Maintenance

This post is some vague, not-well-thought-out rambling on meta-programming in statically typed languages. As I have said dynamically typed languages tend to have meta-programming already baked in. This is because changing the program itself, doesn’t need to be re-type checked. However, the whole point of a statically typed language is that the program is type-checked before it is run. So you cannot then change the program at run-time because in that case the new program would not be typed. In theory of course you could allow this, but you would have to do one of three things: ...

Update We have started using Constructor which allows us to do exactly this. It doesn’t yet have a ‘public’ issue board, but I believe the developers are working on it. We are a three person team and we use github to store our source code. We also use github to track our issues. There is a missing feature that I’ve never seen in any bug-tracker: relative prioritising of issues. We typically have a meeting after a sprint of work to decide what to work on next. During this meeting we (perhaps after creating some new issues) mark several with the tag “priority”. But what I really want to do, is order the issues by priority. ...

Elm has extensible records, you can write a type like { a | x : Int } which means a record type that has at least a field named x of type Int but may have other fields as well. The general advice seems to be not to use these for data modelling but instead use them to narrow the type of function arguments. See this Richard Feldman talk and, for example, this Charlie Koster blog post. ...

Looking through the code of an open-source Python project I came across code that amounts to the following: host_name = self.connection.getsockname()[0] if self.server.host_name is not None: host_name = self.server.host_name This looks odd because if the condition is True then we forget about the host_name derived from the call to self.connection.getsockname. However it could be that that call has some side-effect. Assuming that it does not we can re-write the above code as: if self.server.host_name is not None: host_name = self.server.host_name else: host_name = self.connection.getsockname()[0] Or even, if you prefer: ...

In many cases whilst programming there is a decision to be made as to whether to store some state, or (re)caluate it as and when needed. Obviously every situation is different and therefore there is no one answer which fits. In this post I’m going to attempt to explain the distinction and the benefits/drawbacks of either approach. I hope that just remembering that this choice exists will force me to make an explicit choice, such that I may think about it a bit more. ...

Dougal Matthews has written a blog post detailing how Vulture can be used to find some dead code. For me this was an important reminder not to rely on coverage analysis to detect dead code and remove it from the your maintenance burden. More generally, whilst I adore automated analysis tools that assist the developer in maintaining their code, such automated analysis can give a false sense of completeness, or lead to the developer believing that their code is “good enough”. It is not a problem I have any solution for though. The rest of the post will try to illuminate this view point through the example of dead-code removal. ...