About

My name is Christopher Bojarski. I'm a web developer, programmer and blogger. Fan of all things technology related. Avid reader and traveler. Married and living in Philadelphia. Connect with me at cbojar.net.

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The Timeline of Errors

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As software developers, we see errors every day. They manifest as exceptions or segfaults or error codes, telling us that our code has gotten into a state we didn't expect. Their appearance often portends bugs. Though we groan at an unexpected stack trace, we should see an error as a form of automated feedback . Feedback can be fast or slow. We can put the discovery of errors onto a timeline. Errors appear at many points over the lifetime of the code, starting at the moment it is compiled. The further to the right that an error appears, the longer it takes for the feedback to appear. Compile time Compile time is the earliest we can receive feedback about an error. The compiler automatically does a number of checks to make sure the code makes some semblance of sense. The most powerful tool for compile-time feedback is the type-checker. The type-checker makes sure that only values of the expected type are passed around to the places that expect them. This guards
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Name Your Problems

Sometimes when developing code, I run into problems. Ok, a lot of the times I run into problems, but there's a certain kind of problem I run into pretty often. The problem is that I want a thing that doesn't exist. I am writing code, and it is just getting gnarlier and more tangled around a pile of logic. At some point, I hit a wall with it. It is too complicated to really reason about, and I don't want to make things any worse. I've found a trick to solving these problems, though. I take those problems and give them a name. Once I do that, I can get a handle on them, manipulate them, or even sequester them off into a corner. In almost every case, this drastically reduces the complexity back down to a reasonable level, and I often get the side benefit of offering extensibility I didn't know I needed. To demonstrate, let's say we are working on an e-commerce site. The company is based in Alabama, and sells to customers in all 50 states in the US. We have a met
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Assuming the Bugs

Writing code is all about making assumptions. Sometimes those assumptions are explicit, but more often we make those assumptions implicitly. We make assumptions about what kinds of parameters we will receive. We make assumptions about what kinds of values methods and functions will return. We make assumptions about the global state. The correctness of our code relies on the correctness of these assumptions. Bad assumptions can wreck our applicatons. We assumed that method never returns null, but turns out it does. Now we have an unexpected NullPointerException crashing through our stack. We assume that we will always average at least one element. Turns out someone wants to average zero elements. Boom, division by zero, ArithmeticException . We make so many assumptions through our codebases, at least a few are going to be wrong. Really, there are many, many assumptions that are wrong. These are bugs. These bad assumptions are all of our bugs. Usually, our assumptions are i
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