # Start xscreensaver when you log in echo “xscreensaver -nosplash” >> ~/.conf…

Series: What is REST?, A Basic REST API, Paging, Search, Security, Token, OpenID. We are implementing a REST API. Today, providing security using HTTP Basic Authorization: Slides: Security in a REST API. Code: poemtube on github.

Series: What is REST?, A Basic REST API, Paging, Search, Security, Token, OpenID. We are implementing a REST API. Today, we provide a basic search. Slides: Searching in a REST API. Code: poemtube on github.