Mathias Brandewinder on .NET, F#, VSTO and Excel development, and quantitative analysis / machine learning.
by Mathias 19. October 2013 10:33

A couple of weeks ago, I had the pleasure to attend Progressive F# Tutorials in NYC. The conference was fantastic – two days of hands-on workshops, great organization by the good folks at SkillsMatter, Rickasaurus and Paul Blasucci, and a great opportunity to exchange with like-minded people, catch up with old friends and make new ones.

As an aside, if you missed NYC, fear not – you can still get tickets for Progressive F# Tutorials in London, coming up October 31 and November 1 in London.

After some discussion with Phil Trelford, we decided it would be a lot of fun to organize a workshop around PacMan. Phil has a long history with game development, and a lot of wisdom to share on the topic. I am a total n00b as far as game programming goes, but I thought PacMan would make a fun theme to hack some AI, so I set to refactor some of Phil’s old code, and transform it into a “coding playground” where people could tinker with how PacMan and the Ghosts behave, and make them smarter.

Long story short, the refactoring exercise turned out to be a bit more involved than what I had initially anticipated. First, games are written in a style which is pretty different from your run-of-the-mill business app, and getting familiar with a code base that didn’t follow a familiar style wasn’t trivial.

So here I am, trying to refactor that unfamiliar and somewhat idiosyncratic code base, and I start hitting stuff like this:

let ghost_starts = 
         "red", (16, 16), (1,0)
         "cyan", (14, 16), (1,0)
         "pink", (16, 14), (0,-1)
         "orange", (18, 16), (-1,0)
     |> (fun (color,(x, y), v) -> 
         // some stuff happens here
         { … X = x * 8 - 7; Y = y * 8 - 3; V = v; … }

This is where I begin to get nervous. I need to get this done quickly, and factor our functions, but I am really worried to touch any of this. What’s X and Y? Why 8, 7 or 3?


by Mathias 17. February 2012 06:27
I finally finished “Working effectively with legacy code”, reading it a few pages at a time every morning on my way to work. Legacy code is one of these topics you know are important, but which you never really want to hear about, so the book has stayed on the backlog for a while. Recently, I helped out someone establish tests on a legacy code base, and began following Michael Feather’s tweets with great enjoyment, and decided it was time to read it.

Who should read it?

The developer who is already familiar with unit testing, comfortable with his language, object-oriented concepts, and what makes code maintainable - and wants to expand his thoughts and tools on testing and testability.

3 things I liked about it

  • The chapter titles are awesome – just like good naming is a hallmark of Clean Code, the chapter titles convey very clearly what the intent is. “I need to change a Monster method and I can’t write tests for it”, “It takes forever to make a change”, “How do I know that I am not breaking anything”, “I am changing the same code all over the place” – they all evoke situations we have been through one time or another, and the corresponding chapters do address these questions head-on.
  • Clear concepts and vocabulary: if anything, the one sentence that will stay with me is “legacy code is simply code without tests”, a wonderfully clear and opinionated definition, which not everyone may agree with. Feathers defines a few concepts (like a Seam or a Pinch Point), which provide a helpful language to think and and discuss legacy code.
  • Multiple languages: I write primarily in C# and F#, so in principle, learning about specific issues of testing legacy C code isn’t high on my concerns list. Still, I found that going through examples in languages I am not familiar with was interesting, in that it provided both a broader perspective on testing and on the relative strengths and weaknesses of various languages. It also made me think of techniques I seldom (if ever) use in C#, like pre-processor directives.

3 things I didn’t like that much

  • Multiple languages: covering multiple languages provides a broader perspective, but it also comes at the expense of each individual language. If you are specifically interested in, say, C#-specific techniques, this book may disappoint you - it is fairly general.
  • A bit dated: for a book published in 2004, it aged remarkably well. Still, 8 years is a long time in computer-years. From a C# developer perspective, there have been a few major releases of both the language and the IDE, with implications on testing and refactoring. I would assume (hope) that today, most language/IDEs do support refactorings like Extract Method. On the language side, the book touches on using function pointers to achieve decoupling, but the context is mostly C. With the emergence of functional concepts (Func<T> in modern C# for instance), I think this would warrant a bigger discussion today.
  • A somewhat tedious read: this book is not exactly a page-turner. Reading legacy code examples (a good part of them probably not in a language you are comfortable with, unless you are a polyglot) and figuring out mechanical steps to disentangle it isn’t material that will be turned into a Hollywood movie any time soon.

Parting thoughts

I really enjoyed this book, but I would recommend it with an asterisk. Depending on how you want to look at it, a polyglot book will either lose specificity, or gain generality. Personally, I think in this case, the gain in generality easily compensates for the lack of depth in each individual language. Yes, I would like a C#-specific book which points to useful, up-to-date tools – but that book would be obsolete in 2 years at best. By covering a variety of languages, Feathers illustrates very different solutions or ideas, and because he uses only fairly simple features in each language, the ideas remain easy to understand and convert into other “coding dialects”.

My personal bent is for concepts and language, because they last longer than recipes and tools, which is why I really enjoyed this book: it helped me create / articulate a mental map. I don’t have many computer books published in 2004 that I read for insight, today – and this one feels like one of these “timeless classics”.

That being said, I think it takes a certain experience with unit testing and code maintenance to appreciate the book, and I wouldn’t recommend it to someone who is just starting with tests and wants to find quick solutions to their problems. It may work (the book is very clear on steps and methodology), but I suspect it may be potentially frustrating.

Totally unrelated note: this is the first technical book I read on Kindle, and I have mixed feelings about it. I was hoping that the Kindle could serve as a portable library for all these massive technical bricks. On one hand, it’s nice to have the possibility to carry around searchable books; on the other hand, clearly, it’s not the best way to read through code samples, where good old paper still has an edge.

by Mathias 27. May 2009 13:36

The iterative nature of writing code inevitably involves adding code which is good enough for now, but should be refactored later. The problem is that unless you have some system in place, later, you will just forget about it. Personally, I have been trying 3 approaches to address this: bug-tracking systems, the good old-fashion text to-do list, and its variant, the task list built in Visual Studio, and finally, comments embedded in the code.

Each have their pros and cons. Bug tracking systems are great for systematically managing work items in a team (prioritization, assignment to various members...), but work best for items at the level of a feature: in my experience, smaller code changes don't fit well. I am a big fan of the bare-bones text file to-do list; I tried, but never took to the Visual Studio to-do list (no clear reason there). I hardly embed comments in code anymore (like 'To-do: change this later'): on the plus side, the comment is literally tacked to the code that needs changing, but the comments cannot be displayed all as one list, which makes them too easy to forget.

Today I found a cool alternative via Donn Felker’s blog: #warning. You use it essentially like a comment, but preface it with #warning, like this:

#warning The tag name should not be hardcoded
XmlNodeList atBatNodes = document.GetElementsByTagName("atbat");

Now, when you build, you will see something like this in Visual Studio:


It has all the benefits of the embedded comment – it’s close to the code that needs to be changed - but will also show up as a list which will be in-your-face every time you build. I’ll try that out, and see how that goes, and what stays in the todo.txt!

by Mathias 5. January 2009 14:56

I love the class System.Guid, because it has made my life so much easier; whenever I need a unique identifier on a class, I pop in a Guid, and get code which looks something like:

public class Customer
    public Guid CustomerId
        private set;

However, I (painfully) realized today that this also required a bit of discipline. If you have code like this:

public void SetPrice(Guid productId, Guid customerId)
    // do something here

... and have a change of heart about the order of the arguments, you'd better do that carefully, because everything will still compile just fine, even if you don't update the places where that method is called - and figuring out in debug mode what is not working can turn into quite an unpleasant experience. This is one case where you will be REALLY happy to have unit tests in place.


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