Over the last two months I’ve been working my way through a handover process as I prepared to leave the company where I’ve been working for the last eight years. This got me thinking a lot about what is a handover and how can it best be executed… What is a handover? The traditional view of a handover is where the employee who is leaving directly trains their replacement(s) in all the aspects of…
I’ve recently been interviewing for a new role. During this time I went through the interview process with three different companies. Two of these I already had in progress before finding the third role (which was the one I really wanted). Each offered a very different approach to the way they structured and conducted their interviews. At the end of these processes I had very different emotional…
In MongoDB (and many other database solutions) scalability is achieved by dividing your database into a number of smaller portions. Each portion is stored on a separate set of database nodes. The theory is that this approach allows your database to scale horizontally beyond the capacity of a single node and allows load to be spread more evenly across multiple clusters of nodes. In MongoDB this…
I've been involved in the Scala community and attending Scala conferences for about four years now. I've just come back from 2013 Scala eXchange , hosted by Skillsmatter in London. It was a great conference, one of the best I’ve been to, and the organisers and speakers should be thoroughly pleased with their efforts. One thing that I did think quite interesting was a significant change in emphasis…
Yesterday evening I was playing a game of 5-a-side football (soccer to my American readers) with some friends. One of the players on my team was a particularly competent player who was also very vocal in offering advice to his team mates on what to do. For example, when a player from the opposing team was approaching me with the ball he would offer sage advice such as "Don't let them get past…
I've spent the last two days on a Fast Track to Haskell course. It was a very interesting two days and I learnt a huge amount. The course was taught by Andres Löh from Well-Typed and hosted by the excellent people at Skillsmatter . I went into the course having read the superb Learn You A Haskell book and having built a couple of experimental Haskell programs. From that starting point there was…
When people usually talk about type classes in languages like Haskell and Scala they tend to be thinking of highly generic concepts like Ordering or Numeric operations. However, in some recent experiments with Haskell I have found that type classes can be very useful for more concrete things. When used appropriately they can lead to more loosely coupled software that is more flexible and easier to…
In my previous post I looked at a simple way to eliminate conditional expressions by encoding them into the Scala type system. In this follow-up post I want to look at taking this further by using the Scala type system to encode state rules. The aim, as always, is to create code that fails to compile rather than code that fails at runtime. By doing this we also reduce the number of unit tests…
I've been at Scala eXchange for the last two days. One of the topics that came up a couple of times was how the type system can be used to encode knowledge and rules, making it possible for the compiler to enforce these rather than needing unit tests to verify them. There were questions from some about how this actually works in practice, so I thought I'd produce some blog posts to demonstrate.…
Here's a little comic strip I put together ... When you have created so many innovative products, it's always going to be difficult to come up with enough differentiation between one version of a product and the next to keep getting people to spend their cash. Creating an entirely new product line is even more of a challenge. I'm wondering where our favourite fruit named company is going to go…
Back in June I presented at the London Scala User Group ( video here ) on our experiences on a recent Scala project that used MongoDB. One of the questions I was asked was how we go about mocking MongoDB for testing purposes (especially unit testing)? My answer was that we don’t! This raised a couple of eyebrows in the audience, but we’ve found this works just fine for us. In this blog post I will…
Just recently I was speaking with a potential customer who had concerns about the velocity of their Scrum teams. They had recently (9 months ago) switched to an agile approach and had expected to get much more delivered than they had. Now they were looking in to scaling up the number of Scrum teams on the project to try and increase velocity and deliver more quickly. In my experience of many agile…
I am happy to announce release 0.5.0 of my xsbt plugin for cucumber. This is a major new update that finally switches from using the Ruby version of Cucumber (running under JRuby) to the newly released Cucumber-JVM. Full details of how to use the plugin can be found on the github page: https://github.com/skipoleschris/xsbt-cucumber-plugin A list of significant changes for this release include:…
In this post back in August 2011 I was talking about the many benefits of Pair Programming. Having now been full-time pair programming for almost an entire year, I wanted to mention one of the downsides that I have discovered. A Holiday I've just finished my holiday. It wasn't the best one ever, mainly due to camping in the UK in June: which meant heavy rain and strong winds. Still, we had a good…
Over the last few years I have been learning and experimenting with a wider range of programming languages. In particular I have started using Scala as my primary development language, adopting a more and more functional style. I have also become very interested in Haskell (a pure functional language) and Clojure (a modern lisp dialect). I have therefore been moving away from the object-oriented…
In my previous post I introduced Dave and we looked at map, flatten and flatMap. In this new episode we take a look at the Scala Option type: Here's some code... case class Person(name: String, partner: Option[Person]) sealed trait Product case object XBox extends Product case class WeekendAway(person1: Person, person2: Person) extends Product type Cash = Int case class Purchase(product: Product,…
I've recently been working with some developers who are new to the Scala world. They've picked up the language really easily and in only a few week have become competent Scala developers. Who says it's too complex and difficult to learn? Anyway, one of these developers is a visual thinker such as myself. We prefer communication through diagrams rather than words. While explaining Scala I've been…
In a recent retrospective our team dug out our Definition of Done and gave it a good review. We ended up removing a number of unnecessary items. This got me thinking about what is Done? In previous places that I have worked the Definition of Done was a long check-list of things that had to have been completed and verified. Is this the best that a philosophy that claims to value "individuals and…
...or, solving problems with lazy evaluation. I’ve recently been working on a simple template system, which also has the potential to grow into a full-blown document generation system. The basic principle is that a document is composed of a number of fragments. Each fragment is called in turn to generate its piece of the document and these pieces are concatenated together to product the final…
I’ve been doing some interviewing of new developers. Our company approach is to undertake a small pairing exercise with the candidate. We pick a relatively simple code kata and ask them to complete this. They drive the keyboard and do most of the work, while we, the interviewer, observe, ask questions, help point out obvious problems and provide assistance if necessary. The only main requirement…
The UK Government today announced a new approach to teaching computing in schools. The current sylabus is based on teaching how to use applications like Word, Excel and PowerPoint. This is, quite rightly, seen as highly boring and unecessary for today's computer literate pupils. The new strategy is to switch to a more 'computer science' based sylabus. This would include more on how computers…
A scenario: you have a successful agile project. It’s made up of a number of small teams, each working on a separate component of the application suite. This has been working extremely well. You are capacity planning for the coming six months and you identify that one of these teams is likely to become a bottleneck. There are just too many stories that fit into their component area. How do you…
In this post and then in this followup , Stephen Colebourne (@jodastephen) states his criticisms of the Scala language and how it feels to him similar to the same feeling of when he was working with EJB2. A colleague of mine also tweeted the following: "This is why I will never use Scala: def ++ [B >: A, That] (that: TraversableOnce[B])(implicit bf: CanBuildFrom[List[A], B, That]) : That" Here's…
Last week Bob Lee ( @crazybob ), from Square , set an interesting coding challenge. All the details can be found here: http://corner.squareup.com/2011/11/luhny-bin.html . I decided this sounded like a bit of fun a set to work on a Scala implementation. I'm pleased with my final result, but also learnt something interesting along the way. My full solution is available on my github account:…
Just recently I was pair programming with another developer and we were writing some unit tests for the code we were about to write (yes, we were doing real TDD!). During this exercise we came to a point where I didn't feel that the changes being made to the code met my measure of what makes a good test. As in all the best teams we had a quick discussion and decided to leave the code as it was (I…